Heyvaert, A. C.. University of California-Davis, acheyvaert@ucdavis.edu
Reuter, J. C.. University of California-Davis, jereuter@ucdavis.edu
Slotton, D. G.. University of California-Davis, dgslotton@ucdavis.edu
Goldman, C. R.. University of California-Davis, crgoldman@ucdavis.edu

 
HISTORICAL ATMOSPHERIC DEPOSITION OF LEAD AND MERCURY RECONSTRUCTED FROM SEDIMENT CORES OF LAKE TAHOE, CALIFORNIA AND NEVADA.
 
Substantial trace metal enrichment of modern sediments at Lake Tahoe is attributed to atmospheric deposition, since there are no known direct industrial discharges within the watershed. Before 1850 sediment concentrations of Pb and Hg were similar to bedrock concentrations, indicating that preindustrial contributions came primarily from erosion of local soils. Above these baseline values, however, surface sediment concentrations have increased six-fold for Pb (average 83 ppm) and five-fold for Hg (average 0.191 ppm). Notably, while Pb concentrations have stabilized or decreased in recent sediments, the Hg concentrations have continued to increase. At Lake Tahoe the watershed to lake surface ratio is only 1.6. Therefore, sediment accumulation rates for Pb and Hg in excess of their baseline fluxes are interpreted directly as atmospheric deposition rates: approximately 14 mg Pb and 36 ug Hg per square meter annually. The ratios of total modern flux to preindustrial flux are 25 for Pb and 21 for Hg. While the Pb flux ratio is somewhat higher than reported from the eastern US and Canada, it is not atypical. The Hg flux ratio, however, is much higher than observed in most other natural aquatic systems without direct contamination.
 
Day: Friday, Feb. 5
Time: 03:45 - 04:00pm
Location: Sweeney Center
 
Code: CS63FR0345S