SS3.17 Global Mercury Cycling: From Natural to Anthropogenic Sources
Date: Tuesday, June 11, 2002
Time: 3:00:00 PM
Location: Carson C
LeanD, University of Ottawa, Department of Biology, Ottawa, Canada,
Siciliano, S, , Coupure, Gent, Belgium,
O'Driscoll, N, , University of Ottawa/Department of Biology, Ottawa, Canada,
Dissolved Gaseous Mercury in Lakewaters
Dissolved Gaseous Mercury (DGM) is principally elemental mercury and due to its low solubility and Henry's Law constant can diffuse from surface waters to the atmosphere. As such it is one of nature's way of eliminating mercury from lakes, rivers and wetlands. The principal pathway for DGM formation has been thought to be photochemical. In other words, solar radiation is necessary for the converversion of mercury(II) to DGM. Here we show that there is a significant role for microbial processes as well and demonstrate the tight coupling between photochemical and microbial activity. The importance of microbes is evaluated by relating depth profiles of DGM with mercury reductase and mercury oxidase activity in an unpolluted headwater lake (Jacks Lake) and in Lake Ontario. Photochemical production of DGM is restricted to surface waters but microbial production occurs throughout the water column with high rates observed in the metalimnion and even to the deepest parts of the hypolimnion. This illustrates that models for DGM formation must also include a microbial component.