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In this proposed project, we will test our hypothesis that reclaimed-water-borne chemicals of emerging concern (CECs) can bioaccumulate to measurable levels into edible food crops. We believe this bioaccumulation will be strongly dependent on not only the specific identity and properties of the CECs, but also on the soil chemistry and plant physiology. More specifically, we believe simplistic bioaccumulation models will work well for the relatively hydrophobic CECs commonly present in reclaimed water, but these models will require modification to enable evaluation of ionogenic CECs that do not fit within the traditional organic chemical partitioning paradigms. The ultimate goal of the proposed research is to assess the factors controlling the bioaccumulation of CECs from reclaimed water into food crops and, in doing so, validate or modify existing models used to predict plant accumulation. <P>Our specific research objectives are: <P>Objective 1: Evaluate the dose-dependent bioaccumulation of selected CECs into edible food crops under controlled water reuse conditions. <P>Objective 2: Determine the effects of cumulative water reuse loading rates and typical soil geochemical conditions on CEC bioaccumulation. <P>Objective 3: Examine the applicability of existing models and, if necessary, modify existing models to describe CEC bioaccumulation in plants. <P>Objective 4: Validate the results from greenhouse and modeling studies through limited field monitoring and experimental studies.<P> Objective 5: Evaluate the results of these studies within the context of human exposure to CECs through the consumption of contaminated food crops. <P>The significance of the overall research program is that it will: <ul> <LI> Identify the key CECs present in reclaimed water that may pose the greatest risk for bioaccumulation in edible plants under conditions representing common water reuse practices. <LI>Determine the role of site-specific conditions (i.e., soil type) and management practices (i.e., hydraulic loading rates, crop selection) leading to minimal chemical bioaccumulation from reclaimed water.<LI>Determine the appropriateness and limitations of existing modeling approaches for predicting CEC bioaccumulation in plants. <LI>Direct future development of management practices for the use of reclaimed water in food crop irrigation.
</ul>Findings from this study will point to broad considerations for minimizing unintentional exposure of the general public to organic chemicals that may bioaccumulate from reclaimed water into edible food crops. As a result, management strategies and site-specific factors leading to decreased CEC bioaccumulation potential will be identified. Furthermore, through the examination and possible modification of existing bioaccumulation models, this project will enable scientists and practitioners to more rapidly evaluate the potential risks associated with the use of reclaimed water in the irrigation of edible food crops.
Non-Technical Summary: This proposed project will evaluate the potential for bioaccumulation of contaminants of emerging concern (CECs) from reclaimed water into food crops. In particular, the bioaccumulation of CECs such as pharmaceuticals, personal care products, and perfluorochemicals into plants will be assessed in a series of field and laboratory-based studies. A field study will be conducted at an agricultural site that has been using reclaimed water for food crop irrigation for several decades. The concentrations of CECs in the crops, soil, and the reclaimed water will be measured and compared to a control site irrigated with well water. The dose-dependent bioaccumulation of CECs will also be assessed in laboratory-based studies with reclaimed water fortified with CECs. Subsequent studies will examine the effect of soil organic matter and cumulative use of reclaimed water. To ensure comparability of results, at least two of the specific plant species grown in the greenhouse studies will be identical to those used in the field. The validity of existing models for predicting CEC accumulation will be assessed, and potential improvements identified. To further validate the results of the laboratory studies, controlled field studies will be conducted over two growing seasons using crops, soil, and reclaimed water similar to that used in the greenhouse studies. Finally, results will be placed within the context of human exposure to CECs through comparisons to the acceptable daily intake values. The end result of this study will be an in-depth evaluation of the potential bioaccumulation of CECs into food crops from reclaimed water. <P> Approach: The potential for bioaccumulation of CECs present in reclaimed water will be investigated in controlled laboratory and experimental field studies as well as field monitoring studies. Modeling efforts will aid in the extrapolation of results from the laboratory to the field, and will ensure broader applicability of the results of this proposed research effort. The objectives of this study, as detailed above, will be met through the completion of the following six tasks: Task 1: Validate analytical protocols for accurate and reliable measurement of the targeted CECs in the appropriate matrices (i.e., reclaimed water, soil, edible plant materials) Task 2: Conduct field-scale monitoring of edible food crops irrigated with reclaimed water at sites where reclaimed water has been applied for many years. Task 3: Determine the relationship between CEC levels in reclaimed water and uptake into food crops commonly eaten fresh (including lettuce, tomatoes, strawberries, and carrots; Task 3a) and examine the role of soil type, geochemical parameters, and the cumulative effects of the use of reclaimed water on CEC bioaccumulation in food crops irrigated with reclaimed water (Task 3b). Task 4: Evaluate and, if necessary, modify existing plant bioaccumulation models to enable prediction of CEC bioaccumulation from reclaimed water into plants. Task 5: Conduct controlled field experiments on a limited scale to validate CEC bioaccumulation models and confirm validity of field-scale monitoring results. Task 6: Evaluate findings in the context of human exposures to CECs and disseminate results to the agricultural water reuse community and the broader public.