Historical data review and source analysis of PCBs/Arochlors in the Lower Leon Creek Watershed

PCBs have been banned since the late 1970s, but concentrations still exist in sediments and riverine fish and continue to exceed regulatory limits which can result in negative health effects. This study looks at historical records of PCB and Arochlor concentrations in surface water, sediments, and fish tissue for the Lower Leon Creek, Bexar County in Texas. Temporal analysis on the concentrations of PCBs and Arochlors was conducted for detection and exceedance of selected screening criteria. In addition, the half-lives of select PCB congeners were calculated for 2007-2012 data to ascertain differences in PCB concentrations with their hydrophobicity. Source analysis was conducted to determine the potential contributing sources of PCB contamination using source data (landfills, outfalls, etc.) and the PCB exceedance data. For sediment and fish tissue sampling results, historic data shows high concentrations of PCB/Arochlors over the course of several decades. The historical data is characterized as being widely variable for detections in Arochlors and concentrations between years, with a dramatic drop in concentrations detected starting in 2009. Overall, the sampling locations adjacent to and downstream from the former Kelly Air Force Base have the highest concentrations of PCB/Arochlors over the longest period of time. The results of this work will aid regulatory agencies in addressing impairment.