Plant uptake of contaminants of emerging concern in agroecosystems irrigated with reclaimed water

This research investigates chemical (antibiotics) and microbiological (antibiotic resistance) concerns related to the use of reclaimed water in traditional (soil-based) and non-traditional (hydroponics) farming applications. The long-term goal of this research is to clarify if irrigation with reclaimed water contributes to environmental and human exposure to chemical and microbiological contaminants of emerging concern (CECs), with a specific emphasis on antibiotics and antibiotic resistance. The research will also assess how the associated risks can be mitigated with advanced pretreatment (i.e., ultrafiltration and ozonation) of the reclaimed water. This work will evaluate factors such as plant species, irrigation methods, and conventional vs. advanced pretreatment of reclaimed water on plant uptake of CECs. The derived endpoints and measured concentrations will be used to predict potential human exposures and ecological implications, and the results can further be used by management agencies (e.g., USDA, EPA, and USGS) for environmental risk assessments. Specific objectives include the following:To evaluate the accumulation of CECs in edible plants irrigated with reclaimed water.To evaluate the persistence and transport of CECs during irrigation with reclaimed water.To evaluate changes in the microbial community and the occurrence of antibiotic resistance (ARBs and ARGs) during irrigation with reclaimed water.To educate undergraduate- to doctoral-level students in research areas related to water quality, agricultural engineering, and environmental science.This research will evaluate the influence of plant species, water application rates, planting methods/irrigation strategies, and pretreatment of reclaimed water on plant accumulation of CECs. Specifically, the research will compare more traditional soil-based agriculture against emerging hydroculture applications. In addition, the research will evaluate whether advanced pretreatment of the reclaimed water with ozonation yields significant benefits by reducing CEC loadings to plants. To guide the objectives of the proposal, the following testable hypotheses (H) are formulated to answer the corresponding research questions (Q):Q1) Do plants have different capacities to uptake and accumulate CECs, and does accumulation vary within different structures of the plants?H1) If plant uptake of CECs is dependent on plant species (i.e., leafy vs. fruit plants) and structures (roots vs. shoots vs. fruits), then CECs will occur at different levels in different plant species and different structures of each plant.Q2) Is plant uptake of CECs a compound- and concentration-dependent process (e.g., as a function of the CEC and water source/pretreatment)?H2) If plant uptake of CECs is related to the CEC and its initial concentration, then the accumulation of CECs in plant tissues will differ depending on the CEC and its concentration in irrigation water.Q3) Does CEC accumulation differ when plants are grown in traditional soil-based systems vs. hydroponics-based environments?H3) If different planting strategies (e.g., soil vs. hydroponics) influence plant uptake of CECs through differences in water delivery, then the accumulation of CECs will differ in plants harvested from these systems.Q4) Does CEC persistence in soils irrigated with reclaimed water differ based on plant species, irrigation strategy, or water source/pretreatment?H4) If reclaimed water is a source of CECs in soil and persistence is a function of irrigation practice and plant species, then CECs will be found in the soils after plant harvest at different concentrations.Q5) Does irrigation practice and/or plant species impact microbial community structure and the prevalence of antibiotic resistance in the system?H5) If the microbial community varies depending on plant species, water matrix (i.e., differing level of pretreatment), and/or irrigation strategy (soil-based vs. hydroponics-based), then the structure of the microbial community and the prevalence of ARBs and ARGs will differ in each system.