Neonicotinoid pesticide and nitrate mixture removal and persistence in floating treatment wetlands

Mesocosm and microcosm experiments were conducted to explore the applicability of floating treatment wetlands (FTWs), an ecologically based management technology, to remove neonicotinoid insecticides and nitrate from surface water. The mesocosm experiment evaluated three treatments in triplicate over a 21‐d period. Floating treatment wetland mesocosms completely removed nitrate‐N over the course of the experiment even when neonicotinoid insecticides were present. At the completion of the experiment, 79.6% of imidacloprid and degradation byproducts and 68.3% of thiamethoxam and degradation byproducts were accounted for in the water column. Approximately 3% of imidacloprid and degradation byproducts and 5.0% of thiamethoxam and degradation byproducts were observed in above‐surface biomass, while ∼24% of imidacloprid and degradation byproducts, particularly desnitro imidacloprid, and 1 yr after exposure), and (c) neonicotinoids do not adversely affect nitrate‐N removal via microbial denitrification. Core Ideas Neonicotinoid and byproducts were present in wetland biomass 21 d after exposure. Neonicotinoid and byproducts persisted in biomass 1 yr after exposure. Neonicotinoid exposure did not adversely affect nitrate‐N removal via denitrification.