In comparison with pesticides, only sporadic research has shown detoxification of PPCPs by POD and GST in plants. In the present study, activities of POD and GST increased in a dose-dependent manner in both roots and leaves after exposure to PPCPs . This observation was consistent with Bartha et al. and Huber et al. , who observed oxidation of diclofenac by plant peroxidases, and also glutathione conjugation in Typha latifolia. These mechanistic studies, together with our results, clearly show that the POD and GST enzyme families may play an important role in transformation and conjugation of PPCPs in plants. Glutathione is one of the major soluble low molecular weight antioxidants, and also the major non-protein thiol in plant cells , contributing to maintain the cellular redox homeostasis and signaling. Moreover, conjugation with xenobiotics by GSH may be a common pathway for plant metabolism of various man-made chemicals . Glutathione conjugation with diclofenac , 8:2 fluorotelomer alcohol and chlortetracycline have been previously observed in plants. It is well known that these processes require extensive utilization of reduced GSH as an electron donor and subsequently produce oxidized glutathione . The changes in the cellular glutathione pool, specially the associated ratio of reduced to oxidized glutathione, play a central role in plant defense responses . Glutathione homeostasis after exposure to trace levels of PPCPs, however,growing hydroponically has not been well documented so far. In this study, the glutathione content increased at low PPCP doses, while decreased to normal levels at the highest PPCP treatment level . The GSSG content was unchanged when the PPCP concentrations were low , but showed a significant increase when the PPCP concentration was increased to 50 mg L! 1 . The depletion observed in cellular GSH could contribute to the PPCP-induced oxidative stress and detoxification of xenobiotics.
Meanwhile, the different responses of GSH in root and leaves indicated that roots may be the main site to express PPCP toxicity and induce PPCP detoxification. Given the dominance of GSH conjugates as observed for pesticides, it is possible that trace contaminants such as PPCPs may be removed similarly by GSH conjugation. It is therefore imperative to conduct further research to explore the mechanisms and pathways of PPCP phytotransformation by GSTs after uptake by plants.On the whole, the present study provided evidence that some PPCPs may be translocated systemically, and ultimately posed toxicity effects in higher plants. Oxidative stress response may reflect the intensity of PPCP treatment and sensitivity of plant species to PPCPs, and may be used as indicators for early plant response to trace organics introduced into agroecosystems. Furthermore, plants may detoxify PPCPs through different mechanisms, including enhanced antioxidant defense systems to prevent oxidative damage and increased activities of xenobioticmetabolizing enzymes. These mechanisms help maintain plant physiological, biochemical and molecular functional integrity, offering the possibility to use some of these endpoints as biomarkers for predicting phytotoxicity induced by PPCPs and likely other man-made chemicals. Further research is needed to evaluate the physiological and biological responses of plants in realistic field practices, such as irrigation with treated wastewater or fertilization with biosolids and animal wastes in agriculture.The Paharpur Business Centre and Software Technology Incubator Park is a 7 story, 50,400 ft2 office building located near Nehru Place in New Delhi India. The occupancy of the building at full normal operations is about 500 people. The building management philosophy embodies innovation in energy efficiency while providing full service and a comfortable, safe, healthy environment to the occupants. Provision of excellent Indoor Air Quality is an expressed goal of the facility, and the management has gone to great lengths to achieve it. This is particularly challenging in New Delhi, where ambient urban pollution levels rank among the worst on the planet.
The approach to provide good IAQ in the building includes a range of technical elements: air washing and filtration of ventilation intake air from rooftop air handler, the use of an enclosed rooftop greenhouse with a high density of potted plants as a bio-filtration system, dedicated secondary HVAC/air handling units on each floor with re-circulating high efficiency filtration and UVC treatment of the heat exchanger coils, additional potted plants for bio-filtration on each floor, and a final exhaust via the restrooms located at each floor. The conditioned building exhaust air is passed through an energy recovery wheel and chemisorbent cartridge, transferring some heat to the incoming air to increase the HVAC energy efficiency. Flooring is a combination of stone, tile and “zero VOC” carpeting. Wood trim and finish appears to be primarily of solid sawn materials, with very little evidence of composite wood products. Furniture is likewise in large proportion constructed from solid wood materials. The overall impression is that of a very clean and well-kept facility. Surfaces are polished to a high sheen, probably with wax products. There was an odor of urinal cake in the restrooms. Smoking is not allowed in the building. The plants used in the rooftop greenhouse and on the floors were made up of a number of species selected for the following functions: daytime metabolic carbon dioxide absorption, nighttime metabolic CO2 absorption, and volatile organic compound and inorganic gas absorption/removal for air cleaning. The building contains a reported 910 indoor plants. Daytime metabolic species reported by the PBC include Areca Palm, Oxycardium, Rubber Plant, and Ficus alii totaling 188 plants . The single nighttime metabolic species is the Sansevieria with a total of 28 plants . The “air cleaning” plant species reported by the PBC include the Money Plant, Aglaonema, Dracaena Warneckii, Bamboo Palm, and Raphis Palm with a total of 694 plants .
The plants in the greenhouse numbering 161 of those in the building are grown hydroponically, with the room air blown by fan across the plant root zones. The plants on the building floors are grown in pots and are located on floors 1-6. We conducted a one-day monitoring session in the PBC on January 1, 2010. The date of the study was based on availability of the measurement equipment that the researchers had shipped from Lawrence Berkeley National Lab in the U.S.A. The study date was not optimal because a large proportion of the regular building occupants were not present being New Year’s Day. An estimated 40 people were present in the building all day during January 1. This being said, the building systems were in normal operations, including the air handlers and other HVAC components. The study was focused primarily on measurements in the Greenhouse and 3rd and 5th floor environments as well as rooftop outdoors. Measurements included a set of volatile organic compounds and aldehydes, with a more limited set of observations of indoor and outdoor particulate and carbon dioxide concentrations. Continuous measurements of Temperature and relative humidity were made selected indoor and outdoor locations. Air sampling stations were set up in the Greenhouse, Room 510, Room 311, the 5th and 3rd floor air handler intakes,growing strawberries hydroponically the building rooftop HVAC exhaust, and an ambient location on the roof near the HVAC intake. VOC and aldehyde samples were collected at least once at all of these locations. Both supply and return registers were sampled in rooms 510 and 311. As were a greenhouse inlet register from the air washer and outlet register ducted to the building’s floor level. Air samples for VOCs were collected and analyzed following the U.S. Environmental Protection Agency Method TO-17 . Integrated air samples with a total volume of approximately 2 L were collected at the sites, at a flow rate of <70 cc/min onto preconditioned multibed sorbent tubes containing Tenax-TA backed with a section of Carbosieve. The VOCs were desorbed and analyzed by thermodesorption into a cooled injection system and resolved by gas chromatography. The target chemicals, listed in Table 1, were qualitatively identified on the basis of the mass spectral library search, followed by comparison to reference standards. Target chemicals were quantified using multi-point calibrations developed with pure standards and referenced to an internal standard. Sampling was conducted using Masterflex L/S HV-07553-80 peristaltic pumps assembled with quad Masterflex L/S Standard HV-07017-20 pump heads. Concentrations of formaldehyde, acetaldehyde, and acetone were determined following U.S. Environmental Protection Agency Method TO-11a . Integrated samples were collected by drawing air through silica gel cartridges coated with 2,4-dinitrophenylhydrazine at a flow rate of 1 Lpm. Samples utilized an ozone scrubber cartridge installed upstream from the sample cartridge. Sample cartridges were eluted with 2 mL of high purity acetonitrile and analyzed by high-performance liquid chromatography with UV detection and quantified with a multi-point calibration for each derivitized target aldehyde. Sampling was conducted using Masterflex L/S HV-07553-71 peristaltic pumps assembled with dual Masterflex L/S Standard HV-07016-20 pump heads. Continuous measurements of PM2.5 using TSI Dustrak model 8520 monitors were made in Room 510 and at the rooftop-sampling site from about 13:30 to 16:30 of the sampling day. The indoor particle monitor was located on a desk in room 510 and the outdoor monitor was located on a surface elevated above the roof deck. Carbon dioxide spot measurements of about 10-minute duration were made throughout the building during the afternoon using a portable data logging real-time infrared monitor . Temperature and RH were monitored in the Greenhouse, room 510 and room 311 using Onset model HOBO U12-011 data loggers at one-minute recording rates. Outdoor T and RH were not monitored. The measured VOC concentrations as well as their limits of quantitation by the measurement methods are shown in Table 2. Figures 1-6 show bar graphs of these VOCs. Unless otherwise shown, all measured compounds were above the minimum detection level, but not all measurements were above the LOQ.
Those measurements with concentrations below the LOQ should be considered approximations. These air contaminants are organized by possible source categories including: carbonyl compounds that can be odorous or irritating; compounds that are often emitted by building cleaning products; those associated with bathroom products; those often found emitted from office products, supplies, materials, occupants, and in ambient air; those found from plant and wood materials as well as some cleaning products; and finally plasticizers commonly emitted from vinyl and other flexible or resilient plastic products. The groupings in this table are for convenience; many of the listed compounds have multiple sources so the attribution provided may be erroneous. The carbonyl compounds include formaldehyde that can be emitted from composite wood materials, adhesives, and indoor chemical reactions; acetaldehyde from building materials and indoor chemistry; acetone from cleaners and other solvents. Benzaldehyde sources can include plastics, dyes, fruits, and perfumes. Hexanal, nonanal, and octanal can be emitted from engineered wood products. For many of these compounds, outdoor air can also be a major source. Formaldehyde and acetone were the most abundant carbonyl compounds observed in the PBC. For context, the California 8-h and chronic non-cancer reference exposure level for formaldehyde is 9 µg m-3 and the acute REL is 55 µg m-3 . The 60 minute average formaldehyde concentrations observed in the PBC exceeded the REL by up to a factor of three. Acetone has low toxicity and the observed levels were orders of magnitude lower than concentrations of health concern. Hexanal, nonanal, and octanal are odorous compounds at low concentrations; odor thresholds established for them are 0.33 ppb, 0.53 ppb, and 0.17 ppb, respectively . Average concentrations observed within the PBC building were 3.8±0.8 ppb, 3.5±0.6 ppb, and 1.4±0.2 ppb, for these compounds, respectively, roughly ten times higher than the odor thresholds. Concentrations of these compounds in the supply air from the greenhouse were substantially lower, although stillin excess of the odor thresholds. The concentration of hexanal and nonanal roughly doubled the ambient concentrations as the outside air passed through the greenhouse. Octanal concentrations were roughly similar in the ambient air and in the air exiting the greenhouse. Concentrations of benzene, d-limonene, n-hexane, naphthalene and toluene all increased in the greenhouse air in either the AM or PM measurements. The measured levels of these compounds were far below any health relevant standards, although naphthalene concentrations reached close to 50% of the California REL of 9 µg m-3 . The concentrations of these compounds were generally somewhat higher indoors relative to the greenhouse concentrations.