Partitioning and effects of silver in amended freshwater sediments

Sediments that represented a wide range of characteristics were amended with silver compounds to observe partitioning and bioavailability. In laboratory studies, silver partitioning to particulates, sediment pore water, and overlying water was measured and bioavailability of silver was determined using Hyalella azteca in 10-day sediment toxicity tests. Three silver compounds were used as sources of silver for this study: 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 characteristics such as organic carbon, pH, redox, and acid volatile sulfides regulated silver partitioning and bioavailability. Bioavailability of silver was correlated with the overlying water concentration of silver. Ten-day LC50 values ranged from 1.62 to 379.7 mg Ag/kg for H. azteca exposed to sediments amended with AgNO3. In laboratory experiments, silver chloride and silver thiosulfate were orders of magnitude less 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.