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Preliminary Geochemical Studies of Pollutant and Natural Organic Compounds in Sediments from Sonoma Baylands - A Wetland Restoration Project in San Francisco Bay, California
Frances D. Hostettler, Wilfred E. Pereira, Keith A. Kvenvolden, David R. Jones, and Fred Murphy

Aliphatic Hydrocarbons

Sediments at the pilot unit are stratified. Whereas concentrations of terrigenous n-alkanes are about the same in the three core horizons, biomarker profiles (triterpanes and steranes) and the presence of an unresolved complex mixture (UCM) of hydrocarbons in the top horizon of the cores indicate the presence of weathered and biodegraded petroleum.

PAHs and DDT

PAHs and DDT chartSediments from both the pilot unit and reference site contain low concentrations of PAHs, with fluoranthene and pyrene as the major compounds, and low levels of the chlorinated pesticide DDT and its degradation products DDE and DDD, with DDE being the major compound. In the pilot unit cores, total PAHs range from 83 to 1350 ng/g, and total DDT from 1 to 7.2 ng/g. The highest values are in the top horizon.

Atomic C/N Ratios

Atomic C/N ratios chartThe ratios in the pilot unit cores range from 8.6 to 10.0. The ratios are higher in the reference core, from 10.8 to 12.8. In general, sediments with high terrigenous organic input would have C/N ratios in the range of 12 to 14, whereas those with marine phytoplankton input would be substantially lower (about 6). The observed values represent a mix of sources which is expected to change with time as the wetland develops.

Sterols

Sterols graphSediments from the pilot unit and the adjacent established wetland were analyzed for several classes of organic compounds. The greatest difference between the sediments from the two locations is in the more polar constituents, especially sterols and fatty acids. These compounds will therefore be used as source tracers to monitor the wetland over several years as it reverts back to its natural state.

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