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Understanding Fate of PPCPS in Soil-Plant Systems Irrigated with Treated Wastewater

Gan, Jianying
University of California - Riverside
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We propose to study the bioaccumulation of pharmaceutical and personal care products (PPCPs) by common vegetables and strawberries that are irrigated exclusively with treated wastewater. Our focus will be on the accumulation of PPCPs into the edible products that are typically consumed raw, the processes in soil that may potentially affect this uptake and off-site movement such as leaching.

The proposed research contributes to the long-term sustanability of U.S. agriculture by exploring the use of treated wastewater as an optional source of irrigation water and by considering the food safety issues as a result of this practice. This project will provide baseline information on the uptake and accumulation of PPCPs in vegetables and fruits (strawberry) that are irrigated with treated wastewater.

Specifically, we will:

  1. Carry out field studies at two locations to irrigate strawberries and 7 common vegetables with non-spiked treated wastewater and evaluate the occurrence of PPCPs in raw edible tissues at maturity;
  2. Carry out hydroponic experiments to trace plant uptake, translocation, and accumulation of 14C-PPCPs and characterize metabolism and composition of residues;
  3. Conduct soil incubation experiments using 14C-PPCPs to evaluate mineralization, metabolism, and formation of bound residues and relate behaviors of PPCPs in soil to availability of PPCPs for plant uptake;
  4. Couple batch parameter measurements, analysis of PPCP distribution in field soil profiles, and numerical simulation to evaluate leaching risks of PPCPs in agricultural fields receiving treated wastewater for irrigation.
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Non-Technical Summary: In arid and semi-arid regions (e.g., American Southwest), municipal treated wastewater may become an important water source to augment agricultural irrigation, thus enhancing the long-term sustainability of agriculture that is currently impacted by water scarcity due to urbanization, droughts, and climate changes. An emerging threshold issue to this reuse, however, is the potential transfer and accumulation of trace contaminants such as pharmaceutical and personal products (PPCPs) from the recycled water to edible plant tissues. At present, our collective knowledge on this topic is essentially blank. We propose to evaluate the bioaccumulation of PPCPs by common vegetables and strawberry that are irrigated exclusively with treated wastewater. We will carry out greenhouse hydroponic experiments to characterize the uptake and translocation of PPCPs by using 14C-labeled compounds, and quantify levels of PPCPs in the edible tissues of lettuce, cabbage, bell pepper, tomato, carrot, parsley, radish, and strawberry in field plots irrigated solely with treated wastewater. In addition, we will nvestigate fate processes in soil that affect the availability of PPCPs for plant uptake, and evaluate the leaching risk of PPCPs through field monitoring and numerical simulation. This project will provide the much needed baseline information on the potential occurrence of PPCPs in fresh produces from reuse of wastewater. The study findings will be of great value to future efforts for understanding the human toxicological significance of potential PPCP occurrence in food sources, and for developing options that promote the safe use of treated wastewater in agriculture.

Approach: A) Plant Uptake of 14C-PPCPs in Hydroponic Systems: During the early phase of this project, we will conduct hydroponic experiments in greenhouses using four 14C-labeled PPCPs, i.e., 14C-naproxen, 14C-acetaminophen, 14Cerythromycin,and 14C-bisphenol A. These experiments will provide information on the uptake and translocation potential of the select PPCPs, as well as the distribution and forms (i.e., conjugated vs. extractable) of their residues in plant tissues. Comparisons of plant uptake between species will also be examined. B)Plant Uptake of PPCPs under Field Conditions: Late in the second year to midway through the third year of this project, in collaboration with county farm advisors, we will irrigate plants grown in field plots with non-spiked, i.e., acutal tertiary treated wastewater and analyze for accumulation of PPCPs in the edible parts at harvest. The irrigation, fertilization, and other practices will closely follow those that are conventionally used in the industry. Two locations in southern and coastal California will be used, and both are in areas of heavy production of strawberries and various vegetable crops. We will collaborate with water resources advisor Dr. Darren Haver to carry out the experiment at the UC South Coast Research and Extension Center (SCREC) in Orange County, CA, and with strawberry and vegetable crops farm advisor Dr. Oleg Daugovish for the experiment at the UC Hansen Agricultural Center in Ventura County, CA. By using research field sites, we will have complete flexibility and accessibility (e.g. setting up or modification of irrigation systems, irrigation with treated wastewater), as well as free dissemination of research results to the scientific community and the public. C) Fate and Transport of PPCPs in Soil: Processes such as sorption and degradation in soil affect the availability of PPCPs for plant uptake, and off-site transport, such as leaching, may present another risk in the use of treated wastewater for agricultural irrigation. In this project, fate and transport of PPCPs in soil will be evaluated through four ways: 1) a laboratory incubation experiment with 14C-PPCPs; 2) laboratory batch experiments to determine partition coefficient Kd and half-lives (T1/2) for target PPCPs; 3) analysis of soil cores to characterize soil distribution of PPCPs after irrigation of treated wastewater in field plots; and 4) model simulation to evaluate leaching potential of PPCPs under different irrigation conditions. The lab-derived information will be used to interpret field observations, and as model inputs in numerical simulation to predict PPCP transport in soil and accumulation in plants.

Funding Source
Nat'l. Inst. of Food and Agriculture
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Predictive Microbiology
Sanitation and Quality Standards
Natural Toxins
Viruses and Prions
Bacterial Pathogens
Chemical Contaminants