PFAS in the environment have recently received massive attention as an emergent forever chemical group of widespread occurrences. The Pee Dee watershed with is eight rivers (Lumber, Little Pee Dee, Lynches, Great Pee Dee, Waccamaw, Black, Pocatalico, Sampit) across 14 counties and 27 local watersheds has, however, been largely understudied, probably due to the absence of major industrial hubs. This watershed hosts a dispersed distribution of numerous local textile, polymer/plastic, chemical and other PFAS-related industry and wastewater management facilities, but also contains two major airbases with their legacy footprint, and receives influx from highly contaminated neighboring areas in North Carolina as well.

This project, co-funded by SC Sea Grant and SC office of Resilience, aims at determining the PFAS concentrations in waters and soils within the SC Pee Dee watershed with the goal to trace back sources, understand dispersal, dilution, and concentration behavior, and analyze exposure of local communities. It also asks the question, how PFAS concentrations across this wetland-dominated region might be influenced by changing climatic parameters and during storm/flooding conditions.

Out on the 130 water samples collected since July 2024, 23% could be counted as PFAS unobjectionable. The overall average of 106 ng/kg total PFAS is high but not a very meaningful number, since the concentrations are significantly elevated downstream of certain industrial sources and land-use practices: some WWTP outlets, wastewater effluent land application sites (spray fields), some landfills, legacy industrial sites (DuPont, Galy & Lord); with maxima below the two airbases (Myrtle Beach Midway Swash: >6,000 ng/kg). A plume of legacy and new-generation PFAS seems to drain over from the hotspots (Chemours among others) in neighboring counties in North Carolina through the Lumber and Little Pee Dee Rivers.

While very high PFAS concentrations seem to become diluted during downstream transport or absorbed by the river-surrounding wetland swamps, PFAS levels below a hundred ng/kg appear to remain elevated on their downstream journey. The only significant reduction in PFAS concentrations happens where a stream enters the coastal brackish influence that quickly leads to a dilution towards unproblematic concentration levels.

The results will now be compared to the environmental measurements we conducted and integrated with available economic, social, and environmental data in a comprehensive GIS project.