Time series of trace element concentrations calculated from time series of suspended solids concentrations and RMP water samples: Summary and conclusions

The supply and fate of trace elements in San Francisco Bay, which are partially dependent upon particulate matter in the Estuary, are important management issues. San Francisco Bay receives many waste water discharges, especially in areas south of the Dumbarton Bridge, that contain trace elements that accumulate in benthic organisms (Luoma et al., 1985; Brown and Luoma, 1995). Trace elements tend to adsorb particulate matter (Kuwabara et al., 1989), so the fate of trace elements is partly determined by the fate of suspended solids. Concentrations of dissolved trace elements are greater in the South Bay than elsewhere in San Francisco Bay, and bottom sediments are believed to be a significant source (Flegal et al., 1991). The concentration of suspended particulate chromium in the Bay appears to be controlled primarily by sediment re-suspension (Abu-Saba and Flegal, 1995). Water quality standards for trace elements in the Bay are written in terms of total or near-total trace element concentrations (TEC).

This summary has two objectives. The first is to demonstrate the relationship between suspended solids concentration (SSC) and TEC by developing equations relating SSC to total (or near-total) concentrations of trace elements based on Regional Monitoring Program (RMP) data collected during 1993 and 1994. The second objective is to demonstrate the temporal variability of TEC that are linearly correlated (LCTEC) with SSC by presenting time-series information on LCTEC based on nearly continuous SSC measurements collected during the 1995 water year (October 1, 1994 to September 30, 1995) and the SSC-LCTEC equations.