SS3.07 Headwater Ecosystems in Forested Landscapes and Beyond
Date: Wednesday, June 12, 2002
Location: Poster Session - VCC
 
Alfaro de la TorreMC, Facultad de Ciencias Químicas, Universidad Autónoma de San Luis Potosí, San Luis Potosí, Mexico, alfaroslp@yahoo.com.mx
Tessier, A, , INRS-Eau, Université du Québec, Sainte-Foy (Québec), Canada, atessier@inrs-eau.uquebec.ca
 
CADMIUM BIOGEOCHEMISTRY IN AN ACIDIC PRISTINE LAKE
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Processes controlling the distribution of Cd were investigated in the oligotrophic acidic Lake Tantaré (Quebec, Can.) where the metal input occurs by atmospheric deposition and natural weathering. Dissolved Cd concentration in the water column (~0.3 nM), determined at various times of the year, showed little variation with depth. A mass balance calculation shows that, during the thermal stratification period, the loss of Cd from the epilimnion by the outfall (4.4 mmol/d) is much larger than the loss with settling particles (0.072 mmol/d), indicating that [Cd] in the epilimnion is under physical rather than biogeochemical control. Extensive porewater and geochemical data were also obtained for a dated core. The shape of the vertical profile of sedimentary Cd is mainly explained by the flux of Cd deposited with settling particles and by the flux of dissolved metal across the sediment-water interface by molecular diffusion. Because the benthic community is sparse, transport of dissolved Cd by bioirrigation and bioturbation, and biological mixing of the sediments did not appear to affect the sedimentary Cd profile.