Glob. Biogeochem. Cycles http://doi.org/fxp935 (2012)
Terrestrial vegetation impedes the transport of mercury from the atmosphere to freshwater systems, according to watershed-scale experiments. Once mercury enters aquatic environments, it can accumulate up the food chain, contaminating fish and the mammals that prey on them.
Jennifer Graydon of the University of Alberta and colleagues examined the fate of isotopically labelled mercury added annually to a watershed in northwestern Ontario, Canada, between 2001 and 2006. They monitored the mercury content of litterfall and ground and canopy vegetation, together with emissions from the canopy surface, over the course of each year. Around 11% of the mercury added to upland and wetland forest canopies was retained; the rest was either lost to the atmosphere or escaped to the lower canopy. In contrast, around 65% of the mercury deposited on ground vegetation was retained.
The researchers suggest that ground vegetation can act as a temporary reservoir for mercury in boreal forests, delaying the contamination of groundwater and adjacent freshwater environments.
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