Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2011
Publication Date: 3/1/2011
Citation: Kroger, R., Moore, M.T. 2011. Chemical residence time and hydrological conditions influence fipronil reduction in vegetated aquatic mesocosms. Journal of Environmental Quality. 40:559-565. Interpretive Summary: Pesticides applied to agricultural fields may be washed off due to irrigation or storm events. Vegetated ditches and constructed wetlands have been suggested as efficient management practices to help reduce impacts of pesticide runoff. The current study demonstrated that by increasing the amount of contact time the pesticide has with plants, we can reduce the amount of pesticides entering rivers, lakes, and streams. This research plays a significant role in establishing future management practices for agricultural non-point source runoff.
Technical Abstract: Fipronil, a phenyl-pyrazole insecticide and its metabolites (Fipronil sulfone, sulfide and desulfinyl) is often used in rice production agriculture with elevated runoff concentrations and loads having potential toxicological effects on downstream aquatic environments. This study evaluated two species of aquatic plants (Typha latifolia L. and Thalia dealbata Fraser ex Roscoe) placed in series against a non-vegetated control in reducing fipronil and associated metabolite concentrations and loads. Chemical residence time and hydrological condition (inundated vs. dry) were treatment effects used for comparison. The vegetated mesocosms significantly reduced higher loads and concentrations of fipronil, fipronil sulfone and sulfide in both inundated and dry hydrological conditions. The inundated condition reduced greater than 50% of influent fipronil concentrations and between 60-70% of fipronil loads, significantly higher than the dry condition (10-32% concentration and load). Results suggest that innovative management strategies in aquatic systems associated with agriculture that increase chemical or water residence time as well as maintain a diverse vegetation assemblage will significantly improve pesticide concentration and load reductions to sensitive downstream aquatic ecosystems.