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

Authors: LINDGREN, JULIA - University Of Nebraska; MESSER, TIFFANY - University Of Nebraska; Miller, Daniel; SNOW, DANIEL - University Of Nebraska; FRANTI, THOMAS - University Of Nebraska

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/30/2022
Publication Date: 10/6/2022
Citation: Lindgren, J.K., Messer, T.L., Miller, D.N., Snow, D.D., Franti, T.G. 2022. Neonicotinoid pesticide and nitrate mixture removal and persistence in floating treatment wetlands. Journal of Environmental Quality. https://doi.org/10.1002/jeq2.20411.
DOI: https://doi.org/10.1002/jeq2.20411

Interpretive Summary: Mesocosm and microcosm experiments were conducted to explore how simulated runoff containing neonicotinoid insecticides and nitrate were treated in floating treatment wetlands (FTWs), an ecologically based management technology. The FTW mesocosms completely removed nitrate-N over the course of the experiment even when neonicotinoid insecticides were present. 23.4% of imidacloprid and 8.8% of thiamethoxam were observed in above surface biomass, while 6.9% of imidacloprid and 5.2% of thiamethoxam were found in the below surface biomass. However, 1 year following the experiments, imidacloprid, thiamethoxam, and degradation byproducts were significantly lower in the above and below surface biomass. Comparing the microbial communities of mature FTWs grown with or without neonicotinoids, water column samples had similar low abundances of bacteria involved in nutrient transformations (nitrification and denitrification). Follow up laboratory incubations found highest denitrification activities in FTW plant roots compared to water column samples, and there was no effect of neonicotinoid addition (100 ppb) on potential denitrification activity. Based on these findings, i) FTWs removed neonicotinoids from surface water through biomass incorporation, ii) neonicotinoids do not persist in plant biomass long-term (> 1 year following exposure), and iii) neonicotinoids did not impact microbes involved in nitrate-N removal.

Technical Abstract: 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-day period. FTW mesocosms completely removed nitrate-N over the course of the experiment even when neonicotinoid insecticides were present. 23.4% of imidacloprid and 8.8% of thiamethoxam were observed in above surface biomass, while 6.9% of imidacloprid and 5.2% of thiamethoxam were found in the below surface biomass. However, 1 year following the experiments, imidacloprid, thiamethoxam, and degradation byproducts were significantly lower in the above and below surface biomass. Comparing the microbial communities of mature FTWs grown in the presence and absence of neonicotinoids, water column samples had similar low abundances of nitrifying Archaeal and bacterial amoA genes (below detection to 10^4 mL-1) and denitrifying bacterial nirK, nirS, and nosZ genes (below detection to 10^5 mL-1). Follow up laboratory incubations found highest denitrification potential activities in FTW plant roots compared to water column samples, and there was no effect of neonicotinoid addition (100 ppb) on potential denitrification activity. Based on these findings, i) FTWs were observed to remove neonicotinoids from surface water through biomass incorporation, ii) neonicotinoids do not persist in biomass long-term (> 1 year following exposure), and iii) neonicotinoids did not adversely affect nitrate-N removal via microbial denitrification.