Category: hydroponic growing

Similarly, Cu plays a role as a micronutrient at lower concentrations. On the contrary, high amounts of these two metals once overcome the biophysical barriers in plants become toxic to plants and negatively affect essential biological activities including inhibition of photosynthesis, nutrient absorption and overall plant growth . This could happen after mechanical damage or morphological alterations or indirectly via blocking of aquaporins. It is also suggested that toxic outcomes might be related to reduced syntheses of cell wall components and supplies of essential nutrients . Organ-wise, roots are likely to be most affected by NPs because are the first organ to encounter soil-borne contaminants . We found that Zn was highly toxic to maize plants growing in hydroponics and soil, and that exposed plants exhibited significant reductions  in biomass and chlorophyll, soluble protein, and P contents . In a previous study, ZnO-NPs at 800 mg kg− 1 reduced net photosynthesis by 12% and relative chlorophyll contents by 10% in maize grown in soil for 20 days . Physiological reduction in chlorophyll contents  leads to reduced biomass production . Furthermore, Cu accumulation interferes with the enzymes responsible for chlorophyll biosynthesis and alters the protein compositions of photosynthetic membranes . Reduced chlorophyll yield has been attributed to  reductions in iron content  reduced efficiencies of enzymes required for chlorophyll biosynthesis, and  the replacement of Mg2+ from the porphyrin ring of chlorophyll by metals . Interestingly, at 40 DAS, the inhibition caused by NPs and bulk was smaller than at 20 DAS. This can be related to metal extraction or hyperaccumulator potential of maize plants.

The phytoextraction of maize has also been demonstrated for Zn and Cu . During phytoextraction, plants may undergo some metal induced physiological and/or morphological alterations. These may include compartmentalization of increasing metal concentration in root cell plasma membrane, metal sequestration in vacuoles, stacking pots loading of metals in xylem vessels followed by transportation to upper ground parts and sequestration of metals in leaf cell membrane and vacuoles. Additionally, low-methylesterified pectins of root cell walls can also sequestrate the metals . These many processes can restrict the interactions between bioaccumulated Zn and Cu and maize cellular environment up to certain extent in soil environment. IR revealed that treatments with the tested materials affected biomolecules in roots  more than in leaves . The literature supports our results and suggests such biomolecular alterations in food crops. For example, CuO-NPs reduced the areas of CH2 and CH3 IR bands of lipids , and protein  signal shifting. Rico et al.  suggested C–N–H in-plane bend and C–N stretch vibrations in maize protein after CeO2-NP treatment . The distribution of lipids, lignins, and carbohydrates in maize vascular tissues corresponds to protein distribution patterns , and thus, any change in protein structure by metal treatment might alter lipid and carbohydrate levels and types. Carbohydrate associated IR peaks at 1164–883 cm− 1  can be corelated with bands for pectin in wheat plants exposed to CuO-NPs that resulted in decreased molecular mass of pectin . The low methyl esterified homo-galacturonan fractions of pectin contain free -COOH groups, which are mainly involved in the binding of divalent metals like Cu . Moreover, dissolution of CuO-NPs can be induced by interactions with proteins and organic acids inside plant tissues. Hence, due to strong affinities between divalent metals  and -OH, -COOH, and –SH groups, metal ions strongly interact and modify cell wall polysaccharides . In line with our observations  of Zn and Cu movement through maize organs, Zn deposition in maize roots and shoots was found to be 12–24 times higher over non-treated plants when 500 mg ZnO-NPs kg− 1 was present in soil . In addition, Zn uptake by maize exposed to ZnO-NPs, even during germination, has been reported to be much higher than that of Zn2+ ions , which corroborates with our results of higher Zn uptake in maize organs treated with ZnO-NP compared to Zn2+ .

However, the opposite trend was observed for soil. These observations suggest that Zn uptake by maize occurs mainly by ZnO-NP uptake in soilless medium  but from Zn2+  in soil , though it may be that soil constituents have some effect by hindering the nanoparticle mobility. The higher concentration of Zn in tissues of maize plants grown in hydroponics and soil is also in-line with the results of a study on corn seedlings . Cu uptakes also differed in maize organs when plants were cultivated in different media. Less accumulation of NPs in soil grown plants could be due to the soil derived chemical or physical transformations such as soil weathering, heteroaggregation, binding of NPs with soil organic matter, formation of copper-sulfur complexes, ZnS formation, formation of Cu2O from soil applied CuO-NPs that may limit the uptake of NPs from soil . Cu2+ and Zn2+ caused more inhibition/damage than CuO- and ZnONPs to protein synthesis . Protein inhibition by metals is usually caused by disulfide bond disruption . In one study, Au-NPs severely downregulated 25 genes encoding many essential proteins, including proteins involved in Fe transport, Cu transport, and protease inhibitor/seed storage/lipid transfer, and cytochrome P-450, nicotinamide synthase, and aquaporin . Observed declines in TSP levels in maize after NP or ion treatment could be attributed to the uptakes and translocations of metals even within above-ground parts and disruption of the maize proteome. Phosphorus, a vital plant macronutrient, an integral part of ATP and NADPH  playing crucial roles in major metabolic processes was also found deficient . Shoots generally accumulate more P than roots possibly due to rapid translocation of P from roots to shoots during the vegetative growth phase . In line with our results, nanoparticle treatments have been reported to repress the transcriptions of P metabolism-associated genes, for example, two P-transporter maize genes, GRMZM2G009045 and GRMZM2G326707, were found to be down-regulated by ZnO-NPs .

NPs mediated toxic effects can be associated with oxidative stress . To counteract this, plants have evolved mechanisms to protect themselves from stressors. One such mechanism involves the increased proline production . Proline may be beneficial in maize  by acting as a singlet oxygen quencher and a scavenger of free radicals and other oxidative species  or  by maintaining osmotic balance and homeostasis . Furthermore, a recent metabolomic study revealed that enhanced Ce bio-uptake increased proline levels in beans . Intracellular oxidative stress  in maize induced by ZnO-NPs or CuO-NPs can also lead to apoptosis, recognized as deficit in DNA content  as evidenced by a sub-G1 peak during cell cycle analysis . Similarly, it has been reported that NiO-NPs  caused 65.7% of tomato root cells to undergo apoptosis or necrosis and increased caspase-3 like protease activity 2.14-fold , and in ZnO-NPs  treated wheat plants, NPs induced PI fluorescence in dead or membrane compromised root cells . We observed NPs triggered LPO and antioxidant production in maize plants, which highlights the stress-alleviating potential of maize when grown in polluted environments . Similarly, ZnONPs at 500 mg kg− 1 in soil significantly enhanced LPO and induced H2O2 production in green pea plants . In the present study, the production of formazan in NBT assay was found to be inversely related to nanoparticle concentrations suggesting higher concentrations result in greater dismutation of O2- by SOD enzymes. The O2- as a primary ROS is usually the first reactive species to be released in cells. Subsequently, it is reduced to other ROS  either directly or via metal- or enzyme-catalyzed reactions . Therefore, SOD enzymes rapidly convert O2- to relatively less toxic H2O2. In line with our results of surface and deep scanning by SEM-EDXmapping and TEM , the adsorption and uptake of Fe2O3–NPs in tomato vegetative tissues were reported , and as was observed for CuO-NP  aggregates , hematite and ferrihydrite NPs  were detected by confocal laser scanning microscopy as red spots in maize seedlings .

Entrapping of CuO-NPs and translocation across epidermal cell walls  suggest their uptake by cells via endocytosis-like structures in maize root cortical cells and transportation of NPs follows. For instance, Cu accumulation occurred in shoots of CuO-NP exposed plants but not in CuO-bulk or Cu2+ treated plants . It is worth noting that the Casparian strip  plays an important part in plant protection, but that at the root apex it is not fully developed . Therefore, we suggest that in the current study, NPs passed through root apices to maize steles and were then transported to shoots via xylem. Zn2+ and Cu2+ were more toxic than NPs, irrespective of growth conditions. This could be due to heavy influx of ions in the root apoplast through transporters and metal chelators and enhanced by the negatively charged cell wall due to the presence of cellulose, pectins, and glycoproteins acting as specific ion exchangers. On the other hand, NPs are taken up by plants majorly in nano-particulate form and sometimes compartmentalized in cells. Also, due to quick toxicity by ions, maize plants could not survive for longer. Similalry, grow lights more reduction in Cucumis sativus biomass was evident by Yb3+ compared to Yb2O3-NPs . Additionally, the impact of ions varies depending on the oxidation states. Our results also concur with the findings of Cui et al. , who observed cucumber plants were more sensitive to Ag+ than Ag-NPs at same concentrations. For better understanding the toxic outcomes of Zn and Cu types on maize growth, a comparative table summarizing differences in magnitude of maize growth inhibition by different metal types is presented . Panax ginseng Meyer is a famous traditional medicinal plant belonging to the Araliaceae family. The genus name Panax originates from the word panacea, which means “a remedy for all diseases.” The 4e6-year-old roots of this perennial herbaceous plant are mainly used for medicinal purposes. P. ginseng leaves are palmate, and the flflowers bloom in June.

Ginseng has primarily been cultivated in the forest areas of East Asia including Korea, China, Russia, and Japan. Traditionally, P. ginseng is cultivated in soil, and numerous pharmacological and phytochemical studies of the extracts or compounds from soil-grown plants were conducted. P. ginseng contains ginsenosides, polyacetylenes, sugars, and some essential oils used for enhancement of immunocompetence, nutritional fortification, improvement of liver function, and their anticancer, antioxidant, and antidiabetic effects. More than 70 kinds of saponins have been isolated from P. ginseng. There is a growing interest in using safe, high-quality agricultural products, leading to hydroponic cultivation of ginseng using high-tech culture facilities. Hydroponic cultivation of ginseng takes much less time than soil cultivation and is accomplished in just 3e4 months in a moisture, light, and temperature-controlled environment without pesticide treatment. Hydroponically cultivated ginseng is mainly used in fresh and high-quality ginseng products. The aerial parts of hydroponic P. ginseng are reported to contain higher contents of total ginsenosides than the roots. This study was initiated to isolate active metabolites from the aerial parts of hydroponic P. ginseng. Of note, glycosyl glycerides have never been isolated from hydroponic P. ginseng. Therefore, this study is designed to isolate and identify glycosyl glycerides as well to evaluate their potential for inhibition of NO production. Monogalactosyldiacylglycerol  and digalactosyldiacylglycerol  are commonly present in the chloroplast membrane of ginseng. The MGDG and DGDG constitute up to about 70% of chloroplast lipids.The galactolipids play roles in the photosynthesis and regulation of lipid biosynthesis during phosphate deprivation. Furthermore, glycosyl glycerides were reported to have antifilarial, anticancer, antitumor, and many antiinflammatory activities. Therefore, this study describes the procedure for isolation and identification of four glycosyl glycerides from the hydroponic P. ginseng, and evaluation of their anti-inflammatory activities on NO production in lipopolysaccharide -stimulated RAW264.7 macrophage cells.The root of Panax ginseng Meyer has been used as traditional medicine in East Asian countries for more than 2000 years. Various processed products from P. ginseng have been introduced globally. Panax ginseng has antioxidant and antiinflflammatory properties; thus, it is under investigation for its therapeutic effects on skin disorders, including atopic dermatitis. Intake of red ginseng  extract reportedly attenuated eczema, transepidermal water loss , and skin squamation in patients with AD. Also, an RG extract decreased 1-flfluoro-2,4-dinitrobenzene-induced ear thickness, TEWL, and levels of immunoglobulin E, thymic and activation-regulated chemokines , thymic stromal lymphopoietin, and tumor necrosis factor -a in mice. The beneficial effects of P. ginseng are attributable to ginsenosides, which are the main active compounds in its roots. However, phenolic compounds, including phenolic acids and flavonoids, have also been detected in the fruits, leaves, and roots of P. ginseng aged 3e6 years.

The controlled temperature in S2 results in a doubled yield with respect to on-field cultivation, but still half of the one of vertical hydroponic . Having a high production in a limited space is one of the main qualities of vertical hydroponic systems. Moreover, since no soil is needed, the cultivation can take place in many different spaces: on rooftops, indoor, on abandoned industrial sites, on walls. An additional positive characteristic of hydroponics is that the quality and eventual contamination of the soil does not represent a risk for the products – simply because the two compartments are not in direct contact. This advantage is shown in the agricultural land occupation of scenario S1: by being soil independent and vertical, this type of hydroponics requires from four to 20 times less agricultural land than conventional agriculture. However, this means that hydroponic production needs to be supported by an external input of fertilizers to satisfy the nutrient requirement of the plants. The use of NPK fertilizers in the three scenarios is reported in Table 2. Scenario S1 needs more nutrient input than greenhouse cultivation, but less than on-field production, where part of the applied fertilizers is lost due to leaching processes. The different NPK proportion indicates that hydroponics allows an optimization of nutrient supply to support the growth phases of the plants. These results do not completely explain the impacts on freshwater eutrophication: in scenarios S1 the production of electricity and fertilizers are the main contributing processes, and in scenario S2 the production of heat is the dominant process. Scenario S3 has a negligible use of these inputs, but needs more fertilizers, which determines the emission of nutrients into the water streams.

It is important to distinguish where the emissions of nutrients take place, since eutrophication is a local phenomenon. In this sense, in scenario S1 and S2 the major risk of eutrophication is in the areas where fuels, hydroponic nft metals and fertilizers are extracted, i.e. mining sites distant from the place of final use. On the contrary, in scenario S3 the release of nutrients following the application of fertilizers represents a noteworthy impact on local water quality. About marine eutrophication, the actors in play are the same of freshwater eutrophication , but since scenario S3 has a high release of nitrogen , its impact is higher than scenario S1. Regarding eutrophication, a merit of hydroponics is the efficient use of nutrients, that, by being recycled with the water, are not released through the soil but remain available for the plants. The impact on freshwater ecotoxicity is due to the heat consumption in scenario S2, whereas for the other two scenarios several processes impact with the same order of magnitude: electricity production, fertilizers production, equipment production, pesticide production and transport. The combination of equipment and energy requirements is responsible of the impact of scenario S1 on fossil depletion. Scenario S2, due to the necessity to heat the greenhouse, has a performance more than ten times worse, while on-field cultivation , that is relatively low-input, has half the impact of S1. A benefit of urban agriculture is the shortening of the supply chain and the reduction of losses during the transport of the products. Thanks to the proximity of the farm to the consumers, the vegetables are fresher and do not need to be cooled during the delivery. For these reasons, we assumed zero losses in the transport phase. For conventional agriculture, on the other hand, the reported distribution losses are approximately 12%.The quality of the data influences the results. The primary data collected for scenario S1 refer to four months of production. Even if the farmers considered the seasonal variability for a better estimation of the annual consumptions, e.g. the water consumption, we recognise that the annual estimations could eventually not correspond to the actual values. Moreover, scenarios S2 and S3 are based on LCI datasets representative of the Integrated Production in Switzerland. Even though the authors of the datasets affirm that, most probably, their data are representative for similar cultivations in industrialised countries, these values cannot capture the peculiarities of country-specific cultivation practices. In conclusion, we acknowledge that the data do not have the same level of precision, and this affects the quality of the results.

To compare the performance of the systems, we chose the environmental indicators considered the most representative for LCA analyses of agricultural systems. We recognise that the agricultural sector can deliver other positive and negative effects, such as potential contribution to biodiversity, social issues and economic development. Consequently, integrating the analysis with other methodologies could give a broader perspective on the impacts of agriculture on an environmental, economic and social level.Constructed wetlands are commonly applied secondary or tertiary wastewater treatment systems . CWs exploit natural processes to remove pollutants via substrata, vegetation and microorganisms . CWs were traditionally employed to remove traditional pollutants, but are recently being used to remove micro-pollutants from wastewater. Numerous studies reported the adverse effects of micro-pollutants on human and environmental health . Effects include feminization of fish, short and long-term toxicity to biota, and the development of antibiotic resistance among natural and anthropogenic microbiomes . Currently, phyiscochemical technologies, such as ozonation, and membrane and activated carbon filters are implemented as tertiary treatment to remove micro-pollutants . However, such high-tech, expensive methods are less suitable in many emerging and developing economies . CWs are an attractive alternative: CWs are cost effective, eco-friendly and easy to operate and maintain . However, a key limitation in application of CWs is their high land area requirements, typically termed a land footprint. The CW substratum plays the key role in determining the size of a CW. Substrata remove various pollutants directly by sorption, precipitation, filtration and biodegradation . In addition, the substratum supports plant and microbial growth. Initially, soil was used as substratum. Recently, sand and gravel have been selected for their high hydraulic conductivity, resulting in improved performance of CWs. However, the application of these materials has limitations due to low removal of nitrogen and phosphorous, and more recently for micro-pollutants . Considering the importance of substrata for CW performance, selection of proper substrata could both reduce CW footprint while also removing micro-pollutants. Hydroponic substrata are good candidates for use in CWs.

Developed for hydroponic plant growth in horticulture, hydroponic substrata have attractive properties, such as higher oxygen and water holding capacity, large surface area and retain nutrients . In this study, the use of four commonly used hydroponic substrata were compared: mineral wool, pumice, wood fibre and coconut fibre. To date, a limited number of studies were conducted on their usability in CWs and on their potential to remove micro-pollutants from wastewater . Yang et al.  reviewed the studies which focused on the use of emerged substrata  in CWs to remove conventional pollutants. However, suitability of the emerged substrata to remove micro–pollutants was not reported. Furthermore, Wang et al.  articulated that there is a lack of comprehensive studies available on the suitability of hydroponic CW substrata  to remove various pollutants. Therefore, there is an urgent need to study the potential of the four substrata to remove micro-pollutants in CWs. Generally, sorption is one of the initial removal processes of a pollutant in the filter bed of CW. Sorption is an umbrella term covering both absorption  and adsorption  processes, and is especially used when these two mechanisms cannot be distinguished . Isotherm models, such as Freundlich and Langmuir models can be used to unravel the sorption mechanisms from experimental data to distinguish surface related or absorption related mechanisms.These include physico-chemical properties of a sorbent and sorbate, such as acidity  and hydrophobicity  of a pollutant, and organic matter content of a substratum . These factors influence the affinity between a sorbent and sorbate and transport of the sorbates from bulk solution to sorption sites, influencing extent and kinetics of sorption. Thus, hydroponic channel understanding sorption mechanisms is crucial for successful applications of a substratum in CWs treating micro-pollutant-containing wastewater. This study aims to investigate the applicability of four hydroponic substrata for efficient removal of micro-pollutants from wastewater. We determine sorption affinities and kinetics, and interpret this data using isotherm models and physico-chemical properties of substrata and micro-pollutants.

These results are used to assess the suitability of the substrata in CWs, both for micro-pollutant removal and for reducing CW footprint.Sorption kinetics were studied using the sorption of the micro-pollutants into the substrata over the contact time . Fast initial sorption to organic substrata was observed for most of the studied micro-pollutants during the first 6 h, followed by a slower sorption phase. This suggests diffusion into internal substratum was limiting: rapid sorption to the outer layer of the substrata is followed by slower diffusion in an apparent first order process. Naproxen and ibuprofen exhibited distinctly slower kinetics during sorption to the organic substrata. For inorganic substrata, even slower kinetics were observed for the studied micro-pollutants . A thorough and further mechanistic interpretation of the sorption kinetic data using pseudo-first and second-order models was not possible due to insufficient R2 values resulting from fitting data with these models . The profile of the sorption kinetics  was used to identify equilibrium. The sorption curves levelled off between 24 and 72 h, indicating that sorption reached a status of equilibrium. Based on this, the concentration obtained at 72 h was taken as an estimate of the equilibrium concentration Ce.Organic substrata wood fibre and coconut fibre sorbed micro-pollutants more than the inorganic substrata mineral wool and pumice . The observed sorption affinity of the organic substrata with the micro-pollutants followed the order: trimethoprim>carbamazepine >caffeine>sulfamethoxazole>ibuprofen= naproxen . A similar order of sorption affinity for trimethoprim, carbamazepine and sulfamethoxazole was found for soils by Kodešová et al. . Ibuprofen and naproxen, containing -COOH groups, and sulfamethoxazole, containing -SO2-NH moieties, have acidic protons which can dissociate and form anionic species . Subsequently, a strong repulsion occurs between these anionic species and negatively charged surface of the organic substrata. Although sulfamethoxazole has a basic NH2 group , it has acidic protons due to the presence of an acidic -NHand an electron-withdrawing -SO2- in the vicinity. The presence of two basic NH2 groups in trimethoprim explains its highest sorption affinity. Carbamazepine has one amido group and the basicity of an amido group is lower than of an amino group.

This could explain the sorption order: trimethoprim is followed by carbamazepine. Caffeine has a lone pair of electrons at the non-methylated N site . Therefore, caffeine acts as a proton-acceptor, basic, so it is positively charged and attracted to the negatively charged surface. Caffeine is hydrophilic whereas carbamazepine is hydrophobic due to its dibenzoazepine structure . The hydrophobicity positively affects the sorption . Therefore, carbamazepine is followed by caffeine in the sorption order. The sorption of micro-pollutants on organic rich materials appears to be a trade-off between electrostatic interaction and hydrophobic interactions between the organic matrices and the micro-pollutants. This is further depicted in a four quadrant matrix . In the high pKa and high Log Kow quadrant, both electrostatic interactions and hydrophobicity positively affect the sorption, as indicated by high KF values for carbamazepine on the organic substrata. For the low pKa and high Log Kow quadrant, the positive effect of hydrophobicity of iburprofen and naproxen appears to be largely counteracted by strong electrostatic repulsion due to deprotonation . At the quadrant of high pKa and low Log Kow, an intermediate sorption on the organic substrata was observed for caffeine and sulfamethoxazole. In this study, no compounds falling into the low pKa and low Log Kow quadrant were investigated. We speculate based on our results, that even lower sorption is to be expected for compounds in this quadrant on our selected substrata. Inorganic substrata mineral wool and pumice generally exhibited much lower sorption and slower sorption kinetics towards the studied micro-pollutants. Mineral wool is a non-reactive neutral material. Therefore, unlike wood fibre and coconut fibre, mineral wool has no extensive net negative surface charge. Furthermore, mineral wool has the lowest surface area among all the substrata . These properties together explain the low sorption of the micro-pollutants.

FQs themselves, their synthesis by-products, and the metabolites of bacteria are raising increasing concern regarding their ecological risks . Such compounds exhibit toxicity and non-biodegradability and are expected to form complexes with metal ions and other unknown organic compounds, representing hazardous environmental and health impacts. The resistance capacity of microorganisms will also be inhibited . Constructed wetlands have been used internationally for over two decades in a variety of aquatic enhancement projects . CWs are an important and effective measure used to purify wastewater that can effectively remove antibiotics and pollutants . In the existing research, most of the studies on antibiotics in constructed wetlands address the effects of high concentrations  on the removal of antibiotics, the generation and removal of resistance genes, etc . The effect of antibiotics in the natural environment on the purification of pollutants in constructed wetlands and the influence mechanism are still not known. Moreover, temperature is the key factor affecting the water purification effect of constructed wetlands . The removal rate of selenium by cattail floating systems is 93–100% at 35 ◦C in summer and 51–100% at 5 ◦C in winter . Low-temperature stress has two distinct components: chilling and freezing. Usually, chilling is defined as occurring at temperatures that are lower than the normal growing temperature for a given species but higher than 0 ◦C, and freezing is defined as occurring at temperatures less than 0 ◦C.However, ebb and flow trays the potential threat and impact of antibiotics with respect to the environment cannot be ignored.

Whether different concentrations of antibiotics have an effect on pollutant removal under different temperature conditions and the difference in the influence mechanism are worth investigating. In this study, a hydroponic culture experiment was designed, and the reactors were placed in an artificial climate chamber at 4–8 ◦C and in a greenhouse at 25–28 ◦C . Different concentrations of LOFL were put into the reactors at two temperature conditions. The concentration of 0–10.0 µg/L may appear in the environment, and 100 µg/L is the concentration in emergencies, which can strengthen the impact of LOFL on the entire system . The objectives of the present study were  to evaluate the long-term effects of different LOFL levels on pollutant removal in CWs at low and normal temperatures;  to clarify the changes in the bacterial community structure of CWs after long-term exposure to LOFL at low and normal temperatures; and  to explore the correlation analysis of environmental factors and predict the functional changes at low and normal temperatures. The experiment was conducted in an open field at the China Research Academy of Environmental Sciences , Beijing, China . Plants were hydroponically cultured in white plastic buckets. Each incubator, 191 mm bottom diameter × 214 mm top diameter × 210 mm height, was filled with 4.5 L culture medium . Plants were fixed in planting baskets and incubated with tap water for 2 months in a greenhouse  before the start of the experiment. Hydroponic culture was used in this experiment, and the devices were placed in an artificial climate room  or greenhouse . Plants with similar growth were selected. Four Iris pseudacorus L. specimens were planted in each incubator and fixed with a guardrail. Specimens were cultivated for 81 days, from May 31 to August 20. Temperature was the main factor affecting the degradation of pollutants, and the concentration of LOFL was the secondary factor. The removal rate of pollutants increased with increasing temperature and contact time and decreased with increasing LOFL concentration. The removal rate of NH4+ was greatly affected by the environmental conditions , while the removal rates of TN and TP were less affected by environmental factors, and the removal rate of CODCr was the least affected. Normal-temperature conditions are more beneficial than low-temperature conditions to the degradation of pollutants.

Under the two temperature conditions, there was a significant difference in the removal rate of pollution indices between the control group  and the experimental groups  . The pollutant removal rate of the control group was lower than those of the experimental groups, which indicated that the plants played an important role in the system. At normal temperature, the removal rate of TN was the highest at 0 µg/L LOFL, with a value of 82.90%. Any concentration of LOFL has a certain inhibitory effect on the removal rate of TN. The degree of inhibition of TN removal at a concentration of 0.3 µg/L was lower than that at 0.1–0.2 µg/L, which indicated that the former concentration promoted the degradation of TN compared with the effect of 0.1–0.2 µg/L. Under the condition of low temperature, a LOFL concentration of 0.1–0.5 µg/L promoted the removal of TN by the system. When the concentration of LOFL was 0.2 µg/L, the promoting effect was the most significant, and the removal rate was 73.28%. The degradation of TN was inhibited when the concentration of LOFL was more than 1 µg/L, and when the concentration of LOFL was 100 µg/L, the removal rate decreased to 66.91%. There was a significant difference in ammonia nitrogen removal efficiency between 0 and 0.5 µg/L LOFL and 100 µg/L . Moreover, the difference between 10 µg/L and 100 µg/L was significant. At normal temperature, with increasing LOFL, the removal rate of ammonia nitrogen showed a continuous inverted “V” shape; the tip of the “V” appeared at 0, 0.3, and 10 µg/L, and the removal rates were 85.10%, 87.40% and 77.90%, respectively. The removal rate of ammonia nitrogen was the highest at a LOFL concentration of 0.3 µg/L, and the degradation of ammonia nitrogen was inhibited at other concentrations. When the LOFL concentration was 100 µg/L, the removal rate decreased to 59.99%. LOFL concentrations of 0.1–0.5 µg/L can promote the degradation of ammonia nitrogen, and the maximum removal rate was 45.03%  at low temperature. When the concentration of LOFL was higher than 1 µg/L, it showed an inhibitory effect, and the removal rate was 28.90–30.18%. This result showed that a high concentration of LOFL has a great effect on ammonia nitrogen and inhibits the degradation of ammonia nitrogen. Overall, the removal rate of ammonia nitrogen at low temperature was 17.67–40.96% lower than that at normal temperature. The removal rate of CODCr at normal temperature was 2.06–27.9% higher than that at low temperature.

Under normal-temperature conditions, LOFL at concentrations of 0.1–0.5 µg/L promoted the removal of CODCr, and the promoting effect of 0.2 µg/L was the largest: the removal rate of CODCr increased from 54.63% to 64.78% compared with that of the control group. When the concentration of LOFL was higher than that of 1 µg/L, it inhibited the degradation of CODCr. At 100 µg/L, the removal rate of CODCr was 50.64%. At low temperature, LOFL concentrations of 0.1–100 µg/L promoted the degradation of CODCr. Under the conditions of low and normal temperature, the removal rate of TP in the control group increased from 71.28% to 86.34% and from 83.49% to 92.19%, respectively. Plants played a key role in the removal of total phosphorus. Under normal-temperature conditions, concentrations of 0.1–0.5 µg/L can promote the removal of TP. The maximum removal rate appeared at 0.3 µg/L, and the removal rate was 95.79%. When the concentration of LOFL was higher than 1 µg/L, the removal rate of total phosphorus began to be inhibited. When the concentration of LOFL increased to 100 µg/L, the removal rate of TP decreased to 86.98%. At low temperature, concentrations of 0.1–1 µg/L can promote TP, and when the concentration of LOFL was higher than 1 µg/L, the removal efficiency was obviously inhibited. When the concentration of LOFL increased to 100 µg/L, the removal rate of TP was 80.20%. In this study, the average removal rate of NH4+ at normal temperature was 12.84–55.89% higher than that at low temperature. The average removal rate of TN was 14.71–40.96% higher than that at low temperature. The removal rate of TP was 5.22–12.21% higher than that at low temperature. Studies by relevant scholars have shown that the removal efficiencies of ammonia nitrogen , total nitrogen  and total phosphorus  at low temperatures were reduced by 15%, 45% and 16%, respectively, compared to those observed at the optimal temperature  . Those experimental results are similar to those of this study. At the same concentration of LOFL, the removal rate of pollutants in the system at room temperature was significantly higher than that at low temperature. In this study, the purification of pollutants was mainly due to plant absorption and bacterial degradation . Plants play an important role in hydroponic wastewater treatment systems and directly affect the quality of wastewater . The nutrient absorption mechanism for plant utilization involves plant extraction, 4×8 flood tray plant transformation, plant filtration and plant degradation . Through these processes, plants release exudates from their roots, which can stabilize, fix and bind organic pollutants, thereby reducing biodiversity . This process can further improve water treatment and potentially minimize the discharge of nutrients absorbed by plants.

Existing studies have shown that hydroponic systems can not only purify nutrients but also remove pollutants such as antibiotics . TN removal in hydroponic culture systems is mainly realized by physical precipitation, nitrification/denitrification and plant absorption. However, plant tissue may release and decompose pollutants . Therefore, the mechanism by which plants absorb pollutants and decompose plant tissues is a dynamic process . This study does not conduct an in-depth analysis of this problem. In the low-temperature environment, the removal rate of pollutants in the system was reduced mainly for two reasons. First, plant growth, development, and productivity are negatively affected by low temperatures . Two direct effects at the molecular level would be caused by the reduction in temperature. Enzyme activity and membrane flexibility are reduced with decreasing temperature . When plants suffer from cold temperature, although the photosynthetic light reaction is relatively stable, the activity of dark reactive enzymes is reduced. Therefore, photoinhibition of photosystem I and sometimes II occurs . Membrane elasticity also decreases with decreasing temperature. This decrease leads to membrane damage, which leads to increased electrolyte leakage . The supply of oxygen to Iris pseudacorus L. is restricted at low temperature, and the root activity decreases. These processes lead to the narrowing of voids connected with substrates and air, which affects radial oxygen loss. As a result, reoxygenation is reduced, and the assimilation of nitrogen pollutants is decreased . Therefore, in the low-temperature environment, the nutrient absorption and transformation ability of the plants decreased, resulting in a reduction in the removal rate. The second reason is that the bacterial activity in the system decreased at low temperature. The pollutant transformation processes and mass transfer in CWs were restrained when bacterial activity was affected by low temperatures. Therefore, the efficiency of the ecosystem function limits the removal efficiency of CWs .

The activity of anaerobic ammonia oxidation decreases at 10 ◦C, resulting in the deterioration of nitrogen removal performance . The bacterial activity and metabolic rate in the CW systems were reduced at low temperatures. This reduction impedes heterotrophic bacteria from decomposing organic pollutants . The nitrification reaction efficiency drops rapidly at temperatures of 20–30 ◦C, and the reaction almost stops at 5 ◦C . Denitrification is the most effective way to denitrify  CWs, and the reaction rate decreases at 15 ◦C . With increasing temperature in CWs, denitrification and dissimilatory nitrate reduction to ammonium  increased. After 81 days of culture, compared with the values at 6 days of culture, ace and sobs were larger, and Chao, coverage, Shannon and Simpson were smaller. The higher the concentration of LOFL is, the smaller ace and sobs are and the larger Chao, coverage, Shannon and Simpson are. The ACE and Chao indices indicate bacterial community richness, while the Shannon and Simpson indices reflect bacterial community diversity . Sobs is the actual observation of richness. Therefore, compared with the results at low temperature, the bacterial community richness was higher and the diversity of bacterial communities was lower at normal temperature.This difference might be because the microorganisms were more active in the high-temperature environment and the dominant flora inhibited the reproduction of the inferior flora. In the low-temperature environment, most of the bacteria were inhibited.

Wastewater, groundwater, and surface waters were collected from established monitoring locations in an agricultural watershed containing the City of Jacksonville’s Municipal Wastewater Land Treatment Site , a 2139-ha forest land treatment system in coastal North Carolina, U.S.A, that has treated wastewater since 1998 . The average 30-year annual rainfall is 1379 mm for the watershed . Municipal wastewater land application occurs over 30 km2 of the watershed to irrigate wastewater volumes of 1244 to 1590 mm per year over 890 ha of a mixed hardwood/pine forest. In July 2019, A one-day sampling campaign collected 4-L and 1-L water samples at established watershed monitoring locations for wastewater, surface water, and groundwater; these water samples served as “irrigation sources.” Municipal tap water that was deionized  was amended with Ionic Grow ™ and served as a reference source for hydroponic soybeans.These locations were used for recent multi-campaign targeted , non-targeted , and hydrologic modeling studies . Groundwater and surface water samples were collected using USGS National Field Manual for the Collection of Water Quality Data as described in Hedgespeth et al. and transported on ice prior to storage or processing. All water samples were collected on the same day within four hours of each other in pre-cleaned amber bottles that were triple-rinsed with deionized water and baked for 24 h at 60 °C, then rinsed again with methanol using a modified USGS protocol . One-liter water bottles were extracted within 24 h by solid phase extraction while four-L bottles were stored at 4 °C for hydroponic studies.

Details of representative field sample collection are provided in supplemental documents.Soybean seeds, G. max, flood table were purchased from Johnny’s Selected Seeds  and germinated at 30 °C for four days prior to start of the hydroponic study. Healthy seedlings were randomized and placed in pre-cleaned and methanol-rinsed 250 mL amber wide mouth jars that had been filled with one of the six different irrigation sources. Each jar was covered entirely with aluminum foil and crimped around the plant stem to prevent photo degradation of chemicals in the water . There were three replicates per irrigation source for a total of 18 hydroponic jars and two separate hydroponic studies. One study grew 18 soybean plants for two weeks per USEPA OCSPP 850.4800 method . A second study grew 18 soybean plants for eight weeks until plants produced bean pods and plant leaves began to yellow. The amount of irrigation source water used was recorded while plants grew. At harvest, plants were removed and separated into roots, shoots, and bean pods and weighed as separate entities for wet biomass. Plant tissues were placed on clean aluminum foil and frozen at −20 °C then freeze dried and ground prior to solvent extraction for HRMS analyses.Plant tissues  were freeze dried and cut with clean surgical scissors for solvent extraction. Plant tissue and CIPS samples were fortified with a 100 μL surrogate internal standard  solution prior to extraction . Approximately 1 g of root tissue and 3 g of shoot tissue was extracted by shaking with dichloromethane/acetone  for two hours with a moisture absorbing polymer and then filtered through 0.45 μm PTFE syringe filters. CIPS were first rinsed with deionized water then extracted with the same solvent mixtures by shaking. All samples were processed through gel permeation chromatography  clean up using an Envirogel GPC column  and methylene chloride at a flow rate of 3 mL/ min.

After GPC, plant samples with heavy chlorophyll content were further processed through a Florisil SPE Cartridge  following US EPA method SW-846/3620C  and then eluted with dichloromethane prior to HRMS analysis.We expected that municipal wastewater would have more chemical features, TICs, and ToxCast chemicals overall, but onsite groundwater, surface water downstream of the land treatment site, and tap water had more chemical features for grab samples extracted after 24 h. Mean totals of chemical features in CIPS  were more variable for wastewater and upstream surface water but not significantly different from other irrigation sources . Mean totals of TICs and ToxCast chemicals were similar across all irrigation sources for grab samples and CIPS. Box plot distributions of total NTA features in plant tissues and CIPS show an upward trend from roots to shoots to bean for each irrigation source except surface water downstream of the land treatment site . Soybean roots from off-site groundwater had the lowest mean total of chemical features . Mean totals of chemical features were similar for beans in wastewater, downstream surface water, and tap water and significantly higher than upstream surface water . The mean totals of chemical features in CIPS were not different across all irrigation sources, and mean totals of chemicals features were not different between CIPS and extracted beans for each irrigation source. Mean total counts of tentatively-identified chemicals  and abundance were greater for extracted from roots, shoots, beans, and CIPS than irrigation sources extracted after 24 h . Total counts of TIC numbers and chemical class distributions in roots were most similar to extracted irrigation sources. Roots did contain TICs categorized as cosmetics-personal care products-disinfectants-tobacco . This new class was also present in extracted shoots along with TICs categorized as natural products-toxins, food additives-preservatives, and amino acids-fatty acids-essential oilsvitamins. Not surprisingly, amino acids-fatty acids-essential oils-vitamins and food additives-preservatives were more apparent in shoot tissues than roots, beans, or CIPS.

Chemical class categories for beans were consistent with chemical classes in irrigation sources, but the number and abundance of TICs were two to three times greater in beans than irrigation sources. TICs in beans were different in class distribution and abundance across irrigation sources . Specifically, the number of TICs extracted from beans from plants exposed to downstream surface water and tap water sources were double the TICs extracted from other irrigation sources. TICs in beans from plants exposed to wastewater and upstream surface water remained the same in number and abundance to TICs extracted from each irrigation source. The mean number of TICs in CIPS were more similar to TICs extracted from water, but CIPS had more diverse chemical categories for all irrigation sources than roots, shoot, or beans. TICs for musks-fragrances, hormonespharmaceuticals-drugs, and insect repellents were identified in CIPS across all irrigation sources although these TICS were not detected in irrigation sources, roots, shoots, or beans . There were more ToxCast chemicals  extracted from roots, shoots, and CIPS than extracted from irrigation sources, and more ToxCast chemicals were extracted from municipal wastewater and LTS surface- and ground waters sources than other irrigation sources . However, total count of ToxCast chemicals were not different between CIPS and plant tissues for each irrigation source . Although a qualitative metric and surrogate for concentration, total abundance of ToxCast chemicals in plant tissues were two to four times greater than ToxCast chemical abundances in irrigation sources or CIPS. Surprisingly, mean total counts of ToxCast chemicals detected in plant tissues exposed to municipal wastewater was fewer than mean total counts of ToxCast chemicals detected in soybean tissues from other irrigation sources. For roots, shoot, beans, and CIPS, most ToxCast chemicals were assigned to the Multiple Chemical Use Category across all irrigation sources .

Chemical use categories for CIPS were more diverse than categories for extracted plant tissues and irrigation sources. CIPS had ToxCast chemicals assigned to musks-fragrances, insect repellants, and cosmetic-PCPs disinfectants-tobacco as well as multiple classes, hormones-PPCPs, and industrial plasticizers-fire retardants-surfactants-dyes .We evaluated distributions of TICs and ToxCast chemicals between extracted irrigation sources, plant tissues, and CIPS as a function of log Kow and abundance . At high abundance, irrigation sources and beans had TICs and ToxCast chemicals with log Kow values of 3 to 8 while CIPS had TICs and ToxCast chemicals with log Kow values of 1 to 3. For TICs chemicals at low abundance, log Kow values ranged from 1 to 8 with most TICs above log Kow values of 4 associated almost exclusively with plant tissues or irrigation sources. Likewise, ToxCast chemicals with log Kow values greater than 3.5 were associated almost exclusively with plant tissues or irrigation sources while CIPS had ToxCast chemicals with log Kow values between 1 and 4. CIPS detected more unique ToxCast chemicals from irrigation sources than solid phase extraction of irrigation sources or solvent extraction of plant tissues . There were 11 unique ToxCast chemicals detected in irrigation sources with 1-chloro-3-methyl benzene detected in wastewater, groundwater, and downstream surface waters . There were 13 unique ToxCast chemicals detected in beans with benzofuran detected in beans grown in upstream surface water and tap water and 2,6-dimethoxy phenol detected in beans grown in municipal wastewater and downstream surface water. CIPS detected over 30 unique ToxCast chemicals from irrigation sources . These ToxCast chemicals were frequently detected in multiple irrigation sources and represented more diverse chemical use categories. Only two ToxCast chemicals, hexadecane and 1,3-benzenediol, were detected in an irrigation source, CIPS, and extracted beans, and only 16 ToxCast chemicals were detected in either irrigation source-CIPS, CIPSbean, or irrigation source-bean pairings . CIPS and irrigation sources had more similar ToxCast chemicals for multi-use, industrial,rolling benches insectrepellents, cosmetic, and pesticide chemical use categories with log Kow ranges of 1.3 to 6.2. Extracted beans shared 6 ToxCast chemicals in common with extracted irrigation sources and only 4 ToxCast chemicals in common with CIPS.

The greater number and diversity of chemical use categories for TICs and ToxCast chemicals extracted from CIPS provide more comprehensive representations of chemical use categories for plant exposure and uptake than solid phase extractions of irrigation sources.Historically, agricultural producers have used wastewater to provide water and nutrients inputs to cultivate food crops with positive  and negative  responses of plant productivity due to nutrients, microbiome, and/or phytotoxicity of wastewater . In this study, groundwater irrigation sources yielded poor soybean biomass and no flowering while wastewater and surface waters yielded good growth, flowers, and fruits. Chemical parameters, such as conductivity  and chloride concentrations did not vary greatly for groundwater and wastewater  from prior sampling events. On-site and off-site groundwater did often have low redox conditions, acidic pH, and elevated dissolved iron, manganese, and sulfides that may negatively impacted soybean growth and fruit production . For wastewater and surface water irrigation sources, observed increases in soybean biomass and fruit production did not correlate with mean counts of chemical features or TICs. In fact, beans from plants grown in municipal wastewater had fewer identified TICs and ToxCast chemicals and lower abundances than beans produced from plants grown in municipal tap water. Beans grown in wastewater had fewer TICs and similar ToxCast numbers to upstream surface water, tap water, and surface water downstream of the Jacksonville wastewater site. Downstream surface water and tap water had similar TICs and ToxCast COC numbers, abundances, and types of chemical use categories. The municipal tap water comes from several drinking water plants located in watersheds with significant agriculture, septic systems, and industry. For the study watershed, prior targeted and non-targeted comparisons of organic chemicals for wastewater, surface water, and groundwater provide unique insight to the dilution effect of land treatment systems versus conventional wastewater treatment with dedicated surface water outfalls. Multi-campaign sampling assessments have demonstrated that concentrations of pharmaceuticals in wastewater are often 1 to 2 orders of magnitude greater than concentrations quantified in groundwater and surface water samples during below normal rainfall periods . Pharmaceutical concentrations in on-site groundwater and surface waters are only half-fold greater than upstream surface water or off-site groundwater during rainfall deficits and 1 to 2-fold lesser than concentrations detected downstream of a similar-sized, conventional wastewater treatment outfall . Because the land treatment system stores wastewater in large open reservoirs for 10–14 days and these reservoirs receive rainfall, consistent rainfall events can dilute the number of chemical features in wastewater to equivalent numbers detected in upstream surface waters . Aggregated ToxPI scores of TICs from multi-sampling campaigns were similar for chemicals of greatest abundance between upstream surface water samples and wastewater samples . After a catastrophic hurricane in 2018, the number of chemical features and total abundance in upstream surface water and off-site groundwater samples far exceeded those numbers determined for on-site and downstream surface waters and groundwater at two week and three months beyond the hurricane event .

For the analysis of PFAAs in soil, the soil was dried in an oven at 40  C until no further weight loss was recorded. After homogenization, 1 g of dried soil was weighed in a 15 mL PP tube and spiked with internal standards. The soil was then extracted with 10 mL MeOH by vortex mixing for 1 min and sonication for 10 min. Phase separation was achieved by centrifugation . The supernatant was transferred to a new 15 mL PP tube and concentrated in the Rapidvap. The extraction was repeated twice with 5 mL MeOH. The extracts were combined and concentrated in the Rapidvap to a final volume of 1 mL. For pore water analysis 20 g of the soil was put in a 50 mL centrifugation filter tube with a 0.2 mm nylon filter. After 20 min of centrifugation at 2000 RPM, 0.5 mL of pore water was transferred to a vial. The internal standards and MeOH were added to achieve a final volume of 1 mL. All final extracts were passed through an Acrodisc LC 13 GHP Pall nylon filter into 2 mL PP vials and stored at 4  C until analysis.An HPLC system  coupled with a tandem mass spectrometer was used to analyze the samples for PFAAs. A pre-column prior to the injection valve was used to remove potential background contamination from the LC system. Separation of the analytes was achieved using an ACE 3 C18-300 column  maintained at 30  C with a mobile phase gradient consisting of two eluents A and B , both containing 2 mM ammonium acetate. The gradient used for separation and the mass transitions as well as other mass spectrometer settings can be found in the Supporting Information. The mass spectrometer was equipped with an electrospray ionization interface operating in the negative ionization mode, berry pots and it was run in a scheduled MRM-mode. The purified extracts were diluted 1:1 with water prior to analysis to match the injection conditions of the HPLC. A volume of 20 ml was injected. Raw data were processed with the Analyst 1.5 software .Each sample was extracted three times and each extract was injected in duplicate.

The relative standard deviation of the concentrations derived from these six injections was <10% for all analytes in all samples. Concentrations were quantified using a twelve-point calibration with fitted correlation lines that had r2 values of >0.99 for all analytes; no weighting was applied. Further information on quality assurance and quality control is provided in our previous studies . Recoveries were determined by comparison with a matrix free solution spiked with internal standard immediately prior to injection. Average recoveries of the internal standards in the samples were between 22%  and 112% . Since mass labeled internal standards were used for quantifying the analytes, no correction for recovery was necessary. See Table S4 in the Supporting Information for detailed information on recoveries. Limits of quantification were calculated on the basis of the lowest validated calibration standard. They were derived from the amount injected back calculated to an extract volume of 1 mL and divided by the average extracted sample quantities. Method blanks were prepared repeatedly with the same extraction procedure as the samples, but showed no quantifiable contamination. Solvent blanks were injected every ten injections to check for contamination of the LC system and for memory effects, but no contamination or memory effects were observed during the study. All PFAA concentrations from the non-spiked lysimeters were subtracted from the concentrations in the spiked lysimeters. Any resulting concentrations below the LoQ were neglected. Since PFOS is the only compound for which branched isomers were included in the standards used for the calibration curve, branched isomers could only be quantified for PFOS.

All reported PFOS concentrations are sum concentrations of non-branched and branched isomers.The soil concentrations at the time of planting were generally within the intended concentration range . The soil concentrations at the harvest date show that the shortest chain PFAAs, the C4eC6 PFCAs and PFBS, were depleted. Less than 3% of the initial mass was left in the soil . Depletion occurred in both the upper and lower soil layers . In contrast, some 80e90% of the longer chain PFCAs dosed were still present in the soil at the harvest date. We analyzed the behavior of the PFAAs in the lysimeter soil in another paper in which we include data from 12 other lysimeters prepared in the same manner but planted with different crops . That work showed that the depletion of the shorter chained PFAAs was due to leaching, and that the leaching was greater than anticipated due to interactions between the PFAAs. This accelerated leaching increased with the initial PFAA contamination level of the soil. Lower precipitation towards the end of the growth period contributed to reduced leaching and more stable conditions; two weeks before harvest the lysimeters had already received 91% of the water input for the whole growth period . Hence, although the lettuce was exposed to changing PFAA concentrations in soil, the evidence indicates that the concentrations were more stable towards the end of the growth period when the plants were largest and transpiring  most.To evaluate the plant uptake of the PFAAs, the PFAA concentrations in the plant tissues were compared with the PFAA concentrations in the sampled exposure media, soil and pore water, using uptake factors. Concentrations in soil were only available for the start of the experiment and at the time of harvest, and concentrations in pore water were only available at harvest. We chose to use the concentrations in exposure media measured at harvest because a much larger portion of the plant growth and transpiration occurred during the latter part of the growth period and because soil concentrations were judged to be more stable .

It is nevertheless possible that the uptake factors for the shortest chain PFAAs are somewhat overestimated due to the depletion of these chemicals in the soil over the course of the experiment.Downy mildew  is one of the most severe and devastating diseases for grapevines . Although there are various plant protection products   that can solve this issue, viticulture has traditionally used copper-based products as a fungicide, which is the most efficient way controlling it, and has become an indispensable product for a large number of grape growers worldwide . The reliance on this product is even higher for organic farming since there are no synthetical alternatives accepted to be used and copper-based pesticides are indispensable for organic vine cultivation . Therefore, the continued use of these kinds of products in viticulture has triggered the accumulation of this metal in several vineyard area soils around Europe and worldwide  which may even affect the productivity of food crops . Although Cu is fixed by organic and clayey matter content in the soil, Sonoda et al. observed copper mobility due to organic matter degradation , suggesting possible groundwater contamination. The high potential ecotoxicity of copper in freshwater and its accumulation in European soils have raised concerns in the European Union, leading to a tightening of the legislation on the use of copper-based products, limiting the use to 28 kg/ha of copper for seven years . Even though other PPP such as synthetic organic fungicides could be considered to replace copper in conventional vineyard production, their use is also not exempt from environmental risks such as soil accumulation and surface or groundwater pollution depending on their composition and the site characteristics. For example, hydroponic grow system a recent publication study  observed that synthetic organic fungicides used for grapevine cultivation in northern Italy were present in 80% of monitored water wells, exceeding the Environmental Quality Standards  limits for groundwater in 30% of them. The toxicity of dimethomorph has been observed in several living organisms, such as fish and invertebrates, other soil organisms , soil and water microflora  and aquatic plants . Concerning zoxamide, low risk was observed for non-target arthropods, soil microorganisms, and non-target terrestrial plants .

The increase of organic vine cultivation during recent years has increased the application of other kinds of organic fungicides, those named natural or biopesticides, produced from a natural source  and with minimum adverse effects on the physiological processes of plants , as is the case of laminarin, which is considered to have low environmental toxicity by EFSA . However, although some ecological products are considered good candidates for reducing copper dependency in vineyards, there is no treatment as effective as copper for controlling grapevine downy mildew . The replacement of copper-based products can be done with the use of plant resistance-inducers  or biological control agents,which have no environmental hazards. Henceforth, the use of PPPs such as copper-based and organic fungicides in agriculture can involve a human threat due to the intake of crops cultivated under those conditions  and a negative impact on other non-target receptors such as water, other plants, and animals. In addition, the sustainable use of PPPs in agriculture must include an application rate according to the characteristics of the vegetation and adjusted spraying, in order to reduce product losses due to drift.Despite this, it is worth knowing that active substances of pesticides are washed away by rainfall, causing the deposition of pesticides on the soil , which means continuing to seek solutions for preventing groundwater contamination from agricultural activity. Bare soil, commonly used in low rainfall areas, allows the rainfall water to drag with it the PPPs losses remaining on the topsoil without any obstacles and can even be simulated and modelled . Moreover, erosion and nutrient loss in bare soil would be more pronounced due to torrential rainfall events that are expected to be more recurrent due to climate change. On the contrary, cover crops in vineyards have been proven to be effective in protecting the soil from erosion and nutrient loss, improving soil fertility, structure, soil microbial functional diversity, and balancing the productive, and vegetative parts of the vine.Although the phytoextraction effect of covers in viticulture is not sufficient to eliminate the entire volume of copper annually applied as a phytosanitary product against mildew , cover crops are suggested to reduce the amounts of pesticide leached and, consequently, the risk of groundwater contamination .

Despite this, there has been no research on the effect of covers on the soil leaching of the commonly used organic fungicides in vineyards  . The main objective of this work is to demonstrate the capability of using cover crops in vineyards for the mitigation and prevention of soil and groundwater pollution caused by the application of fungicides. Also, to study if the biodiversity of this cover crops has an effect on it. Copper, 3 conventional/synthetic organic fungicides , and 1 ecological fungicide  were selected. The specific objectives of this work were as follows: i) assessment of the soil type on fungicides leaching, ii) quantification of pollution reduction due to the use of cover crops, and iii) analysis of the vegetation effect on fungicides degradation. Five different PPPs  were selected based on previous trials carried out at OPTIMA project  according to fungicide efficacy against downy mildew in vineyards and lower environmental impact . Table 1 shows the commercial name, register number, the active ingredient, the molecule structure, the octanol-water partition coefficient  and the environmental risk for each of the fungicides studied. Codimur 50 , which is a copper-based product used as preventive treatments, is used as a control/reference treatment due to its preferential use in viticulture against mildew. Forum and Zorvec Vinabel  are novel synthetic organic fungicides, with a systemic action, with dual preventive and curative effect whereas Bion MX  is a synthetic inducer and activator of plant self-defense mechanisms. Finally, Vacciplant is an ecological organic fungicide product. All experimental studies were performed by using commercial fungicides supplied by the manufacturer’s brands or purchased from Agrogava.During the spray application process carried out for crop protection, there is an inevitable loss of fungicides to the ground. According to Gil , the amount of ground losses due to the spraying application process in a vineyard was calculated as 4.62 μg cm− 2 for an application of 1 kg Cu⋅ha− 1 under the worst conditions .

Twenty days following planting, a second application of Urea was made at the same rate. Containers were irrigated to container capacity each day to maintain even soil moisture.Plants were grown in a temperature-controlled greenhouse at California Polytechnic University in Pomona, CA, USA. Containers were arranged in a randomized complete block design with five replications. Temperature was maintained at 27˚C  and 13˚C . Radishes and mustard were grown until bulb formation at 37d. Entire plants were harvested including bulb and leaves. Plants from each experimental unit were independently washed five times in municipal water to remove any soil particles, dust or media. Plants were placed in individual paper bags and dried at 105˚C for 48 h. Dried plant matter was ground and shipped to UCANR lab for lead analysis. Samples were prepared to utilize nitric acid/hydrogen peroxide microwave digestion and lead tissue concentration was determined by ICP-AES as described above. Treatment differences of tissue lead content and other variables were analyzed using Minitab 16 software and GLM and ANOVA with Tukey’s Honestly Significant Difference Test. Salinas Clay Loam  soil was collected from an unfertilized agricultural field in Santa Paula, CA, USA . Cieneba Sandy Loam  was collected from a non-agricultural site in Norco, CA, USA . Soil was added to fill 10 cm round plastic containers: 580 g Salinas clay loam and 620 g Cieneba sandy loam were weighed into containers . Lead nitrate and lead sulfate  were added to soils to produce soils with 600 ppm of lead. Calcium nitrate was added to lead sulfate treated soils at an equivalent nitrate loading rate to account for potential nitrate fertility effects in the lead nitrate treatments. This allows that all plants were exposed to equal amounts of nitrate  while experiencing lead from different salts. Previous germination studies  indicated the extra salinity from Calcium nitrate would not interfere with germination or growth. Radish cultivars “Cherry Belle”, “Rudolf” and “French Breakfast” were seeded and irrigated as described above. In this experiment, plants grown under similar greenhouse conditions, were harvested after 60d, washed and processed as above. The experiment was a factorial design arranged in complete randomized blocks.

The main factors were: Radish variety ; lead source  and soil type . Each treatment combination was replicated five times for a total of 60 experimental units. The data were analyzed using GLM and ANOVA with Tukey’s HSD by Minitab 16 software. Main effects and significant interactions are summarized in separate tables low round pots. A final experiment was designed to examine radish lead nitrate uptake in clay and sand soil textures at different lead loading rates to each soil. All five radish cultivars were used and sourced as previously described. Greenhouse temperatures ranged from 38˚C  to 26˚C . The same sand and clay soils were weighed and measured into containers as in methods 2.2. A concentration range of lead nitrate was added to bring the soil to 0, 150, 300, 600 and 1200 ppm Pb. Lead nitrate was evenly distributed into each weighed soil  and mixed before adding to containers. Seeds of the five radish cultivars were added as before. Plants were grown for 60d and then harvested and washed as previously described. Treatments were arrangedon a single greenhouse bench in a randomized complete block design with a factorial arrangement of treatments using five replications. Dry matter and tissue lead concentration were obtained as previously described and the data analyzed with Minitab 16 software using the GLM and Tukey’s HSD procedures. Soil from the Claremont, CA site was measured at the UCANR lab to contain 158ppm lead. While Red Giant Mustard accumulated more lead that radish cultivars, it did not “hyper-accumulate” than concentrations above the level measured in the Claremont soil. Radish and mustard accumulated more lead in their tissues from contaminated site soil than from soilless media. Radish cultivars were not significantly different from each other in tissue lead content or accumulated lead  All radish cultivars absorbed less lead than Giant Red Mustard.Radish cultivars grown in Cieneba Sandy Loam accumulated significantly more lead in their tissues and had a higher total mass of lead than plants grown in the Salinas Clay loam. Source of lead did not affect tissue lead concentration or tissue lead mass. Cultivars were not significantly different from each other in lead uptake, however, cultivar “Rudolf” grew significantly less biomatter. Interactions between main effects  were not significant.Increasing concentrations of lead nitrate in soil resulted in increased tissue lead and total lead mass accumulation.

Radish tissue dry matter  was not affected by increasing lead nitrate concentration in either soil. Maximum lead accumulation  was seen in the 600 – 1200 ppm treatments. Lead accumulation in radish tissues followed a clear linear increase consistent with concentration increases in either soil type up to 600 ppm lead nitrate. Radish cultivars were not significantly different in their tissue lead concentrations but the tissue lead mass was greatest for cultivars “French Breakfast” and “White Beauty”. Cultivar “Rudolf” accumulated the least lead , but also grew less vigorously than the other cultivars . The effect of soil texture on radish lead uptake was significant ; radishes growing in clay soil absorbed and concentrated less lead in tissues than radishes growing in sandy loam soil. Increasing lead concentration in either soil resulted in increased tissue lead concentrations and tissue lead mass across varieties.While food insecurity in the United States declined from 2008 to 2012, it is still significant—affecting > 15% of the population. Localized food production can reduce food insecurity among vulnerable populations. Much of localized food production in urban agriculture settings takes place in community gardens that have been renovated from other uses or were vacant land. In our study, radishes were grown and harvested from soil obtained from a lead-contaminated site. The site in Claremont contained soil Pb levels higher than allowed by the United States Environmental Protection Agency. The site was a potential community garden and still poses risk to any who would grow and consume food crops from there, especially vegetables such as radish that will accumulate lead in its tissues. While radish cultivars did not vary significantly in their uptake of lead from the Claremont, Ca soil, the hyper-accumulator Reg Giant Mustard accumulated significantly more Pb than radish. Specific data on uptake of toxic metals by plants, especially cultivars within a taxon is lacking in the literature. Our study verifies the potential for one of the most commonly planted vegetables by urban gardeners  to absorb lead from soil. Radish is a non-mycorrhizal member of the Brassicaceae and because of its lack of affiliation with fungal soil partners, it is able to take up metals that would otherwise be sequestered by mycosymbionts. Although radish cultivars did not have lead uptake differences in our first experiment using Claremont, Ca soil, we did find significant varietal differences especially in total lead accumulation in experiment 3.3 with higher lead loading rates.

The varieties “French Breakfast” and “White Beauty” absorbed the most lead and are both lacking in anthocyanin production–they form white tubers. Since anthocyanins can act as metal chelating agents, those radish cultivars lacking anthocyanins may accumulate more lead from contaminated soils. We found that tissue lead concentration was not significantly different between cultivars in any our experiments. Radishes in experiment 3.2 absorbed and accumulated greater amounts of lead than those in experiment 3.3 despite higher soil lead concentrations in the later experiment. This may be because the experiment was conducted in summer with higher daytime and night temperatures. The effect of off-season cultivation and increased temperatures on Brassicaceae lead uptake is not known. Since lead mass accumulation is the product of tissue lead concentration x biomass, significance of the cultivar response to lead mass accumulation in experiment 3.3 could be due to the reduced biomatter accumulation in cultivar “Rudolf” which grew consistently less biomatter in all experiments than most other cultivars. Soils are complex ion exchanging environments. All soils carry a negative charge and thus will adsorb Pb cations. While Pb is considered persistent in soil, this does not preclude its uptake by plants. Clay soils have higher cation exchange capacity and thus adsorb cations onto cation exchange sites. Lead is considered largely immobile in soils, but in sandy soil, particularly when low in organic matter, with neutral to acid soil reaction, Pb may enter soil solutions and thus be taken up by plant roots. In our study, we found greater radish Pb uptake in sandy versus clay soil, consistent with others’ findings. Contaminated sandy soils appear to pose more risk to consumers of vegetables growing in those sites rather than loam, clay, or highly organic matter enriched systems that will better adsorb the Pb cations. Slightly alkaline high CEC soils strongly adsorb lead, and it is less available for immediate plant uptake. Since soil texture affects lead uptake, not all soils pose the same risk to food supplies. Reliance only on soil testing may give inaccurate estimates of what may be absorbed by plants because so many urban soils are modified by adding organic matter, plastic pots 30 liters or importing other soil textural classes that are not mapped. We have shown that radish is a reliable bio-assay plant to detect lead in soil. While analyzing soil directly will give data on possible lead loading rates, it may not accurately predict the amount of lead that will be taken up by crop plants; making plant growth bioassays an important assessment tool. Edaphic conditions such as cation exchange capacity, species of lead present, and presence of sulfur all have effects on absorption of lead from soil. In our study, either species tested, whether highly soluble , or less soluble , were both absorbed by radish resulting in similar lead tissue concentrations. Elemental sulfur may be oxidized in soil reducing soil reaction making metals more available. This would not occur with lead sulfate since the sulfur is already fully oxidized. Metal absorption by radish is more likely affected by soil pH and organic matter percentage and type.

Our findings suggest radish cultivars can vary in lead uptake depending on soil lead concentration, soil type, and their overall growth which is an important factor in the calculation of lead mass accumulated by a given crop. Radish cultivars are not known to be hyper-accumulators but can absorb biologically significant levels of lead from contaminated soil. Hyper-accumulators tend to be rapid and productive growers in the Brassicaceae family and their use in phytoremediation of contaminated sites is well documented.Radish, as well as all farm products, should still be consumed with caution when produced in urban farms with soil lead contamination. This is especially true since the Food and Agriculture Organization and the World Health Organization  determined that “There is no known lead exposure minimum that does not cause IQ  impairment”.Non-human primates are similar to humans in terms of genetic evolution, immunesystem, physiology and metabolism as well as other features.In addition, similarities in cancer genetics between humans and NHPs have been reported, particularly in great apes. Therefore, NHP species are considered as good models for human cancer research. However, due to the low incidence of cancer in non-human primates and the reduced sample size compared to human studies, more data and reports need to be documented, particularly regarding spontaneous tumours. Most studies of cancer in NHPs involved monkeys and great apes. Despite the relevant phylogenetic position of prosimians, few reports of neoplastic diseases have been described in these species. Neoplasia in lemurs has been scarcely reported apart from some primary liver tumors and pulmonary tumors. However, improving our knowledge on prosimian cancer would be useful to trace the evolution of this disease in humans. The current study focuses on a case of T-cell intestinal lymphoma in a female ring-tailed lemur  hosted in Parco Natura Viva, an Italian zoological garden. Prior to 2005 the 5-year old female ring-tailed lemur did not show any clinical sign of illness. In March 2005 a 5-yr-old female ring-tailed lemur, belonging to a collection of 30 lemurs, was evaluated for apathy, in appetence and few episodes of regurgitation. She was thin  and showed abdominal pain during palpation. Hematologic tests did not reveal abnormalities; thus a medical treatment with carprofen  and Joscina N-Butilbromuro was performed.

Water stress is one of the most limiting environmental factors to plant productivity world wide and can be caused by both soil and atmospheric water deficits. Water stress is one of the most limiting factors for plant survival since it regulates growth and development and limits plant productivity. The effect of water stress varies with variety, degree and duration of stress and the growth of the plant. The effect of water stress on yield decrease of rice is very pronounced during certain period of growth, called the moisture sensitive periods.In an experiment conducted in the Philippines. It has been shown that moisture stress early in the growth of the rice reduced tillering, thereby reduced yield. When moisture stress was extended into reproductive phase, yield loss was significant. examined the effect of varying soil water regime during different growth phaseson rice yield. They reported that the soil water stress applied any of the growth phases reduced rice grainyield, compared to the continuous flooding irrigation. The ripening phase appeared to be most sensitive to compared to the other phases. Soil water stress during the earlier growth phases  appeared the production of effective tillers resulting in the reduction of grain yield, while stress during the later growth phases  appeared to affect the reproductive physiology by interfering with pollination, fertilization and grain filling in the reduction of grain yield.

The objectives of this study are to examine the effects of water stress on growth and yield of three rice varieties in Sokoto.Pot experiment was conducted during the 2013 dry season at the Botanical garden of the Department of Biological Science, Usmanu Danfordiyo University, Sokoto. Sokoto State is located between latitude 13˚01′ North and longitude 05˚15′ East of about 350 m above sea level. The area has a long dry season that is characterized by cool dry air during harmattan from November to February and hot dry air during hot season from March to May. Relative humidity ranged from 26% – 39% in the dry season. Minimum temperature ranged between 19˚C and 29˚C and maximum temperature ranged from 30 to 40˚C and, livestock fodder system wind speed ranged between 1.8 to 5 MS−1 . Soil sample was collected from 0 – 20 cm soil depth and analyzed for physic-chemical characteristics. The soil of the experimental area is sandy, slightly acidic, low in organic carbon, total nitrogen, exchangeable cations and available phosphorous .The effect of water stress and variety on plant height is presented on Table 1. The result indicated that water stress had no significant  effect on plant height at 3 Weeks After Planting . Water at tillering resulted to significant reduction in plant height at 6, 9, 12 and 15 WAP. Control  is statistically similar with water stress at flowering and grain filling. The reduction in plant height was as a result of water stress imposed at tillering stage. This is because imposing water stress resulted in law leaf water potentials and reductions in photosynthesis; photosynthetic activity declines because of decreased stomatal opening and the inhibition of chloroplast activity; this reduced the length of the internodes at jointing stage which follows tillering stage. At the time when water stress was imposed at flowering and grain filling, the jointing stage had taken place and plants have reached their maximum height, thus the effect of water stress was ineffective.

Found significant reductions in tillers and panicles numbers as well as plant height and grain yield when water stress was imposed at tillering stage water stress resulted to decreased in plant height, number of tillers per plant, total biomass and grain yield. The effect of variety showed that at 3 WAS varieties did not differ in plant height. But Faro 44 differed significantly with taller plants, while Wheata 4 and Nereca 2 did not differ significantly with shorter plants. The significant differences among genotypes for plant height indicate appreciable amount of variability among the genotypes subjected the varieties to moisture stress at different growth stages particularly during seeding stage. They identified some promising lines had tolerance to the water stress reported varietal differences among the cultivar for moisture stress.The effect of water stress and variety on number of tillers per plantis is presented in Table 2. Water stress at tillering resulted in significantly  fewer number of tillers than water stress at flowering or grain filling and control  which were statistically at par with each other. The fewer tillers recorded at tillering could be as a result of water stress imposed at tillering because non-availability of water at tillering stage resultedin reduction in the amount of intercepted photosynthetically active radiation . Similarly, during tillering plant produces leaves and due to reduced growth as a result of water stress, the leaf initiation gets decreased and thus, tends to reduce tillering. Reported that significant reductions in tillers and panicles numbers as well as plant height and grain yield were found when water stress was imposed at tillering stage. The effect of variety indicated that.FARO 44 differed significantly with higher number of tillers per plant, while FARO15 and NERICA 2 did not differ significantly with fewer number of tillers plant. The significant differences among genotypes for number of tillers indicate appreciable amount of variability among the genotypes. identified promising lines tolerance to water stress.Decrease in HI could be largely due to water stress which resulted to decrease in translocation of assimilates to the grains, which lowered grain weight and increased the empty grains. High HI indicate the efficient translocation of assimilates towards sink.

Lower HI values under water stress at flowering and grain filling stages indicate that it was more harmful in translocation of assimilates towards the grains.The hazard quotients for lead through the consumption of fish and market garden products  are less than 1 in both children and adults. This confirms that the fish species Oreochromis niloticus from Lake Toho in HouinLogbo and Solanum lycopersicum market garden products are not contaminated by lead. The consumption of fish, in particular the Oreochromis niloticus species from Lake Toho in Houin Logbo, exposes the population to the risk of cadmium and arsenic poisoning, while the consumption of market garden products, in particular Solanum lycopersicum, exposes the population to risks cadmium poisoning. With economy rapidly development, gardening has been one of the most important parts of urban infrastructure construction which decorate the city more and more beautiful. More attention is paid to urban construction rather than urban management, which results in low informationized development. This problem has impacted the gardening construction and development. It mainly reflects in the following aspects: 1) Landscaping classification complexity result in difficult management, 2) due to the rapid development of urban construction, information is very difficult to update, 3) traditional management methods can’t accurately statistic various landscaping, such as, old trees, parks, scenic spots, etc, 4) planning and evaluation are mainly based on practical experience. Based on the above reasons, the key technology and construction methods of urban gardening need to be studied and gardening information management system will be studied. By operating this system, the operational level and management efficiency will be improved. Carry out comprehensive evaluation of urban gardening and set urban development strategies for gardening development. Gardening information management system is based on MapGIS data center integrated development platform to build and design on three layer architecture, . The first layer is hardware and software-based layer, which is base for management operation platform. Hardware part includes network equipment, servers, storage, backup devices, network including government special network, Internet, GPRS network, etc. Software part includes operating systems, database management systems, mirror and backup tools, GIS platforms and security software. The second layer is an integrated development platform for data center which is the running environment for gardening information system building and configuration.

The third layer is the applications and services layer which provides business applications and service to users. Integrated development platform for data center is based on the gardening information management requirements, which provides common needs and capabilities. It adopts service-oriented architecture conceptions. It designs and develops corresponding abstraction function module which constituted by several basic function composition. It can be divided into three layers. The first layer is to provide basic and common features, such as basic heterogeneous data view, GIS capabilities, remote sensing capabilities, 3D functions, data processing work space, data security rights management module, etc. The second layer is to provide basic and general landscape features, such as data models management, basic function management, fodder system trays gardening basic method management functions, etc. The third layer is to provide gardening professional functions, such as landscaping assisted analysis, removal and analysis, etc. In addition, as for specific business needs, it provides a standard function module expansion interface, which supports particular business logic integration, specific business function development completion. It can also be incorporated into functional warehouse to be an integral part of a functional warehouse. In addition, data center integrated development module and function module adopts “Loosely coupled” connection approach. This approach which is flexible in structure and powerful expansibility is the best connection method which has minimal environmental impact. Operation adopts “service” approach which converts “data access operation” to “data access service request service”. “Data access service” is an example, which fully embodies the latest “service oriented” design ideas. Digital Elevation Model  is an entity ground model which uses an array of values to describe ground elevation. It’s one of branches of Digital Terrain Model . The other digital model uses matrix form to express various non-terrain features, including the natural and geographical factors as well as the ground-related socio-economic and cultural factors, such as soil type, land use types, rock depth, land, commercial advantages district, etc. By using DEM, 3D visual reality technology, establish 3D view model of gardening planning area, such as urban green space system planning models, landscaping professional planning and green space system detailed planning model, landscape greening proportion and distribution models, urban green space and scenic spots of the planning model. Base state with amendments is one of spatial data management method which doesn’t store all the status of researched area, but only the state of some point and also change to relative basic state. Base state with amendments can greatly reduce temporal data amount. Gardening historical data management is based on tuple level which is based on base state with amendments. Generally, the status after construction of urban gardening is taken as “base state”. User most concerned “current state” is the latest update data state.

All the “current state” gardening information will be effectively managed which can fully reflect the change and development of gardening, and reduce historical data of the redundant and facilitate historical data management. Urban gardening information management system professional basic function includes, greening data model, metadata management, gardening basic function warehouse, gardening basic method warehouse, data exchange components, etc. . The basic function library includes data management basic function library, data update basic function library, data analysis basic function library, 3D model, encoding engine, etc. System application function construction includes application function library, business process library, etc. The application function library includes analysis function library, business function library, thematic map function, etc. Analysis function libraries includes landscaping demolition cost accounting, green analysis, greening comparative analysis, index analysis, etc. Gardening business functions includes gardening project management, landscape planning and management, garden maintenance, etc. Both professional basic and industry function support Visual Studio2005. All the plug-ins development is according to the relative interface standards. After completing plug-in functions, find appropriate registration documents and start editing plug-ins register in accordance with registration standards. Phosphorus is recognized as a limiting factor for growth of aquatic organisms in surface water bodies especially in lakes and reservoirs. When excess amounts of nutrients are discharged into surface water, the biomass of phytoplankton starts to increase and shifts to bloom-forming species that may be toxic to stock animals and potentially humans. As biomass of algae increases, water transparency decreases and taste, odor and water treatment problems become a possibility. Microorganisms decompose algae when they die resulting in dissolved oxygen depletion, death of living organisms, fish kills, and deterioration of aesthetic value of water bodies.

To fulfill their daily basic needs, these people make use of almost any natural resources found in their surroundings. Whereas beneficial species and varieties will be maintained and promoted, less beneficial ones from human perspective will be neglected and replaced by more beneficial introduced species or varieties. The processes of introduction, selection, and substitution are likely to occur at a broad scale as well as a local scale. Consequently, anthropogenic forests are gradually transformed into more productive agricultural systems with lower biodiversity. In Indonesia, agroecosystems play a crucial role in the national production system and are generally dominated by either wetland  or dryland agriculture. In the case of West Java, bamboo-tree gardens are among the most common traditional dryland agroecosystem. Bamboo-tree gardens are locally known as kebon tatangkalan and in parts of West Java as talun, village gardens, or forest gardens. They have a multi-layered structure predominantly composed of a variety of bamboos and tree species, and they tend to have been developed and maintained by rural farmers through many generations. This agroforest has been in existence before 1900s, but nowadays in much of Java, particularly West Java, the area of bamboo tree-gardens has been declining because of the increased use of more intensive market-oriented agricultural practices. In most cases, studies on the bamboo-tree garden system have focused on biophysical aspects of this element of the agricultural landscape. This paper describes the perceptions of bamboo-tree garden owners in two villages of contrasting agroecological conditions within the upper Citarum basin with regard to the management of this traditional agricultural system. Perceptions relating to bamboo-tree garden management are important to the future sustainability of this socioeconomically and ecologically important traditional system.

Parikesit et al.pointed out the ecological importance of this agroforestry system by the fact that, nearly 80% of the bird species encountered in the study sites were found to use bamboo-tree garden patches as habitat. Some of the species found in bamboo-tree gardens are protected by the Indonesian law because of their rarity,hydroponic bucket ecological importance, and/or endemicity. In addition, bamboo-tree gardens also perform as a direct and indirect socioeconomic function such as providing food, fiber and fuelwood for local people. We expect that the results of the study described in this paper could and should be used to guide policies on the conservation of bamboo-tree gardens in the upper Citarum basin. Conservation efforts are necessary not only because this landscape element has an important ecological role and high biodiversity, but also because many low income rural people depend on the bamboo-tree gardens for fuelwood as their only source of energy.For each question, the answer was scored from 1 to 7, ranging from very negative  to very positive perception . The score for every answer inevitably contained an element of subjectivity on the part of interviewers. Therefore, a probing questioning technique was used during the interviews. Where doubtful scoring occurred, the interviewer had to return to the respondent to clarify ambiguous answers. A single interview could last more than 2.5 hours. Information on agricultural land ownership and social parameters such as education level and main occupation were also collected. The questionnaire was divided into several categories related to the owner’s perceptions of their bamboo-tree garden or, in some questions, bamboo tree-gardens in the village . These categories were  garden ownership;  the socioeconomic, cultural, and ecological functions of the garden;  management of the garden;  recognition of any decline in bamboo-tree gardens in the village and causes for that decline; and  the outlook for preservation of the gardens. Some of these categories consisted of several subcategories . For example, the first category, about the general attitude to owning a garden, consisted of three subcategories pertaining to socioeconomic status, cultural meaning, and economic benefit. The 56 questions were classified into each subcategory, and 33 major questions were chosen to reflect the major aspects of each category or subcategory. The codes used for the 33 major questions and a brief explanation of each major question are shown in Table 2. The remaining 23 questions were to provide supporting information related to the major questions and/or additional perceptions of the respondents. Semi-structured interviews were also carried out with former owners and other relevant informants, such as the village leader, local farmers, and fuelwood gatherers, to cross check the answers given to particular questions by bamboo-tree garden owners.

Secondary data were collected from various sources including previous studies conducted at the present study sites. Data on the general characteristics of the villages were obtained from the village office. We performed principle components analysis  of the perception scores. Eight respondents from Wangisagara did not answer all of the questions, so the answers of 58 respondents  were available for analysis. The respondents’ scores on each PCA axis were correlated with external factors such as the area of agricultural land owned and education level obtained to determine causal relationships between perceptual rankings and external factors. Kendalltau rank correlations, a nonparametric measure of the degree of correspondence between rankings, were also calculated. The trends in respondents’ perceptions obtained from the PCA differed between Wangisagara and Sukapura. We tested differences in perceptions of the bamboo-tree garden owners between the two villages using the Mann-Whitney U-test on the responses to the 33 major questions as well as to some of the supporting questions. All statistical analyses were performed using SPSS 10.0 .The principle components analysis  on the data set with 33 variables and 58 samples yielded five principle components or axes that had eigenvalues > 2. The eigenvalues for the first to the fifth axis, in order, were 5.25, 4.31, 2.90, 2.41, and 2.23 . Together, these five axes accounted for more than half the total variance . Factor loadings for each variable or question in the five axes calculated by PCA are shown in Table 4. Correlations between the five principle component scores and agricultural landownership are shown in Table 5. The size of bamboo-tree gardens was significantly positively correlated with the first axis and negatively with the third axis. The size of paddy fields was significantly positively correlated with the first axis and negatively with the second axis. The area of paddy fields was significantly positively correlated with the area of bamboo-tree gardens and negatively correlated with the area of upland fields. The latter correlation is understandable because respondents who owned paddy fields were predominantly in Wangisagara where there were relatively few upland fields . Figure 1 shows the factor loadings for the 33 questions and the principle component scores of the 58 respondents for the first and second components although the cumulative explanation of variance was about 30% for these two components. The scatter patterns of the respondents were different for the two villages; respondents from Wangisagara had larger scores on the first axis and smaller scores on the second axis than those of Sukapura.

Although the difference in the scores of the two villages for the first axis was not significant , the scores of Wangisagara tended to be higher, and there was a significant difference between the villages for the second axis . There were no significant differences for the third and fourth axes , but the fifth axis was correlated with the size of upland fields,stackable planters where Sukapura had higher scores . Regarding the relationship between social parameters  and principle component scores for each respondent, there was no significant relationship for the three educational levels: no education, completed primary school only, and completed higher school . The PCA scores of respondents whose main occupation was farmer were significantly higher on the second PCA axis than those whose main occupation was non-farmer . Since all seven non-farmers belonged to the village of Wangisagara, we compared the relationship between the scores of the second axis with occupations of respondents of that village only; there was no difference. This means that the perceptions of respondents were not influenced by either educational level or main occupation. Along the first axis of correlation with the area of bamboo-tree gardens, perceptual categories such as economic and ecological functions of the gardens , management knowledge to improve productivity of the gardens , and willingness to preserve the gardens, especially with economic improvements , had higher values. The axis reflected generally positive perceptions on the existence of the gardens and indicated an economic dependency on the gardens. Regarding the second axis, perceptual categories having higher values were those that referred to management frequency, especially of the more intensive activities such as pesticide input, weeding, and tree management . Other categories with higher scores included the amount of time spent on maintenance , social functions , and awareness of the decline in the garden through conversion to cash crops . Scores with lower values were for socioeconomic status of the garden’s owner , maintenance cost , need for marketing support to increase produce values , and need for governmental support programs . The second axis would therefore indicate intensification of the management of gardens. Respondents who had higher scores along the axis presumably managed their own gardens intensively, while those who had lower scores were likely to depend on sources of income other than their bamboo-tree garden. For the third axis, which was significantly negatively correlated with the area of bamboo-tree garden, the questions with the five highest factor loadings were E2-1, B1-2, D3, E1-2, and D0, whereas the five lowest were A1-1, A1-2, A3, B1-3, and E1-1 . Since there were positive perceptions on garden ownership in a negative direction, the axis explained the degree of negative perception for social and economic categories. For thefourth axis, the five highest categories were C3-1, C1-5, C1-3, C1-1, and E2-2, whereas the five lowest were B3-2, B3-3, B2-2, B2-1, and D0 .

The association of perceived garden decline with positive perceptions on frequent management activities or with positive perceptions on social and ecological functions could indicate a perceptual contrast between whether the garden is seen as a part of nature or a part of the agricultural system. Finally for the fifth axis, which was significantly positively correlated with the area of upland fields, the five highest perceptual categories were D2, B3-1, D1-1, B3-4, and D3, whereas the five lowest were D0, A2-1, A2-2, B2-2, and B2-1 . Considering that the respondents of Sukapura had significantly higher scores on this axis than Wangisagara, it would appear to explain a perceptual difference. The farmers in Sukapura appear to recognize and accept a general garden decline for economic reasons, whereas those in Wangisagara appear to be alarmed by the decline because of the gardens’ longstanding role for subsistence and particular social functions.The responses to the two questions probing the self-perception of wealth and social status of bamboo-tree garden owners had consistent factor loadings on each axis  for the first 2 PCA axes. For both questions, the mean values of the responses were higher in Wangisagara than in Sukapura . This difference suggests that the owners in Wangisagara village had more positive perceptions on the value of bamboo-tree gardens as an important asset indicative of their socioeconomic status within the village. Their perception was also confirmed by direct observation of their material possessions during the interviews and statements from key informants that bamboo-tree gardens are usually owned by families of the property owners of their village for generations. From the perspective of traditional and cultural perceptual categories, respondents in both villages had strong positive perceptions of the bamboo-tree garden as an important family asset inherited from their ancestors and that they in turn should leave as an inheritance to their descendants . On the latter question, the score was higher in Wangisagara . The income from the gardens in both villages was not large enough for most respondents to accumulate savings. Despite this, owners in both villages still had positive perceptions about the economic benefits of theirbamboo-tree gardens . Moreover, all respondents regardless of village provided a rank of seven to a supporting question about whether the amount of garden products was sufficient for their own consumption needs. The economic importance of owning the gardens was particularly well recognized in relation to subsistence.

The maximum acceptable levels of B. cereus in food vary slightly between countries, but in general concentrations between 3 and 5 log10 CFU g− 1 are considered satisfactory and above 5 log10 CFU g− 1 unsatisfactory . Another important factor to consider/include in our study is that after the nitrification process, preceding the introduction of the biofertilizer in the hydroponic growth system, the levels of B. cereus was monitored to 1 log10 CFU/mL indicating that this process might lower the initial high concentration to acceptable levels. The continuous presence of low levels of B. cereus throughout the challenge tests however indicates that the biofertilizer has a capacity to act as a reservoir for B. cereus spores and this is a critical factor to consider in each risk assessment for this product matrix. The bacteria’s ability to form spores  provides an explanation as to how it can be present after hygienization and anaerobic digestion of the biofertilizer, and also to how it can be steadily present in the biofertilizer in the challenge test experiments despite a large amount of the inoculation dying off after a very short time after incubation. The fact that S. enterica and L. monocytogenes do not establish themselves, even seemingly dying off within 48 h after incubation in the biofertilizer, implies that the biofertilizer constitutes a highly inhospitable environment for these food-borne pathogens. In the case of still having viable but non culturable cells, a calorimetric measurement where the biofertilizer was inoculated with the pathogenic bacteria was performed in parallel with the selective plating. As well as the non-supplemented control samples in Section 3.1, these samples showed no signs of microbial activity , which corresponds to the results from the selective plating. The apparent lack of nutrients supporting microbial growth in the biofertilizer  could be hindering the establishment of these pathogenic bacteria. This is supported by the findings in the accelerated microbial activity assessments in Section 3.1 where growth was only obtained after supplementation of BHI.

This is also in line with a recentstudy by Fern´ andez-Domínguez et al. who reported that non-biodegradable compounds increased largely after anaerobic digestion. Besides the lack of available nutrients, the chemical composition of the biofertilizer could exert an additional inhibitory effect on the establishment and survival of the food-borne pathogens. The pH of the biofertilizer was measured initially and was between 5.8 and 6.1, thus the pH of the biofertilizer should not be hindering the establishment of the bacteria. A previous chemical analysis of the presence of PPCP’s  in the biofertilizer , shows that the samples collected from local Swedish biogas production plants  may contain considerable levels,nft system exceeding 100 ng g− 1 of fenbendazole, however this compound is not reported to have any antimicrobial activity . Antimicrobial agent sulfaclozine was detected in low concentration, which might very well have an impact on the establishment of the pathogens. Theobromine, an antimicrobial bitter compound  found in cocoa was detected in levels of μg g− 1 , and caffeine was found in similar levels, which also might have an effect in hindering the establishment of the pathogens. Fungicides propiconazole, fludioxonil and imazalil were detected in considerable amounts, ranging from 100 to 900 ng g− 1 . It is possible the presence of these compounds and/or other inhibitory compounds produced by methanogens during anaerobic digestion in the biogas production plants, in combination with the apparent lack of nutrients, make the biofertilizer a non-growth-supporting environment for the food-borne pathogens to survive. Previous studies on the microbial community of anaerobic digestates reveal that the results vary widely depending on the composition and treatment of ingoing substrate, conditions of digestion, and variable region chosen to be sequenced, however, most studies conclude the most dominant phyla to be Firmicutes, Bacteroidetes, and Proteobacteria . The general focus in sequencing of biofertilizers in previous studies has been on plant-growth promoting microbes, with less focus on risks regarding human health in the utilization of biofertilizer for food production. The purpose of this study was thus to consider the information from the microbial community analysis from a food safety perspective. The library preparation of the 16S rRNA gene amplicon sequencing yielded low amounts of DNA  for all samples except for the samples of non-nitrified biofertilizer  and the starting sample of nitrified biofertilizer  .

A negative control was also included in the library preparation. The 25 most abundant genera across all samples can be observed in Fig. 4A. If no genus level classification could be obtained, the lowest assigned taxonomic classification was given. In addition, the phylum level classification was given . The microbial communities of the samples were also analysed with multivariate statistical analysis , demonstrating the similarity in microbial community between the samples, as can be observed in Fig. 4B. The 16S rRNA gene amplicon sequencing revealed that the most abundant genus within all the samples of nitrified biofertilizer from the hydroponic channels was Mycobacterium . This genus could not be detected in the samples of nonnitrified biofertilizer or the inorganic fertilizer. Since it is also present in the Day 0 sample , a transfer or contamination from the plant roots to the biofertilizer can be ruled out. Seeing that the nitrified and non-nitrified biofertilizer differ so drastically in the microbial community composition, as can be observed in the principle component analysis, it is apparent that the nitrification process, including lowering of the pH from 8 to 5.5, aeration, and changes in the composition of nitrogen compounds, affects the microflora present. Mycobacterium are known to be hardy bacteria that have acidic tolerance and resistance to disinfection, and can survive and grow in a low organic carbon environment.Since it is not detected in the non-nitrified biofertilizer it indicates that it emerges in the biofertilizer in some step after nitrification, however a count of 0 in relative abundance might not mean that the genus is absent, but that it is below the limit of detection . Regardless, finding Mycobacterium in a sample such as the biofertilizer is not unreasonable as they have been found to be common in cattle manure and in water distribution systems, and can survive there for long periods of time . It is also not such a surprising result to find this genus in the nitrified biofertilizer considering that species within the genus are denitrifying bacteria, and can rely on nitrate as an energy source during anaerobic conditions . While Mycobacterium tuberculosis and Mycobacterium leprae are well-known pathogenic mycobacteria, several species of environmental mycobacteria can also be opportunistic human pathogens , and a further investigation of species level would be interesting in theaspect of ensuring microbiological safety in the utilization of this biofertilizer for production of food.

In the non-nitrified biofertilizer the most abundant genera from the16S rRNA gene amplicon sequencing were Pseudomonas, Leuconostoc and Sporosarcina. Pseudomonas and Sporosarcina are naturally found in soil , and Leuconostoc is normally found widespread throughout the environment, in fermented foods and in plant matter.The microflora of the nitrified biofertilizer also varied between the samples taken at the same timepoint but from different channels; in comparison the samples of the inorganic fertilizer are much more clustered and vary less between samples. This behaviour can be connected to the variance shown between samples from the viable count analysis in Section 3.1, where the microflora differed in different replicates of the same kind of sample, and also from the discovery that some members of the microbial community exert antagonistic behaviour towards others. In the inorganic fertilizer, the most abundant genera were Lactobacillus, Enterococcus, Serratia, and Pseudomonas. The high relative abundance of OTUs detected in the negative control in the samples is a result of the low DNA yield of the samples , rendering the sequenced background more prominent. It was concluded that these genera cannot be distinguished to originate from the sample or the sequenced background. The genera can originate in the sequenced background as the ingredients of the PCR reaction of the sequencing may contain bacterial DNA, which is a common occurrence. . It was furthermore not expected to have high yields of DNA in the inorganic fertilizer. In the inorganic fertilizer the most abundant genera were Lactobacillus, although this was also the most abundant in the negative control and is believed to be sequenced background, Enterococcus, also present in negative control but in generally lower abundances, Serratia, also present in negative control, and Pseudomonas present in negative control but in very low relative abundances. The low DNA yield from the biofertilizer samples was a quite unanticipated result as the biofertilizer was expected to have a rich microflora as a result of the anaerobic digestion. If the nitrification process that the biofertilizer undergoes was the culprit for the reduction in natural microflora, it would at least have been expected to find some genera of nitrifying bacteria in the 16S rRNA gene amplicon analysis. As this was not the case one explanation is that the apparent lack of factors for growth, as is fortified by the findings in the microbial activity assessment of the biofertilizer in Section 3.1, has simply reduced the types of microorganisms that can survive to very hardy bacteria such as Mycobacterium or spore formers that can endure in the low-carbon environment that the biofertilizer constitutes. In a study of the microbial community of soil, hydroponic gutter it is found that the low DNA yield is in fact a result of poor growth rather than an inadequate DNA extraction .

It is also reported that low DNA content might introduce bias in 16S rRNA gene amplicon sequencing analysis, which is an important parameter to keep in mind when drawing conclusions regarding the composition of the microbial community . Food security has been one of the main concerns of the countries that depend on imported food, for instance, the Middle East countries like Qatar and United Arab Emirates. Full dependence on fresh food supplies from other cities or overseas has negative effects on food security. Shortages of fresh vegetables in some cities during the Covid-19 lockdown period have forced the government to reconsider its sources of fresh vegetables. Hydroponic systems are recognized as being among the main technical approaches to providing sustainable food and reducing pressure on agricultural land by shifting food production to urban environments. For instance, the state of Qatar imported approximately 90% of its food until 2017 and has been encouraging the firms to develop hydroponic farms to satisfy the country’s food demand. Hydroponic systems provide water-efficient food production but they are not an energy-efficient solution. This is because they require electricity for heating and cooling, ventilation, irrigation, LED lighting, and other horticultural practices to maintain the hydroponic farm operations in controlled environments. The huge energy consumption of the hydroponic system not only leads to an increase in operating costs but also environmental pollution. The industries are required to reduce the carbon emissions to achieve the 2 ◦C global warming target by adopting clean energy. In order to enhance sustainability when addressing the aforementioned challenges, governments must seek innovative solutions to achieving sustainable supplies of fresh food and energy supply. The photovoltaics presents a promising technology that can provide a portion of the clean energy needed to meet the huge electricity requirements of hydroponic farms. Fig. 1 illustrates a hydroponic system with solar energy generation. First, a timer is set such that irrigation starts at specific time intervals. At the appropriate time, the system starts performing irrigation using a reservoir that contains nutrient-rich water. The water-nutrient solution is pumped into the bottom of the growth tray where plant roots are held. The plant roots absorb some of the water-nutrient solutions and the rest is returned to the reservoir, where it can be used in the next irrigation process. Therefore, there is a recirculating system. These hydroponic systems are intended for use in closed buildings that are automatically irrigated, ventilated, cooled and heated, and illuminated. The energy required to run the various crop illumination equipment is supplied through a dual system in which regular grid energy is supplemented by solar power generation.

Fish weight was recorded monthly by extraction of all animals from each tank. In this process, changes in total biomass of fish were determined to calculate different growth parameters as average daily growth rate , specific growth rate and feed conversion ratio , according to Lobillo et al. . Average fish weight was calculated by dividing the total fish weight  by the number of animals. ADGR was calculated as the ratio between average fish weight  increment and elapsed time. SGR was calculated as 100 x. FCR was computed as the ratio between consumed feed and total fish weight increment . Tench were fed with a trouts’ starter feed from the company “Biomar” with 54% protein and 18% fat. Animals were fed twice a day applying an amount equivalent to 1.5% of total biomass, therefore modifying the quantity of feed provided after each fish weighting. The following parameters were analysed daily: ambient and water temperature by means of a maximum-minimum thermometer  and the volume of water replacement due to evaporation and transpiration water losses. Daily water replenishment rate was calculated as the ratio between the average daily consumption and the total water running in each system. Water samples were collected weekly from the fish tank in order to measure pH, electrical conductivity  and nitrates. The pH and EC were determined with a pH-meter GLP 22 and an EC-Meter BASIC 30 ; respectively. When the pH of the water dropped rapidly to values close to 7, sodium and potassium hydroxides were added to the sump until it reached a value above 7 again. Nitrates concentration was obtained by means of an RQflex 10 plus . Dissolved oxygen levels were determined using colorimetric test kits . Aquaponic systems usually show low concentration levels of elements such as K, Fe or Ca. Therefore, the plants were periodically examined to observe the occurrence of nutrients insufficiency. To alleviate these potential deficits, K2SO4 at 1.5% was foliarly applied in all aquaponics systems. The applications were performed twice a week , first thing in the morning with a manual sprayer.

Chelated iron solution  was directly added to the water , 0.1 L for each system. This was done on Fridays every fortnight. The effect of the substrate type used in the aquaponic production of strawberry,rolling benches bare roots and rockwool, on studied variables was assessed by means of an analysis of variance . Since multiple, repeated measurements were made in an experimental unit in our experimental design, a “repeated measures structure” was considered. In this design, the observations can no longer be considered to be independent, and as a result, we assumed that there were correlations in the residual errors among time periods. A mixed general linear model , considering substrate type as fixed factor and sampling time  and block as random factors, was performed with the STATGRAPHICS Centurion XVIII statistical package . Previously, the normality and homoscedasticity were checked with the SmirnovKolmogorov test and the Levene test, respectively. The best transformation meeting normality criteria was obtained by means of Box-Cox transformation using the same software. In all the cases, with this power transformation, normality and homocedasticity were met. Post hoc analysis was performed using the HSD Tukey test and differences were considered significant when P < 0.05. When interaction between factors was found to be significant, the effect of main factors could not be discussed since this means that a substrate has an effect that changes along the sampling period. In these cases, the evolution along sampling period was described and compared between the two substrates studied. Despite the fact that the air temperature presented important variations within the greenhouse , water temperature in fish tanks underwent lower deviations, ranging between 17 and 28.1 ◦C throughout the period in which this test was performed . In general terms, the three systems studied were very similar with regards to the studied parameters of water quality. Nitrate content of the water increased from initial values around 20–30 mg L− 1 to values higher than 70 mg L− 1 after 42 days from the start of the test .

In this same period, pH decreased from initial values close to 8, similar to those corresponding to the available water source, to values between 7.2 and 7.6 as a consequence of the activity of nitrifying bacteria. In order to stabilize both parameters, the accumulated amount of water added to the system was increased from 49 days since planting . At the end of this trial, the daily water replenishment rates for systems 1, 2 and 3 were 2.16%, 2.21% and 2.22%; respectively. In relation to the electrical conductivity of water, the variations observed in Fig. 5 were analogous to those followed by the nitrate content as a consequence of the above referred water replacement operations. Weekly measurements of the dissolved oxygen levels showed stable values , which are considered adequate values for both fish and plants. Initial fish biomass in each of the three tanks was around 700 g, with 122 animals per tank  and average weights per fish were between 5.71 and 5.76 g. After an acclimatization period of 30 days, average fish weights increased to 6.46–6.47 g, reaching 10.93–10.97 g at the end of the trial. Average daily gain ratios  ranged from 0.023 and 0.025 g day− 1 at the initial period to 0.074–0.081 at the end, with a global value for the full period of 0.057 g day− 1 . Specific growth ratios  recorded at the same dates varied from 0.383 to 0.408–0.749–0.833% day− 1 , with global values of 0.707–713% day− 1 . Feed amounts supplied to the animals were increased as they grew, so that during the first month they were given 195 g, in the second 359 g and in the third 420 g, which meant a total consumption of 974 g per tank. According to the feed consumption and the weight gained by the fish, the feed conversion ratios  were calculated, with values in the range 2.22–2.32 during the first 30 days and 1.48–1.61 at the end of the trial, with global values of 1.53–1.56. The mortality rate of the fish was very low, since only one animal died in one of the three tanks studied in this trial. As happened with the water quality parameters between the three tanks shown above, there was a great uniformity in the results obtained for the different parameters related to the growth of fish in the three tanks. No discordant data were found for average weights at different ages, average daily growth rate, specific growth rate; mortality, or feed conversion ratios. Almost all the plants in the trial were able to produce fruits during the study period, as it can be observed in Table 2. Total production per plant varied between 0 and 105 g, where zero values indicate that the plants did not produce fruits at an early stage.

Taking into account that the total area occupied by the crop was 7.2 m2  a density of 10 plants m− 2 was estimated, so that the productions obtained for the different blocks of 6 plants were between 140 and 565 g m− 2 . The quality variables  and SPAD values were only affected by the elapsed time since transplanting . Overall, SPAD values tended to be higher at the end of the period, with a more marked trend and lower average values in new leaves when compared with old leaves . On the other hand, the effect of the differences between the two substrate types studied on productive variables  varied along the growing period studied as revealed by the significant interaction between this factor and time. The number of flower buds and the number of flowers were initially higher for the plants cultivated with bare roots than with rockwool, but at the end of the trial both values were increased for the plants in rockwool . On the contrary, the number of fruits with bare roots was slightly lower at the beginning, but at the end of the trial it showed the highest values, whereas the accumulated weight of fruits that was initially lower for bare roots eventuallyequalled those corresponding to rockwool at the end of the period . Our systems allowed to maintain stable water conditions throughout the time period of the test, resorting to simple pH control operations by adding alkalis, supplementing the deficit nutrients for the plants of these systems in the form of EDDHA, potassium sulphate, and sodium and calcium hydroxides; and reduction of nitrate levels based on water changes. The total time devoted to these tasks did not significantly increase the time normally required for operations related to the hydroponic cultivation of strawberries, where the pH and levels of nutrients in the nutritive solution must also be controlled and regulated. In this sense, pH regulation is a fundamental operation to optimize the extraction of nutrients by the roots of plants, the development and growth of fish and the performance of the bacterial community in the biofilters. This can be attributed to the use of a low fish density in our aquaponic facilities, which allowed the use of a simple system of aquaculture circuits . This avoids the need for a clarifier and settler, ebb and flow bench while the simple biological filters used reduced the investment since there is no requirement of extra aeration devices or powerful pumps for recirculation of water. However, if the density of fish was to be increased or the duration of the test prolonged, it is likely that these common elements in RAS facilities would have to be introduced.

The initial adjustment that was made of the ratio between the area dedicated to strawberry cultivation and the daily amount of feed provided to the fish was not fully appropriate, probably due to the fact that most of the bibliographic references used for the initial adjustment were based on the use of tilapia, a fish species that requires lower protein contents in the compound feed supplied. Tench requires higher levels of crude protein, so the total contribution of nitrates generated was somewhat higher in our systems. This explains the substantial increase in the daily rate of water replacement from day 49 to keep nitrate levels stable around 70 mg L− 1 . Despite this increase in water consumption, the final daily water replacement rate was around 2.2%, well below the 5–10% required in recirculating aquaculture systems. Regarding this water saving potential, in an aquaponic tench-lettuce production system similar to this one, the authors obtained daily water replacement rates of 1.18% in a 65 days period . This should be highlighted, since in the conditions in which strawberry productions are carried out in Spain, water is a scarce resource. In this sense, the results obtained by Van Ginkel et al.  comparing traditional agricultural productions in California with hydroponic and aquaponic productions, pointed out that these systems are recommendable strategies to save water, since consumption was 66 and 8 times lower than in the traditional systems, respectively. As previously mentioned, the growth of the animals in the three tanks was quite homogeneous, although the weight increases were not of great magnitude, something that is characteristic of this species. The survival rate of animals was very high , within the range described by other authors  for animals with similar weights .This confirms the high adaptability of this species to the aquaponics system. In order to keep the water quality parameters stable over time, regardless of the changing weight of the fish with time elapsed, it is recommended to use several connected fish tanks . In each of these tanks there would be fish of different ages, which would be harvested in stages, thus maintaining a similar proportion of animals in different growth stages. With this system, fingerlings should be restocked each time a tank is harvested . This arrangement of tanks would also allow increasing the density of fish in a simple way, improving the productivity associated with fish farming. In view of the current findings, the slow growth of the tench is verified, which supposes an important obstacle for the extension of its cultivation in recirculating aquaculture systems, except to support sport fishing favouring the repopulation of the water courses in which naturally it is found.