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Mercury dynamics of a temperate forested wetland
1Department of Geography, University of Toronto at Mississauga, 3359 Mississauga Rd., N., Mississauga, Ontario, Canada L5L 1C6.
The Science of the Total Environment
|May 18, 2004
Summary
Wetlands are key mercury methylation sites. This study found a Canadian temperate forested swamp acts as a net source of methylmercury to downstream, influenced by hydrology and organic carbon.
Area of Science:
- Environmental Chemistry
- Ecosystem Science
- Hydrology
Background:
- Wetlands are critical for mercury methylation, but data on diverse wetland types and mercury fluxes are limited.
- Understanding mercury dynamics requires assessing wetland hydrology, water quality, and their influence on mercury species.
- Previous research highlights mercury methylation in wetlands, yet specific flux data across varied wetland types remains scarce.
Purpose of the Study:
- To investigate the linkages between wetland hydrology, total mercury (THg) and methylmercury (MeHg) concentrations and fluxes, and water quality parameters.
- To assess mercury dynamics in a temperate forested swamp in Southern Ontario, Canada.
- To determine if wetland type and hydrologic connectivity influence mercury export.
Main Methods:
- Field sampling in two hydrogeomorphically distinct stream reaches within a temperate forested swamp.
- Monitoring of wetland-stream hydrologic connectivity and water flow conditions.
- Analysis of total mercury, methylmercury, dissolved organic carbon, particulate organic carbon, sulfate, and pH in water samples.
Main Results:
- Hydrologic connectivity between the wetland and stream significantly influenced mercury flux, with highest THg flux during connected flow.
- The wetland functioned as a net sink for THg but a net source for MeHg to the downstream system.
- THg and MeHg concentrations correlated with organic carbon, varying by location and flow; MeHg also showed temporal links with sulfate.
- MeHg fluxes were comparable to those from stagnant, acidic wetlands, despite the studied wetland's short residence times and high pH.
Conclusions:
- Wetland hydrology and organic carbon content are key drivers of mercury dynamics and export.
- Temperate forested swamps can be significant methylmercury sources, irrespective of hydrologic connectivity or pH.
- Further research is needed to understand the full range of wetland contributions to mercury cycling.