Time Series Models of Silver and Lead Contamination in San Francisco Bay
Abstract
Measurements of silver and lead concentrations in San Francisco Bay waters from 1989 to 1998, along with associated water quality parameters, provide new insights into their biogeochemical cycling within the estuary. Both elements have similar biogeochemical properties and both have been relatively enriched in the estuary by anthropogenic inputs (dissolved trace metal decadal mean: Ag ~ 5.7 ng kg-1 and Pb ~ 31 ng kg-1 in the southern reach). Time series models confirm that dissolved lead concentrations have remained essentially constant over the past decade, as previously indicated by stable lead isotopic composition measurements and mass balance calculations. Conversely, the models show statistically significant decreases in dissolved silver concentrations over the same time period. This disparity is consistent with the differences in contemporary anthropogenic inputs of those metals to the estuary, where there has been a 3-fold decrease in industrial silver inputs over the last decade, but where industrial lead inputs have remained relatively high due to the persistent discharge of historic industrial lead deposits in its drainage basin.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2001
- Bibcode:
- 2001AGUFM.H12A0271S
- Keywords:
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- 1065 Trace elements (3670);
- 1800 HYDROLOGY;
- 1803 Anthropogenic effects