Clothianidin decomposition in Missouri wetland soils

Authors: BERINGER, C - University Of Missouri; GOYNE, K - Virginia Polytechnic Institution & State University; Lerch, Robert; WEBB, E - Us Geological Survey (USGS); MENGEL, D - Missouri Department Of Conservation

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/30/2020
Publication Date: 1/18/2021
Citation: Beringer, C.J., Goyne, K.W., Lerch, R.N., Webb, E.B., Mengel, D. 2021. Clothianidin decomposition in Missouri wetland soils. Journal of Environmental Quality. 50(1):241-251. https://doi.org/10.1002/jeq2.20175.
DOI: https://doi.org/10.1002/jeq2.20175

Interpretive Summary: Neonicotinoid pesticides are persistent in soils and have been shown to harm aquatic invertebrates, pollinating non-target insects, and insect-eating birds. In this study, we investigated binding and degradation of the neonicotinoid, clothianidin (CTN), in soils collected from eight wetlands managed by the Missouri Department of Conservation. Within each study wetland, soil samples were collected at a depth of 0-10 cm in locations that contained characteristic wetland vegetation for Missouri. Binding of CTN to wetlands soils was relatively weak, indicating that it is mobile and bioavailable in the soil environment. Overall, degradation of CTN was five times faster under anoxic (no oxygen) than oxic (with oxygen) conditions, and CTN degradation increased with increasing soil organic carbon content of the wetland soils. Based on these results, management practices that would increase CTN degradation in wetlands include creating anoxic soil conditions during warm periods of the year to increase CTN degradation rate, and implement strategies to retain or accumulate organic carbon. For the latter, practices include the addition of C-based amendments, such as compost, manure, or biosolids, cover crops, and reduced or no tillage. A major challenge is balancing multiple management objectives in these wetlands, which include row crop production, winter waterfowl habitat, and recreation. Therefore, extending the period of anoxic conditions to facilitate CTN degradation in managed wetland soils will require careful consideration of the impacts on all management objectives. In summary, this work will benefit landowners and land management personnel by demonstrating that managing wetlands to extend anoxic conditions can substantially accelerate CTN degradation in soils and minimize its impact on non-target organisms.

Technical Abstract: 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 non-target taxa, including aquatic invertebrates, pollinating insect species, and insectivorous birds. This study evaluated factors associated with clothianidin (1-[(2-chloro-1,3-thiazol-5-yl) methyl]-3-methyl-2-nitroguanidine, 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 (Kd) 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 (t0.5). Sorption results indicated CTN sorption to wetland soil was relatively weak (average Kd = 3.58 L/kg); thus, CTN has 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 t0.5 =27.2 d; oxic average t0.5 = 149.1 d). A significant negative correlation was observed between anoxic half-life values and soil organic carbon content (r2=0.782; p=0.046). Greater CTN degradation rates in wetland soils under anoxic conditions suggests that managing wetlands to facilitate anoxic conditions could mitigate CTN presence in the environment and reduce exposure to non-target organisms.