Historical trends of metals in the sediments of San Francisco Bay, California

摘要: Abstract Concentrations of Ag, Al, Cr, Cu, Fe, Hg, Mn, Ni, Pb, V and Zn were determined in six sediment cores from San Francisco Bay (SFB) one core Tomales (TB), a reference estuary. SFB collected between the head estuary its mouth (Grizzly Bay, GB; Pablo SP; Central CB; Richardson RB, respectively) ranged length 150 to 250 cm. Ni are greater than mean crustal content TB sediments, found many other coastal sediments. However, erosion ultramafic rock formations watershed appears be predominant source. Baseline concentrations metals horizons deposited before sediments influenced by human activities comparing those TB. Cu co-varied with Al 23.7±1.2 μg/g 41.4±2.4 μg/g. less variable: 0.09±0.02 μg/g; 5.2±0.7 0.06±0.01 Zn, 78±7 The earliest anthropogenic influence on metal appeared as Hg contamination (0.3–0.4 μg/g) at SP 1850 1880, apparently associated debris hydraulic gold mining. Maximum within 20 times baseline. Greater inventories GB RB verified importance mining Enrichment first after 1910 core, later is observed Europe or eastern North America. Ag Pb 5–10 baseline three Large result proximity large smelter. Inventories similar typical atmospheric inputs, although smelter also suspected. have decreased since 1970s (to 0.30 25 μg/g, among all 1990. Early was perhaps byproduct smelting process, but modern source indicated, especially CB.