Chemical ingredients from pharmaceuticals, household items, and personal care products are commonly detected in the environment. There are numerous pathways for chemicals to enter the environment, including incomplete removal at wastewater treatment plants and runoff from urban streets and agricultural fields. Pollutants can undergo various transformation processes in the environment to form new (and potentially more toxic) substances. This dissertation evaluated the source, potential risks, and/or persistence of two groups of chemicals, hydroxylated polybrominated diphenyl ethers (OH-BDEs) and antibiotics, in natural and man-made systems using spatial and historical trends. Profiles in dated sediment cores were used to determine historical trends of chemical pollution. OH-BDEs are of particular interest because they have both anthropogenic (transformation products of brominated flame retardants) and natural sources (production by microbiota in marine systems). Also, select OH-BDE congeners photodecompose into dioxins, one of the most toxic classes of chemical pollutants. This work demonstrated that wastewater effluent had little impact on OH-BDE levels. Natural production appeared to be the dominant source of OH-BDEs and brominated dioxins in the studied systems, but the abundance of OH-BDEs was likely indirectly enhanced by anthropogenic activities. Antibiotics are one of the greatest inventions of the 20th century, but their presence may be encouraging the rise and spread of antibiotic resistance genes (ARGs). Antibiotics are used for human chemotherapy, as well as by the agricultural industry as preventative treatments and growth promoters. Here, the historical trends of antibiotics were investigated in four Minnesota lakes, and the spatial distribution of antibiotics in a small lake and the Minnesota and Mississippi rivers were also measured. Wastewater effluent appears to be the primary source of antibiotics in the studied lakes, with lesser inputs from agricultural activities and natural production. The spatial distribution of antibiotics in the small and large-scale systems captured both human and animal-uses, but differing transport processes likely influenced the observed trends in the small and large-scale systems. The overall result of this dissertation demonstrated that presence of select OH-BDE congeners and antibiotics in the studied systems was enhanced (either directly or indirectly) by human activities. Increasing our understanding about anthropogenic sources of emerging contaminants will be beneficial in implementing future efforts to reduce the human chemical footprint.
University of Minnesota Ph.D. dissertation.August 2017. Major: Civil Engineering. Advisor: William Arnold. 1 computer file (PDF); xix, 263 pages.
Investigating the drivers of chemical pollution: A spatial and historical analysis of emerging organic contaminants in aquatic and engineered systems.
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