No abstract

Aquifer sediment and groundwater chemistry data from 15 Department of Defense facilities located throughout the United States were collected and analyzed with the goal of estimating the amount of natural organic carbon needed to initiate reductive dechlorination in groundwater systems.Aquifer sediments were analyzed for hydroxylamine and NaOH-extractable organic carbon, yielding a probable underestimate of potentially bioavailable organic carbon (PBOC). Aquifer sediments were also analyzed for total organic carbon (TOC) using an elemental combustion analyzer, yielding a probable overestimate of bioavailable carbon. Concentrations of PBOC correlated linearly with TOC with a slope near one. However, concentrations of PBOC were consistently five to ten times lower than TOC. When mean concentrations of dissolved oxygen observed at each site were plotted versus PBOC, it showed that anoxic conditions were initiated at approximately 200 mg/kg of PBOC. Similarly, the accumulation of reductive dechlorination daughter products relative to parent compounds increased at a PBOC concentration of approximately 200 mg/kg. Concentrations of total hydrolysable amino acids (THAA) in sediments also increased at approximately 200 mg/kg, and bioassays showed that sediment CO 2 production correlated positively with THAA. The results of this study provide an estimate for threshold amounts of bioavailable carbon present in aquifer sediments (approximately 200 mg/kg of PBOC; approximately 1,000 to 2,000 mg/kg of TOC) needed to support reductive dechlorination in groundwater systems. O

No abstract

Trace Elements, Semivolatile Organics, and Chlorinated Organic Compounds in Bed Sediments at Fort Gordon anthracene, benzo(a)anthracene, chrysene, benzo(a)pyrene, and pyrene. The most frequently detected organic compounds among bed sediment samples were pyrene, chrysene, and fluoranthene, which were detected in more than 45 percent of sites and reported at concentrations exceeding probable effect levels for the amphipod Hyalella azteca established by the U.S. Environmental Protection Agency. Previous Investigations In 1995, Fort Gordon was assessed as part of a comprehensive water-quality investigation conducted by the U.