Tidal creek and salt marsh sediments in South Carolina coastal estuaries: I. Distribution of trace metals

Twenty-eight tidal creeks were sampled along the South Carolina coast in th e summer of 1995 to determine the levels of sediment trace metal contaminat ion associated with different types and varying levels of human development in their watersheds. The particle size and total organic carbon (TOC) cont ent of creek sediments in developed watersheds (i.e., industrial, urban, an d suburban) were similar to that in watersheds with little or no developmen t (i.e., forested or reference). Those trace metals commonly associated wit h urban and industrial sources, including Cu, Cr, Pb, Zn, Cd, and Hg, were in significantly higher concentrations in tidal creeks located in industria l/urban watersheds compared to the suburban and forested watersheds. Sedime nt trace metal concentrations were similar for creeks located in suburban a nd forested watersheds and 2 to 10 times lower than the creeks located in i ndustrial/urban watersheds. Concentrations of trace metals primarily associ ated with the natural weathering of basement rock, including Al, Fe, As, Ni , and Mn, were not significantly different among watershed types. Four of t he tidal creek-salt marsh systems were extensively sampled from the creek c hannel to the marsh-upland interface to characterize sediment trace metal s patial distributions within creek-marsh systems. Sediment particle size, TO C, and trace metal concentrations varied spatially within each creek-marsh system depending on the type of development in the watershed and the probab le source of metals. The creek-marsh system selected to represent the indus trial development had significantly higher "anthropogenic" trace metal conc entrations compared to the other creek-marsh systems. This system also had trace metal distributional patterns that appeared to be associated with sev eral localized sources of metals on the marsh surface. Both the "anthropoge nic" and "natural" trace metal concentrations and spatial distributions wer e similar among and within the forested and suburban creek-marsh systems.