Grantee Research Project Results
2018 Progress Report: Reclaimed Water Irrigation: Plant Accumulation and Risks of Contaminants of Emerging Concern (CECs)
EPA Grant Number: R835829Title: Reclaimed Water Irrigation: Plant Accumulation and Risks of Contaminants of Emerging Concern (CECs)
Investigators: Gan, Jay , Trumble, John T.
Current Investigators: Gan, Jay , Trumble, John T. , Dudley, Stacia , Pennington, Marcus , sun, Chengliang
Institution: University of California - Riverside
EPA Project Officer: Packard, Benjamin H
Project Period: September 1, 2015 through August 31, 2018 (Extended to February 28, 2020)
Project Period Covered by this Report: September 1, 2017 through August 31,2018
Project Amount: $749,631
RFA: Human and Ecological Health Impacts Associated with Water Reuse and Conservation Practices (2014) RFA Text | Recipients Lists
Research Category: Water , Human Health
Objective:
In arid and semi-arid regions such as the southwestern U.S., municipally treated wastewater (or reclaimed water) is potentially a valuable water resource that may be used for augmenting agricultural irrigation, thus alleviating water scarcity caused by urbanization and droughts. A hurdle to this beneficial reuse, however, is the perceived uptake of and risks from contaminants of emerging concern (CECs) from the treated wastewater via food crops. In this project, we aim to identify CECs with the highest potential for plant accumulation, obtain first-hand values of occurrence of CECs in edible products of common vegetables and other food crops, and further characterize acute and sublethal effects of selected CECs on a range of important insects. This project will provide the much-needed first-hand information on the occurrence and potential risks of CECs in food plants when treated wastewater is used for irrigation. The study findings will be of great value to the scientific community and the society-at-large for developing knowledge that promotes the safe reuse of treated wastewater.
Progress Summary:
Our project has continued to make significant progress. The progress is summarized below.
Plant Uptake and Metabolism of CECs:
We have carried out studies to explore metabolism of pharmaceuticals in plants using Arabidopsis thaliana cells and common vegetables (i.e., radish, cucumber, lettuce, and carrots).
For most CECs considered so far, we have observed active metabolism including rapid and extensive conjugation with amino acids, sulfates, and glucose. These findings suggest that conjugation is a common pathway for plants to transform pharmaceuticals and such conjugation may act to preserve the bioactivity of these compounds if they are deconjugated through enzymatic reactions in, e.g., human gut. The biological activity of these transformation products should be determined to understand their potential risks to non-target organisms including humans.
Stress-related Symptoms Induced by CECs and Detoxification Mechanisms:
Introduction of CECs into soil through water reuse may also cause stresses to plants and hence phytotoxicity. Using cucumber as a model plant, we have evaluated the phytotoxicity of a mixture of pharmaceuticals and personal care products (PPCPs). Results show that PPCPs induced oxidative damage to the plasma membrane and lipid in plant seedlings, and the damage was also proportional to the exposure concentration. The levels of chlorophyll a and b decreased with increasing PPCP concentrations. The results together demonstrate that contact with PPCPs can cause a range of reactions in higher plants and that at high concentrations, physiological and biochemical processes may be altered and compromised. Further, using acetaminophen as a model PPCP we have explored the roles of glutathione conjugation in biotransformations and detoxification of PPCPs in vegetables. Results show that acetaminophen was taken up by plants, and conjugated quickly with glutathione (GSH). The GSH-conjugates accumulated in roots were immobile. Enzymes involved in GSH synthesis, regeneration and transport were consistently induced to maintain the GSH homeostasis. These results highlight the role of glutathione in mitigating plant exposure to such emerging contaminants.
Effects of PPCPs on Terrestrial Invertebrates:
We have continued our work to investigate acute and developmental toxicity effects of CECs on agriculturally and economically important insects, including Megaselia scalaris, Trichoplusia ni, and Myzus persicae. An vital detritivore, Megaselia scalaris (the coffin fly), was treated with environmentally relevant concentrations of select PPCPs. Caffeine was found to increase the mortality in the flies. Of the individuals that reached adulthood, those that were treated with antibiotics or hormones were delayed in development when compared to the control. Interestingly, PPCP treatment had an impact on sex differences and on when the sexes emerged. There was an increased time in the larval stage in the antibiotic and hormone-treated insects, and females took significantly longer to become pupa in hormone-treated groups when compared to the control.
In another study, important agriculture pests, the cabbage looper (Trichoplusia ni), and green-peach aphids (Myzus persicae) were treated with environmentally relevant concentrations of select PPCPs through a plant matrix. For cabbage loopers, antibiotics were found to increase mortality through the tomato plant matrix, and antibiotic, hormone and mixture treatments displayed the greatest effect on the T.ni’s microbial community. Aphids and their microbiome were found to be relatively unaffected by all of the PPCPs, but their host plant (bell peppers, Capsicum annum) displayed an overall decrease in plant size in antibiotic and mixture treated plants.
Earthworms (Eisenia fetida) exposed to four CECs, naproxen, diazepam, sulfamethoxazole and methylparaben, at environmentally relevant concentrations displayed a potential for uptake and metabolism of all four compounds with the major metabolite of sulfamethoxazole, N4-acetylsulfamethoxazole, being the most abundant metabolite in earthworm tissues at the end of the experiment. Exposure to these CECs also resulted in an upregulation of enzymes associated with oxidative stress, indicating that CECs may cause molecular toxicity to earthworms. Therefore, exposure to CECs at environmentally relevant concentrations may cause a range of effects, ecologically or agriculturally important insects.
Future Activities:
We currently are completing a field study where we are evaluating the accumulation of PPCPs from biosolids by common fruit trees under field conditions. We will use the remaining time to complete the field study, analyze data, and develop manuscripts for publication in scientific journals, as well as materials for outreach/education.
References:
Journal Articles on this Report : 4 Displayed | Download in RIS Format
Other project views: | All 23 publications | 16 publications in selected types | All 16 journal articles |
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Type | Citation | ||
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Dudley S, Sun C, Jiang J, Gan J. Metabolism of sulfamethoxazole in Arabidopsis thaliana cells and cucumber seedlings. Environmental Pollution 2018;242(Pt B):1748-1757. |
R835829 (2018) R835829 (2019) |
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Fu Q, Dudley S, Sun C, Schlenk D, Gan J. Stable isotope labeling-assisted metabolite probing for emerging contaminants in plants. Analytical Chemistry 2018;90(18):11040-11047. |
R835829 (2018) R835829 (2019) |
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Sun C, Dudley S, McGinnis M, Gan J. Hydrogen peroxide mediates triclosan-induced inhibition of root growth in wheat seedlings. Environmental Pollution 2018;243(Pt A):472-479. |
R835829 (2018) R835829 (2019) |
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Sun C, Dudley S, McGinnis M, Gan J. Acetaminophen detoxification in cucumber plants via induction of glutathione S-transferases. Science of the Total Environment 2018;646:431-439. |
R835829 (2018) R835829 (2019) |
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Supplemental Keywords:
Water reuse, emerging contaminants, environmental sustainability, PPCPs.Relevant Websites:
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.