|SS4.06 Speciation, Bioavailability, and Impacts of Atmospheric Trace Metals in Aquatic Systems|
|Date: Wednesday, June 12, 2002|
|Time: 5:00:00 PM|
|Preus, E, M, Frontier Geosciences, Seattle, WA, USA, EveP@FrontierGeosciences.com|
|Bloom, N, S, Frontier Geosciences, Seattle, WA, USA, NicolasB@FrontierGeosciences.com|
|EFFECT OF SELENIUM SPECIES ON MERCURY METHYLATION AND SPECIATION IN LAUCUSTRINE SEDIMENT INCUBATIONS|
|To assess the effect of selenium on methyl mercury formation and mercury speciation in lake sediments, four selenium compounds (Se(IV), Se(VI), C5H11NO2Se, SeCN) were added in varying concentrations to an organic-rich freshwater sediment with high methylation potential. The samples were spiked with 2 ppm Hg(II) and incubated anoxically at room temperature for a week. The sediment was then analyzed for methyl mercury and mercury speciation by a five-step sequential selective extraction process.
In all incubations, the addition of Se suppressed CH3Hg formation compared to control samples. In samples spiked with SeCN, Se(IV) and Se(VI), the amount of CH3Hg produced was inversely proportional to the quantity of Se added. The opposite occurred in samples spiked with C5H11NO2Se, though CH3Hg was lower than the control at the highest C5H11NO2Seconcentration.
The inorganic Hg speciation fluctuated slightly with varying concentration of Se. At higher Se concentrations, less Hg was found in the F3 (organic bound) fraction, and more in the F4 (more strongly bound Hg). Apparently the Se binds with the mercury, reducing its bioavailability, and thereby inhibiting methylation.|