SS3.17 Global Mercury Cycling: From Natural to Anthropogenic Sources
Date: Tuesday, June 11, 2002
Time: 11:15:00 AM
Location: Carson C
 
DesJardinsMJ, University of Victoria, Victoria, Canada, watsonm@uvic.ca
Telmer, K, , University of Victoria, Victoria, Canada, ktelmer@uvic.ca
 
COUPLING SOURCES OF ATMOSPHERIC LEAD AND MERCURY INPUTS TO LAKES AND IMPLICATIONS FOR REMOBILIZATION
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The isotopic composition of Pb is a powerful tool for fingerprinting its source and its post-depositional mobility. Results of isotopic ratios from the sequential extractions of sediment cores from Kejimkujik National Park, Nova Scotia, give a clear indication of two sources of Pb: (1) a Paleozoic source which matches local geology, and (2) a geologically older, exotic source which represents airborne long-range transport of particulate Pb. This is confirmed by atmospheric particulates from precipitation obtained within the park that are concordant with the exotic Pb. This “less radiogenic” older source in recent sediments and atmospheric particulates points towards a more “Canadian” than “American” signal. The atmospheric trajectory of Pb should be a reliable proxy for Hg. To capture essential soluble phase information, in-situ porewater samplers were used to obtain detailed profiles of Pb and Hg in the porewater and to measure diagenetic conditions such as pH, dissolved oxygen, redox, diffusion and advection. Results indicate that post-diagenetic processes may cause upward remobilization of Pb and Hg, thereby altering trends otherwise thought to represent historical records of increased heavy metal pollution.