Graduate Studies
First Advisor
Shannon Bartelt-Hunt
Second Advisor
Daniel Snow
Date of this Version
4-2024
Document Type
Article
Citation
A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science
Major: Civil Engineering
Under the supervision of Professors Shannon Bartelt-Hunt and Daniel Snow
Lincoln, Nebraska, April 2024
Abstract
Neonicotinoid insecticides and strobilurin fungicides have seen an increased usage in the United States and globally due to their effective mode of action against pests. However, these pesticides and their degradation products have to been associated with having toxic effects on non-target organisms including bees, aquatic organisms and humans. Consequently, analysis of these pesticides is crucial in understanding their fate in the environment and potential ecotoxicological implications. Optimized methods for extraction and quantification of twenty-two pesticides and their degradation products from water and solid samples using liquid chromatography tandem mass spectrometry (LC-MS/MS) provides a highly sensitive method for their detection. Methods were applied to water samples collected from two streams that received runoff from land-applied wet cake, and spilled wastewater from an ethanol plant that used pesticide-treated seed corn as feedstock. Three different ion sources (electrospray ionization (ESI) source, atmospheric pressure chemical ionization source and UniSpray™ (US) ionization source) were optimized and compared for enhanced performance during the method development. Matrix effects for the three ion sources were evaluated in two matrices (DDI water and wastewater samples). The US showed the lowest matrix effects values among the three sources, with APCI exhibiting more pronounced signal enhancement from matrix. The accuracy and sensitivity of the US was further assessed using method detection limits (MDLs) and recovery efficiency. MDLs range from 0.00189 to 0.0209 µg/L. 6-Hydroxynicotinic acid was not recovered in liquid samples due to its high polarity. The average recovery of the pesticides and their metabolites ranged from 30.61% to 94.35%, with above 60% of the pesticides having an average recovery exceeding 70%. The method was applied to grab water and passive sampler extracts from two streams in Mead, Nebraska, Johnson and ENREEC Creek. The samples were collected monthly at each sampling location from April 2021 to November 2023. Eighteen out of the twenty-two target pesticides were detected with concentrations ranging from below the detection limit.
Advisors: Shannon Bartelt-Hunt and Daniel Snow
Comments
Copyright 2024, Jascika Maclean. Used by permission