Adsorption seems to be the dominant process involved in partitioning silver onto sediments. Lake sediment silver levels correlate with organic content. Lake sediment silver concentrations have been reported as being 100 times the level in the overlying water (Freeman 1977). Magnesium dioxide, ferric compounds and clay minerals all have an affinity for silver but manganese dioxide appears to have the strongest affinity. Stream sediments in mineralized areas may average around 930 µg/kg while sediments for non-mineralized areas are about 140 µg/kg (Boyle 1968). Analyses of some US stream sediments gave a range of 300 to 1500 µg/kg with the high values being from industrialized mining areas (Turekian et al. 1967).
Sediment enrichment by silver is accompanied by enrichment of barium, strontium, lead, arsenic and antimony. Silver enrichment is highest in sediments with high manganese (Boyle 1968), and enrichment increases as particle size decreases (McDuffie et al. 1976). This is typical of many metals due to the increased surface area available for adsorption.
Deep sea sediments average 110 µg/kg of silver (Turekian et al. 1961). The silver adsorbed to manganese and other suspended river sediments is virtually all released on contact with seawater (Kharker et al. 1968, Dyck 1968, Chao et al. 1974). Silver is readily available from many types of sediments and shellfish concentrations correlate well with most non-crystalline silver extractions (Luoma and Jenne 1976). Silver is reported at 14 to 20 mg/kg in the bottom sediments of California coastal basins (Friberg et al. 1986).