Historical trends of trace metals in a sediment core from a contaminated tidal salt marsh in San Francisco Bay |
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Authors: | Hyun-Min Hwang Peter G Green Thomas M Young |
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Institution: | (1) Department of Civil and Environmental Engineering, University of California, One Shields Avenue, Davis, CA 95616, USA |
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Abstract: | Sedimentation of metals preserves historical records of contaminant input from local and regional sources, and measurement
of metals in sediment cores can provide information for reconstruction of historical changes in regional water and sediment
quality. Sediment core was collected from Stege Marsh located in central San Francisco Bay (California, USA) to investigate
the historical input of trace metals. Aluminum-normalized enrichment factors indicate that inputs from anthropogenic sources
were predominant over natural input for Ag, Cu, Pb, and Zn. Among these, lead was the most anthropogenically impacted metal
with enrichment factors ranging from 32 to 108. Depth profiles and coefficients of variation show that As, Cd, and Se were
also influenced by anthropogenic input. The levels of these anthropogenically impacted metals decline gradually towards the
surface due to regulation of the use of leaded gasoline, municipal and industrial wastewater discharge control, and closure
of point sources on the upland of Stege Marsh. Although trace metal contamination is expected to be continuously declining,
the rates of decline have slowed down. For lead, it is estimated to take 44, 82, and 153 years to decrease to probable effects
level (112 μg/g), the San Francisco Bay ambient surface sediment level (43.2 μg/g), and the local baseline levels (5 μg/g),
respectively. Some metals in surface sediments (0–6 cm) are still higher than sediment quality guidelines such as the probable
effects level. To further facilitate the recovery of sediment quality, more efficient management plans need to be developed
and implemented to control trace metals from non-point sources such as stormwater runoff. |
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Keywords: | Sediment core Metals Enrichment factors Anthropogenic input Tidal salt marsh |
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