Lead and Strontium in Southeastern North Carolina Surface Waters

Southeastern North Carolina (SENC) hosts three major rivers that are part of two major watersheds that drain a significant area of the central portion of the state. The Cape Fear River is the primary channel in its basin and the Lumber and Waccamaw rivers are tributaries of the Great Pee Dee River. All three rivers pass through wilderness, rural/agricultural, urbanized and industrial areas. Surface waters draining through each of these unique environments contribute to the overall composition of the rivers. Recent studies have shown that the major rivers in SENC host a wide variety of contaminants and are among the most polluted in the country. The work presented here is part of a larger project to assess the origin and fate of Pb and Sr in surface waters across the entire state of NC.

For this project, we performed isotope dilution thermal ionization mass spectrometry (ID-TIMS) analyses for Pb and Sr for river water samples collected from SENC. Filtered water was collected from the Cape Fear, Lumber and Waccamaw rivers and Pb and Sr were isolated using standard column chemistry techniques. Results show that Sr abundance and isotopic composition are closely correlated with local bedrock geology. In contrast, the Pb isotopic compositions of the surface waters do not directly reflect the isotopic composition of the bedrock and is broadly similar to that of leaded gasoline. In addition, Pb concentrations of the river waters increase from western NC to eastern NC.