Journal of Environmental Quality

Neonicotinoid pesticides can persist in soils for extended time periods; however, they also have a high potential to contaminate ground and surface waters. Studies have reported negative effects associated with neonicotinoids and nontarget taxa, including aquatic invertebrates, pollinating insect species, and insectivorous birds. This study evaluated factors associated with clothianidin (CTN) degradation and sorption in Missouri wetland soils to assess the potential for wetland soils to mitigate potential environmental risks associated with neonicotinoids. Solid-to-solution partition coefficients (K-d) for CTN sorption to eight wetland soils were determined via single-point sorption experiments, and sorption isotherm experiments were conducted using the two most contrasting soils. Clothianidin degradation was determined under oxic and anoxic conditions over 60 d. Degradation data were fit to zero- and first-order kinetic decay models to determine CTN half-life (t(0.5)). Sorption results indicated CTN sorption to wetland soil was relatively weak (average K-d, 3.58 L kg(-1)); thus, CTN has the potential to be mobile and bioavailable within wetland soils. However, incubation results showed anoxic conditions significantly increased CTN degradation rates in wetland soils (anoxic average t(0.5), 27.2 d; oxic average t(0.5), 149.1 d). A significant negative correlation was observed between anoxic half-life values and soil organic C content (r(2) = .782; p = .046). Greater CTN degradation rates in wetland soils under anoxic conditions suggest that managing wetlands to facilitate anoxic conditions could mitigate CTN presence in the environment and reduce exposure to nontarget organisms. Missouri Department of Conservation; USDA-NIFAUnited States Department of Agriculture (USDA) [MO-HANR0007]; Multi-State Working Group [W3045 (MO-MSNR0002)]; MDC; University of Missouri; U.S. Fish and Wildlife ServiceUS Fish & Wildlife Service; USGSUnited States Geological Survey; Wildlife Management Institute Funding for this research was provided through a cooperative agreement with the Missouri Department of Conservation. Partial support was also provided by USDA-NIFA through Hatch funding (MO-HANR0007) and Multi-State Working Group W3045 (MO-MSNR0002). The authors thank the following individuals for their contributions: Craig Scroggins of MDC; Elizabeth Spiegel, Edward Winchester, and Kathleen Hatch from the USDA-ARS; and Elizabeth Tustison, Laura Satkowski, Rachel Owen, and Anson Main of the University of Missouri. The Missouri Cooperative Fish and Wildlife Research Unit is jointly sponsored by MDC, the University of Missouri, the U.S. Fish and Wildlife Service, the USGS and the Wildlife Management Institute. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Public domain – authored by a U.S. government employee