METHOD DEVELOPMENT FOR THE QUANTITATION OF NEONICOTINOID LEACHING FROM COMMERCIAL POTATO PRODUCTION
Date
2025-01-17Author
Betz, Carl
Department
Environmental Chemistry and Technology
Advisor(s)
Ginder-Vogel, Matthew
Metadata
Show full item recordAbstract
The contamination of groundwater with pesticides is a global threat to human and environmental health. Groundwater serves as a major drinking water source, and pesticides are frequently detected in groundwater in intensively farmed regions. Residents of rural areas with agricultural land use often rely on private wells without testing or treatment requirements, increasing their risk of exposure to groundwater contamination. Irrigated specialty crop production is often conducted in well-drained soils where pesticides can quickly leach into groundwater. The purpose of this thesis was to develop a field sampling method and an analytical method for the quantitation of neonicotinoid insecticide leaching in sandy soils. For the field sampling method, passive capillary samplers (PCAPS) were designed and their ability to measure water fluxes through sandy soil was evaluated through laboratory experiments and a field study at the University of Wisconsin Hancock Agricultural Research Station. The results of the PCAPS evaluation revealed that a large number of wicks, a small PCAPS pan surface area, and divergence control collars were necessary to achieve high collection efficiencies in well- drained soil. In the field experiment, percolation measurements from the PCAPS were highly variable indicating the need for substantial replication to obtain representative percolation estimates over large areas. To quantify the concentrations of the neonicotinoids imidacloprid, thiamethoxam, clothianidin, and their environmental transformation products in soil pore water samples collected from the PCAPS, a high-throughput liquid-chromatography tandem mass spectrometry (LC-MS/MS) method with a solid phase extraction (SPE) pretreatment step was developed. The SPE method using Waters Oasis HLB SPE cartridges provided high recoveries (>85%) for all target compounds in synthetic groundwater except for the desnitro-imidacloprid transformation product. The LC-MS/MS method precision was low during development with
relative standard deviations exceeding 10% for many target compounds during repeat injections of neonicotinoid standards. Mass spectrometer scans of diluent blank and neonicotinoid standard injections revealed that matrix effects due to coeluting solids were a likely cause of the low precision of the method. Future work improving the separation of target compounds from matrix interferences and the addition of isotope-labeled internal standards could improve the LC- MS/MS method performance. Together, the PCAPS designed in this thesis and the LC-MS/MS method developed provide valuable tools for pesticide monitoring in sandy soils.
Subject
Environmental Chemistry and Technology
Permanent Link
http://digital.library.wisc.edu/1793/90778Type
Thesis