Characterization of the Ashepoo-Combahee-Edisto (ACE) Basin, South Carolina
Hydrochemistry and Pollution
Chemical contamination in the ACE Basin may originate from atmospheric, terrestrial, and aquatic sources and include point and nonpoint source pollution. Once introduced into the system, the fate of pollutants is modulated by a number of physical factors such as organics, pH, salinity, and humic acids. Several studies have been conducted in the ACE Basin to examine the level of chemical contaminants in the sediment, which is the primary environmental sink for pollutants. The overall level of sediment contamination in the ACE Basin study area was found to be low with very little potential for adverse biological effects. Scott et al. (1998) found only arsenic in high enough concentrations to exceed the ER-L level, which is the concentration at which 50% of the studies found there to be significant negative effects on organisms. Ten of 34 study sites had sediment arsenic concentrations exceeding the ER-L level but not the ER-M level, or the point where 10% of the studies noted significant negative effects on organisms. These high levels are due to naturally occurring arsenic concentrations in the basement rock within the region. Scott et al. (1998) found concentrations of PAHs, PCBs and organochlorine pesticides to be below ER-L levels at 34 study sites within the ACE Basin. Another study of sediment contamination within the ACE Basin found one site on the South Edisto River near Bear Island Wildlife Management Area to have exceeded the ER-L level for five tested contaminants: arsenic, chromium, nickel, P,P'-DDD, and total DDT. The source of the contaminants at this site is unknown. While sediment contamination in the ACE Basin is generally at acceptable levels, it is important that land use planning in the region limit new sources of pollutants.