PARTITIONING AND EFFECTS OF SILVER IN AMENDED FRESH-WATER SEDIMENTS

Sediments that represented a wide range of characteristics were amende d with silver compounds to observe partitioning and bioavailability. I n laboratory studies, silver partitioning to particulates, sediment po re water, and overlying water was measured and bioavailability of silv er was determined using Hyalella azteca in 10-day sediment toxicity te sts. Three silver compounds were used as sources of silver for this st udy: silver nitrate, silver chloride, and silver thiosulfate complex. Sediment amendment procedures were adjusted as necessary depending on the characteristics of the individual compounds. Several sediment char acteristics such as organic carbon, pH, redox, and acid volatile sulfi des regulated silver partitioning and bioavailability. Bioavailability of silver was correlated with the overlying water concentration of si lver, Ten-day LC50 values ranged from 1.62 to 379.7 mg Ag/kg for H. az teca exposed to sediments amended with AgNO3. In laboratory experiment s, silver chloride and silver thiosulfate mere orders of magnitude les s toxic and bioavailable than silver nitrate, with 10-day LC50 values greater than the highest concentrations of AgCl and silver thiosulfate complex amended to sediments (2560 and 1125 mg Ag/kg, respectively). (C) 1997 Academic Press.