Author ORCID Identifier
https://orcid.org/0000-0001-9287-1409
Date Available
1-5-2025
Year of Publication
2025
Document Type
Doctoral Dissertation
Degree Name
Doctor of Philosophy (PhD)
College
Agriculture, Food and Environment
Department/School/Program
Biosystems and Agricultural Engineering
Advisor
Dr. Tiffany L. Messer
Abstract
Controlling losses of nitrate-N from agricultural fields to ground and surface water environments is one of the most pressing water resources problems today. Increasing levels of nitrate-N pollution in surface and groundwater is a critical threat to human and environmental health across the globe. To mediate nitrate-N losses, natural and constructed wetlands have been increasingly used as nutrient mitigation technologies and strategies. The use of wetlands as a treatment approach for nitrogen in runoff is a common practice in agroecosystems, however, nitrate-N is not the sole constituent present in agricultural runoff, and other biologically active contaminants have the potential to occur in tandem with nitrate-N. Manure soil amendments are regularly employed in agricultural facilities such as confined animal feeding operations (CAFOs) in order to properly manage animal wastes, however, manure is known to contain high nutrient density, as well as additional agrochemical compounds, adding to the pathways available for agrochemical mixtures to be transported and interact with adjacent aquatic ecosystems. Though antibiotics and nitrification inhibitors may be transformed over time, residues from each have been documented to occur in run-off and affect microbial activity in soil or in saturated sediments. Therefore, a significant and critical knowledge gap exists in how treatment systems will be sustained as agrochemical mixtures evolve. To address this gap, the overall goal of this project is to improve our understanding of the cumulative effect of increased use and occurrence of nitrification inhibitors together with increasing occurrence of veterinary antibiotics residues on nitrogen transformation and loading to aquatic environments. To do this, three objectives were formed: 1. assess the impact of lincomycin (C18H34N2O6S), monensin (C36H62O11), sulfadimethoxine (C12H14N4O4S), and nitrapyrin (C6H3Cl4N) on nitrogen cycle processes in wetland sediments using microcosm incubations, 2. measure nitrate-N reduction in the water of floating treatment wetland mesocosms over time following the introduction of veterinary antibiotic residues 3. identify the fate of veterinary antibiotics and nitrification inhibitors in floating treatment wetlands using mesocosms. The objectives were supported by three experimental seasons (2020, 2022, and 2023) that each included quantitative measurements of the effect of agrochemical mixtures on nitrogen transformations for various nitrate-N loading and agrochemical mixtures. Results from each of the three experimental periods (2020, 2022, 2023) indicate that the presence of veterinary antibiotics and nitrification inhibitors may induce a stimulatory response from microbial communities, leading to increases in nitrate-N removal. Additionally, the nitrate-N removal response was observed largely within the first 48 hours of exposure, suggesting that microbial changes due to agrochemical mixture exposure is limited to the first few days after introduction. Plant uptake was observed in all trials for antibiotics, with the majority of agrochemical residues being observed in the below surface biomass (roots). Nitrapyrin was not observed in any studied environmental compartment (water, plant biomass, soil) after the 10-day exposure period. Findings from this study will provide fundamental understanding of the interactions between nitrification inhibitors and veterinary antibiotics on the processes responsible for microbially-mediated denitrification in floating treatment wetlands and aquatic sediments within agroecosystems. Additionally, insight into agrochemical mixture influences on wetland ecosystem function may allow for new strategies in employing constructed wetlands in the future as agrochemical mixture management technologies.
Digital Object Identifier (DOI)
https://doi.org/10.13023/etd.2024.530
Funding Information
This material is based upon work supported by the United States Department of Agriculture un-der Grant No. 2019-67019-29487.
This project was also supported with funds by the United States Hatch multistate capacity funding grant (W-4045).
Recommended Citation
Russell, Matthew, "INFLUENCE OF AGROCHEMICAL MIXTURES ON NITROGEN TRANSFORMATIONS IN FLOATING TREATMENT WETLANDS" (2025). Theses and Dissertations--Biosystems and Agricultural Engineering. 116.
https://uknowledge.uky.edu/bae_etds/116
