Tiffany L. Messer
Date of this Version
Lindgren, J. (2020) "Neonicotinoid Pesticide and Nitrate Removal in Floating Treatment Wetlands"
Nutrient and pesticide concentrations in surface water are a growing concern in the Midwest. Floating treatment wetlands (FTWs) are often used to remove excess nutrients from surface water and should be considered for removal of emerging contaminants, such as neonicotinoids. Therefore, the objectives for this research project were: 1) Determine FTW neonicotinoid removal capacity, 2) Quantify neonicotinoid incorporation into floating macrophytes, and 3) Explore potential implications of neonicotinoids on microbial denitrification. A microcosm and mesocosm experiment was completed. The mesocosm experiment evaluated 3 treatments: 1) FTW mesocosm with neonicotinoids, 2) FTW without neonicotinoids, and 3) mesocosm with neonicotinoids and without FTWs. FTW mesocosms exhibited significant removal of imidacloprid (38.3 ± 13.6%) when compared to mesocosms without FTWs. However, for thiamethoxam, mesocosms with and without FTWs had no significant difference in removal. For imidacloprid and thiamethoxam, 23.4% and 8.8%, respectively, was found in the above surface biomass and 6.9% of imidacloprid and 5.2% of thiamethoxam was stored in the below surface biomass. Significant differences were not observed in the nitrate-N removal potential of FTWs when neonicotinoids were present. Additionally, neonicotinoids did not have a significant effect on the abundance of nitrifying and denitrifying genes in the water surrounding FTW roots. The microcosm experiment indicated that denitrifying potential of FTW roots did not change with the addition of neonicotinoids. FTWs have potential to remove neonicotinoids from surface water through biomass incorporation. No evidence supports that the presence of neonicotinoids in the water column lowers the nitrate removing potential of FTWs.
Advisor: Tiffany L. Messer