Investigating E. coli Contamination in Choccolocco Creek, AL
Type of DegreeMaster's Thesis
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Pathogen loading, specifically high Escherichia coli (E. coli) concentrations, is a major cause for poor surface water quality worldwide. Many rivers and streams are used recreationally, and contamination poses a communal health risk. This study focused on a mixed-use watershed with agricultural, urban, and rural areas that has a history of poor water quality in central Alabama. Our goal was to track fecal contamination within the watershed and determine if anthropogenic input played a significant role in E. coli loading. To test this, we collected water samples at nine sites and quantified E. coli, pharmaceutical and personal care products (PPCPs), major and minor metals, nutrients, and other water quality parameters over 6-months. We utilized the multi-proxy dataset with geospatial context to assess the relationships between land-use and water contamination. PPCPs were frequently detected over the recreational period, including acetaminophen (13% of samples), caffeine (50%), salicylic acid (25%), sucralose (38%), and Bisphenol A (13%). We found a strong, environmentally significant correlation between E. coli concentrations and the total concentration of all PPCPs (r = 0.5075; p-value = 0.0448) and the total number of compounds (r = 0.5339; p-value = 0.0331). Other significant variables that were correlated with E. coli included water temperature, pH, and average total phosphorous. Finally, the multiproxy data was interpreted in a geographic context to understand controls from land-use and the built environment. Sample sites were categorized into pristine, agricultural/rural development, and urban development and enrichment factors were calculated for each site. The agricultural/rural development sites had elevated total PPCP concentrations (3.58, 2.28, and 1.78 ng/L) compared to the pristine site (1) which may be due to a high density of septic systems and low density of municipal sewer infrastructure in the region. Malfunctioning septic systems could contribute to the increased E. coli and PPCP in these areas and our combined results support that idea pointing to a significant anthropogenic loading of E. coli, particularly in agricultural/rural regions of the watershed. In a larger context, our results suggest that malfunctioning septic systems may play a largely unrecognized role in contamination of surface water in mixed land-use watersheds.