Hormone and antibiotic concentrations in surface waters of Delaware

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University of Delaware
Water quality surveys have confirmed the presence of hormones and antibiotics in surface waters of the U.S. Although the reported concentrations of these substances are extremely low, there is substantial concern about their effect on aquatic life and humans. Significant sources of steroid hormones and antibiotics include runoff from agricultural land receiving application of animal manure, discharge from concentrated animal feeding operations (CAFOs), and wastewater treatment plants (WWTPs). This study investigated the concentrations of select hormones and antibiotics in surface waters of Delaware. Our primary hypothesis was that urban and wastewater sources and agricultural watersheds with manure application or animal operations would yield elevated concentrations of these contaminants. Fifty surface water sampling locations (streams, lakes, and ponds) throughout the state of Delaware were chosen based on existing data on hot spots of nitrogen (N) and phosphorus (P) pollution derived from Delaware Department of Natural Resources and Environmental Control (DNREC) surveys. The first set of sampling occurred in spring during wet spring conditions and immediately after land application of manure. The second set of sampling occurred in late summer. Water samples were screened through the cost-effective enzyme-linked immunosorbent assay (ELISA) method followed by more rigorous analyses of selected samples using liquid chromatography with tandem mass spectrometry (LC-MS/MS). ELISA screening included estradiol (E2ß), sulfamethazine (SMZ), and triclosan (TCS), while LCMS/MS quantified the free forms of estrone (E1) and estradiol (E2ß), estrone-3-sulfate (E1-3S), sulfamethoxazole (SMX), sulfamerazine (SMR), and tetracycline (TC). A GIS analysis was performed to delineate watershed boundaries for each of the 50 sampling locations. The proportions of various land uses in each watershed were determined. The measured concentrations of hormones and antibiotics were evaluated against land use as well as N, P, and TOC concentrations. ELISA results were much higher than LC-MS/MS values; previous studies have shown that ELISA tends to overestimate due to cross-reactivity of isomers, degradation byproducts, or structurally related compounds, and therefore we expected lower concentrations from LC-MS/MS. LC-MS/MS results showed that some hormone concentrations in spring exceeded the predicted no-effect concentrations (PNECs), though antibiotic concentrations in spring and both hormone and antibiotic concentrations in late summer were below environmental thresholds. Concentrations were substantially lower in the late summer than the spring. Highest concentrations were observed for agricultural land in Sussex County. The results showed several statistically significant correlations between concentrations and land use types; for example, agriculture and E2ß, and agriculture and E1-3S were both positively correlated at the a = 0.1 level for the April dataset. This suggests that agricultural watersheds yielded elevated concentrations of hormones. Relationships between hormones and antibiotics and N, P, and TOC were weak. Overall, this study suggests that hormone and antibiotic concentrations may not pose a chronic threat to aquatic organisms. Based on this research, land use is only one component for predicting hormone and antibiotic concentrations in surface waters. Strong relationships between hormones and antibiotics and N, P, and TOC may not exist at the watershed scale.