DETERMINING THE SOURCES OF POLLUTION AT AN URBAN STREAM USING WATER ISOTOPES

Anthropogenic influences in urban areas have a significant impact on water quality in nearby catchments. The goal of this study was to determine the sources of pollution to an urban creek in the Charleston, SC metropolitan area using a combination of chemical analytes such as major and minor ions as well as water isotopes. This study focused on Filbin Creek in North Charleston, an urban freshwater stream that discharges into a tidal estuary. Based on it’s inclusion on the EPA 303(d) list of impaired water ways and the ephemeral nature of the stream, Filbin Creek serves as an example of problems being faced by many urban catchments. We hypothesize that that (i) runoff from surrounding highways and developments introduces pollutants into Filbin Creek and (ii) storm events were the most significant contributors to stream volume. We sampled precipitation and surface water from different stretches of this stream and analyzed these samples for ions, heavy metals, and water isotopes. Results indicated elevated levels of various pollutants which exceed EPA standards (including Cr, Fe, NO₃^-, PO₄^3-, and Zn) in both precipitation and surface water, particularly following rain events. Most pollutant levels increased after rain events supporting our initial hypotheses. Water isotopic signatures suggested a high volume of input from isotopically-depleted runoff and precipitation in comparison to the more isotopically-enriched baseline of the surface water. The findings of this study signify a need for a more comprehensive assessment of the health of urban waterways like Filbin Creek.