Clothianidin decomposition in Missouri wetland soils

Area of Science:

• Environmental Chemistry
• Soil Science
• Ecotoxicology

Background:

• Neonicotinoid pesticides, like clothianidin (CTN), persist in soils and can contaminate water.
• Negative impacts on non-target organisms, including aquatic invertebrates and pollinators, are documented.
• Wetland soils may play a role in mitigating neonicotinoid environmental risks.

Purpose of the Study:

• To evaluate clothianidin (CTN) degradation and sorption in Missouri wetland soils.
• To assess the potential of wetland soils to mitigate environmental risks posed by neonicotinoids.
• To determine factors influencing CTN fate in wetland environments.

Main Methods:

• Determined solid-to-solution partition coefficients (K_d) for CTN sorption in eight wetland soils.
• Conducted CTN sorption isotherm experiments on two contrasting soils.
• Measured CTN degradation under oxic and anoxic conditions over 60 days, fitting data to kinetic decay models to find half-lives (t_0.5).

Main Results:

• CTN sorption to wetland soils was weak (average K_d = 3.58 L kg^-1), indicating potential mobility and bioavailability.
• Anoxic conditions significantly increased CTN degradation rates (anoxic average t_0.5 = 27.2 d) compared to oxic conditions (oxic average t_0.5 = 149.1 d).
• A significant negative correlation was found between anoxic half-life and soil organic carbon content (r² = .782, p = .046).

Conclusions:

• Wetland soils exhibit weak sorption for CTN, suggesting potential for movement.
• Anoxic conditions in wetlands substantially accelerate CTN degradation.
• Managing wetlands to promote anoxia could be a viable strategy to reduce environmental CTN levels and protect non-target organisms.