A 5-month partial study (February to July 1983) was completed in Suisun Bay, a shallow embayment of San Francisco Bay, Calif., to determine characteristic heavy metal concentrations present in sediments and organisms (Corbicula clams) prior to possible discharge of San Luis Drain irrigation tile return water. Preliminary results show sediments are typical of other San Francisco Bay study sites, ranging from coarse sands to fine silt-clays. The sediments are enriched in manganese and low in organic carbon; iron is moderately enriched, with acid-extractable iron concentrations of 162-3,521 micro-g/g. Sediment concentrations of silver, zinc, lead, and cadmium measured between April and July are reported. Previous area studies have shown increased concentrations during autumn and winter, a period not covered in the data set. Due to insufficient data, interpretations are incomplete. Clam-tissue burdens for silver and zinc are similar to those found in Corbicula from pristine areas. Lead concentrations are typically below the 2-micrograms/g detection level. Corbicula do show indications of more tissue enrichment for cadmium and copper at estuarine stations than at riverine stations.
