University Presentation Showcase: Undergraduate Poster Gallery



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Creation Date

January 2023








Walter S. Borowski

Mentor Department



Contamination by nutrients and fecal microbes is a widespread, chronic problem for surface streams. The Otter Creek watershed covers over 168 square kilometers of north-central Madison County, Kentucky. Contamination sources include urban runoff from the town of Richmond, cattle pasture, and rural and suburban areas that utilize septic systems. Samples were collected from representative sites and measured for dissolved nutrients (ammonium, nitrate, and phosphate) and fecal microbes (total coliform bacteria and Escherichia coli) using colorimetric and IDEXX methods, respectively.

Nutrient concentrations are generally higher than those of pristine streams. Dissolved ammonium concentrations generally lie below ~0.2 mg/L N-NH4 with most samples approaching zero. Nitrate concentration generally lies below 5 mg/L N-NO3 but spike upward at the sewage treatment plant discharge and continue to be high downstream. Orthophosphate displays concentrations below 0.2 mg/L in the entire watershed excepting the sewage treatment plant discharge and stations downstream that show 0.9 to 1.4 mg/L. E. coli concentrations commonly occur between 500 and 1,500 cfu/100 mL within the watershed.

Comparison to a national database allows for assessment of contaminant levels. Median nitrate levels are greater than the national median, whereas ammonium and phosphate levels were lower. The principal source for nitrate and phosphate is a sewage treatment plant that handles waste from Richmond and vicinity. Cattle feces seem to be a major source for ammonium and fecal microbe contamination. E. coli assays show that 60% of sites recommend no extended human contact, making fecal microbes a prevalent contaminant in the watershed.