Sedimentary record of anthropogenic and biogenic polycyclic aromatic hydrocarbons in San Francisco Bay, California

Dated sediment cores collected from Richardson and San Pablo Bays in San Fr ancisco Bay were used to reconstruct a history of polycyclic aromatic hydro carbon (PAH) contamination. The sedimentary record of PAHs in Richardson Ba y shows that anthropogenic inputs have increased since the turn of the cent ury, presumably as a result of increasing urbanization and industrializatio n around the Bay Area. Concentrations range from about 0.04-6.3 mu g g(-1). The dominant origin of the PAHs contributing to this modern contamination is from combustion processes. Depth profiles in San Pablo Bay indicate high er concentrations of PAHs since the 1950s than during the late 1800s, also presumably resulting from an increase in urbanization and industrialization . Total PAHs in San Pablo Bay range from about 0.04-1.3 mu g g(-1). The rat ios were sensitive indicators of methylphenanthrenes/phenanthrene and (meth ylfluoranthenes + methylpyrenes)/fluoranthene of anthropogenic influences i n the estuary. Variations in the ratio of 1,7-dimethylphenanthrene/2,6-dime thylphenanthrene indicate a gradual replacement of wood by fossil-fuel as t he main combustion source of PAHs in San Francisco Bay sediments. The profi le of perylene may be an indicator of eroding peat from marshlands. (C) 199 9 Elsevier Science B.V. All rights reserved.