Concentrations of Metals in Bed Material in the Area of Congaree Swamp National Monument and in Water in Cedar Creek, Richland County, South Carolina

Cooney, Theodore

The Congaree Swamp National Monument is a 15,135-acre flood-plain ecosystem in Richland County, South Carolina. It was officially established in 1976 by an Act of Congress to preserve the last significant tract of southern old-growth river-bottom forest. The Monument's ecosystem supports a wide variety of plant and animal life, and contains numerous trees that are among the largest of their species in the state and nation. This report describes the results of a study by the U.S. Geological Survey, in cooperation with the National Park Service, to document the occurrence of selected metals in bed material in the area of the Congaree Swamp National Monument and in the surface water of a major tributary, Cedar Creek. The study was prompted by concern that trace metals in this valuable flood-plain ecosystem could contaminate and endanger plant and animal life. A total of 37 bed-material samples were collected at 28 sampling stations during two sampling periods (June 18, 1985, and May 28 to June 5, 1986). Results of chemical analyses indicated barium, iron, magnesium, and manganese, which occur naturally in soils in the basins, are present in a wide range of concentrations in the Cedar Creek and Toms Creek watersheds. The highest observed concentrations were 400; 68,000; 35,000; and 1,700 micrograms per gram, respectively. Beryllium, cadmium, lithium, and molybdenum were, if present, in concentrations no greater than minimum detection levels. Overall, concentrations in the Cedar Creek watershed are significantly higher than in the Toms Creek watershed. Relatively high concentrations in samples outside the influence of either Cedar Creek or Toms Creek indicate that the flood plain may act as a sink for certain metals. Ten surface-water samples collected at a site on Cedar Creek were analyzed for selected metals. Concentrations of cadmium, which is a highly toxic element, equaled or exceeded the U.S. Environmental Protection Agency drinking water maximum-contaminant level of 10 micrograms per liter in three samples, with the highest concentration observed being 15 micrograms per liter. Concentrations of manganese equaled or exceeded the U.S. Environmental Protection Agency drinking water secondary maximum-contaminant level of 50 micrograms per liter in seven samples, with the highest observed concentration being 220 micrograms per liter. Copper, zinc, and lead were detected in concentrations less than the U.S. Environmental Protection Agency drinking water secondary maximum-contaminant level, with the highest observed concentrations being 51,270, and 35 micrograms per liter, respectively. Concentrations of barium, beryllium, chromium, cobalt, lithium, and molybdenum were, if present, equal to or less than the minimum detection levels.