PARENT SESSION
MA7 - Mercury: Fate, Transport, & Bioaccumulation
Chair: Kidd, Karen¹, ¹ Freshwater Institute, Winnipeg, MB
8:00 AM to 12:00 PM - Monday, 18 November 2002
Room Ballroom A

(220) Site-Specific Conditions and Methyl Mercury Formation in Aquatic Systems .

Bonzongo, Jean-Claude^*,1, ¹ Dept. of Environ. Eng. Sces, P.O. Box 116450, University of Florida, Gainesville, FL, USA

ABSTRACT- Laboratory experiments using sediment slurries were conducted to assess the potential effects of selected human-imposed conditions to aquatic systems on the transformation of sedimentary ambient mercury (Hg). Unlike previous Hg methylation and demethylation studies, which are based on measurements of potential rates of added Hg²⁺-methylation and methyl-Hg demethylation, changes in the speciation of Hg naturally present in sediment were tracked down after addition of pollutants other than Hg-compounds to simulate the impact of different land-use types. Based on both trends obtained from laboratory experiments and hypotheses derived from the literature, aqueous Hg data determined on water samples collected from sites with identifiable human impacts and hypothesized to have contrasting methyl-Hg levels were analyzed to assess the effect of site-specific conditions on in situ levels of methyl-Hg in the Mobile-Alabama River System (MARS). In addition to confirming some anticipated trends, such as the effect of sulfate and pH on methyl-Hg levels, the study points out the importance of bedrock geology; as well as the potential role of organic matter and nutrients addition on Hg transformations.

Key words: Land use, Aquatic systems, mercury transformation, methylmercury