Occurrence, source, and toxicity of contaminants of emerging concern in the diverse subwatersheds of the Chesapeake Bay

Author/Creator

Author/Creator ORCID

Date

2022-01-01

Department

Chemical, Biochemical & Environmental Engineering

Program

Engineering, Chemical and Biochemical

Citation of Original Publication

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Abstract

Contaminants of emerging concern (CECs), such as antibiotics, hormones, pharmaceuticals, and UV filters, have been widely used in human and animal health for decades. Many of these compounds are not fully degraded during treatment of animal or human wastes, resulting in the detection of trace concentrations of CECs around the world. The global presence of CECs has raised concerns for human and ecological health; therefore, understanding the concentration, source, and toxicity of CECs is critically important. However, limited data are available on the presence, origin, and ecological impacts of CECs in most aquatic environments. In watersheds with mixed land use (e.g., animal feeding operations, wastewater treatment plants), the ability to distinguish sources remains a challenge. Therefore, this dissertations focused on the identification of priority CECs in the diverse subwatersheds of the Chesapeake Bay and investigations into methods for improving toxicity assays.Antibiotics, hormones, pharmaceuticals, and UV filters, the active ingredients in sunscreens, were proposed as priority CECs due to the associated negative impacts on human and ecological health, such as promotion of antibiotic resistance and endocrine disruption outcomes. The concentrations of over 60 target CECs were measured in water, sediment, and oysters from the Chesapeake Bay over three sampling campaigns. Due to the widespread presence of antibiotics, improvements to the standard broth microdilution antimicrobial activity assay were also investigated to enhance the sensitivity for environmental concentrations. Results from this dissertations highlighted several associations between sources and CECs. For example, sucralose, an artificial sweetener and wastewater indicator, was consistently correlated to the number of septic systems, confirming significant impacts of non-sewered sanitation systems in subwatersheds that also contained wastewater treatment plants. A fluorescence model of dissolved organic matter was developed, and a spectral metric was used as an indicator to identify unknown agricultural or anthropogenic waste sources. Although the spectral metrics were consistently associated with non-point sources, the model was generally non-selective, highlighting the limitations of this technique in large, complex watersheds. Lastly, the sensitivity of the broth microdilution antimicrobial activity assay was improved for three classes of antibiotics. Overall, the comprehensive findings of the interdisciplinary approaches employed in this dissertations provided expanded insights into the occurrence, source, and toxicity of some of the most important CECs in the aquatic environment.