Influence of Historic and Current Land Use Practices on PCB Contamination of Soils and Stormwater Sediments in the Chesapeake watershed.

Abstract

Polychlorinated biphenyls (PCBs) are persistent organic pollutants (POPs) originating from biphenyl compounds, which were banned in the United States under the Toxic Substances Control Act of 1976. PCBs continue to be detected in various water bodies despite this ban and Total Maximum Daily Loads (TMDLs) have been established in many regions to manage their levels. This study investigates the presence and concentration of PCBs in local soils and roadway sediments, which may become mobilized during stormwater events. Soil and sediment samples from different sites across Anne Arundel County, Maryland, representing various land uses and periods of development were analyzed for 209 PCB congeners, as well as profiles of the ten homologues of chlorinated PCBs. The study correlates PCB concentrations in sediments with land use types (residential, commercial, industrial, greenspace, institutional, energy site) and development eras (before 1970s and after 1970s). The total PCB concentrations ranged from 1.27 to 381 ng/g dry mass. Land use significantly impacted PCB concentration; residential areas (median: 35.6 ng/g) and industry areas (median: 69.8 ng/g) were higher than commercial areas (median: 16.9 ng/g), institutional areas (median: 11.7 ng/g) and greenspace (median: 11.3 ng/g). Within each land use type, no statistically significant differences in total PCB concentrations were observed between pre-1970s and post-1970s development. However, consistent reductions in both median and mean concentrations in post-ban sites indicated a potential influence of development era, with newer infrastructure likely contributing fewer legacy PCB sources. The number of chlorines per biphenyl ranged from 2.48 to 6.11. The toxic equivalency (TEQs) of the PCBs ranged from below 0.0004 to 41.2 pg/g considering all sites. A non-Aroclor congener, PCB 11, was detected in all samples except in greenspace. These findings provide critical insight into PCB distributions across land use and development histories and support efforts to estimate PCB load reduction efficiencies in stormwater control measures, enabling more targeted remediation strategies in high-risk areas.