PARENT SESSION
Organized Oral Session 5: Mercury cycles: Sources, mass balances, bioaccumulation, and options to manage affected systems
Organizer(s): EPH Best, JG Wiener, and D Planas
Monday, August 8, 8:00 AM - 11:30 AM, Meeting Room 511 C, Level 5, Palais des congrès de Montréal
METAALICUS: A whole ecosystem loading experiment evaluating the biomagnification and fate of mercury.
Hintelmann, Holger*,1, 1 Department of Chemistry, Peterborough, Ontario, Canada
ABSTRACT- A whole-ecosystem multi-disciplinary project, "Mercury Experiment To Assess Atmospheric Loadings In Canada and the Unites States" (METAALICUS) is under way at the Experimental Lakes Area (ELA) in Northwestern Ontario, Canada. To evaluate the relationship between atmospheric loading and ensuing Hg concentrations in fish, the Hg load to Lake 658 at the ELA was increased by addition of Hg enriched with 202Hg(II). Simultaneously, the forested upland and a wetland were amended with 200Hg(II) and 198Hg(II), respectively. The Hg loading started in 2001 and commenced in the following years. 2005 marks the fifth (and last) year of isotope additions to the lake. The application of stable isotopes of Hg allows us to monitor the fate of newly added Hg separately from Hg already present in the system. The lake ecosystem responded very rapidly to the addition of new Hg. The total Hg concentrations in surface water approximately doubled during the experiment. Methylated Hg was detected within weeks of additions in lake water, suspended material, and biota, including zooplankton and fish. Concentrations of new methylmercury continued to increase during the study period and comprise now approx. a third of the overall Hg in biota. Initial data suggest that the added new mercury is more bioavailable for methylation reaction compared to old Hg. Conversely, the terrestrial systems is slow to export newly deposited Hg to the lake. Less than 1 % of the annual Hg loaded is currently mobilized.
Key words: mercury, methylmercury, atmospheric loading, stable isotopes