SS4.02 The Role of Microbiology in Trace Metal and Organic Contaminant Cycling in Aquatic Systems
Date: Wednesday, June 12, 2002
Time: 11:00:00 AM
Location: Esquimalt
 
PoulainAJ, Institut national de la recherche scientifique (INRS), Université du Québec, 2700 rue Einstein, Sainte Foy, QC, G1V 4C7, Canada, alexandre_poulain@inrs-eau.uquebec.ca
Amyot, M, , Institut national de la recherche scientifique (INRS), Université du Québec, 2700 rue Einstein, Sainte Foy, G1V 4C7, Canada, marc_amyot@inrs-eau.uquebec.ca
Barkay, T, , Rutgers University, Department of Biochemistry and Microbiology, 76 Lipman Drive, New Brunswick, NJ 08901-8525, USA, barkay@aesop.rutgers.edu
Hintelmann, H, , Trent Univ., Department of Chemistry, 1600 west bank drive, Peterborough, Ontario, Canada, hhintelmann@trentu.ca
Morel, F, M, Department of Geosciences, 153 Guyot Hall, Princeton University, Princeton, NJ 08544, USA, morel@princeton.edu
Rudd, J, , Freshwater Institute, 501 University Crescent, Winnipeg, MB, R3T 2N6, CANADA, RuddJ@dfo-mpo.gc.ca
Harris, R, , Tetra Tech Inc., 180 Forestwood Drive, Oakville, Ontario, L6J 4E6, CANADA, rharris6@cogeco.ca
 
PHOTOCHEMICAL AND PHOTOBIOLOGICAL FORMATION OF DISSOLVED GASEOUS MERCURY IN A LAKE SPIKED WITH THREE DIFFERENT STABLE ISOTOPES.
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The METAALICUS project aims at clearly establishing the link between atmospheric depositions of mercury and mercury concentrations in fish. Three stable isotopes were added to a lake, its wetland and its upland, and their transport and fate were followed. Here we present results on temporal and spatial distributions of dissolved gaseous mercury, (DGM), the concentration of which influences air/water Hg exchange. In August and September, DGM concentrations were the highest near the surface, then decreased in the epilimnion and in the higher part of the metalimnion. An important peak was observed, in both months, in the bottom of the metalimnion located at 5.5 meters, just below the 1% light cut-off. DGM concentrations also increased above the sediments. Midday increases in DGM levels at the surface and at 5.5 meters are likely partly photo-mediated, since these peaks greatly decreased at night. The metalimnetic and hypolimnetic increases are poorly explained solely by photochemical processes. Photosynthetic activity of organisms may be invoked in the metalimnetic peaks of DGM and the microbial activity of heterotrophic bacteria might be involved just above the sediments.