Mercury

A key for understanding how mercury moves from the atmosphere into fish and wildlife is to know where Hg accumulates in the landscape. Basically, forest canopies are very effective scavengers of atmospheric Hg, whether Hg is in gaseous, water-dissolved, or particulate form. Hg, once captured at canopy level, is transferred to the forest floor, gradually and seasonally, through litter fall. Depending on local soil drainage, part of this Hg becomes methylated, and is rendered toxic through the trophic process of bio-accumulation. Some of the Hg stored in the forest floor is recycled through vegetative uptake, with mycelial Hg ubtake and subsequent transfer to fungal fruiting bodies (mushrooms) providing a pathway for terrestrial Hg bio-accumulation. As water percolates over and through watershed substrates, some of the accumulated and methylated Hg is carried towards the streams in association with particulate matter (mineral and organic sediments) and tea-coloured dissolved organic matter (DOM): the darker and the more cloudy the water, the more Hg is available for trophic uptake in fresh waters. Basically, DOM and Hg concentrations increase in proportion with increasing wet-area coverage above each stream location, and this can be mapped, systematically.

This web site will soon display details of the Hg modelling and mapping process at the forest stand level, and how the process is applied to discerning Hg concentration patterns according to the open stream and lake sediment files compiled by the Geological Survey of Canada. The image on the left shows a selection of the Geological Survey of Canada open-file data for Hg in lake and stream sediments overlaid on a satellite image for Canada, also containing a blue shaded upland/lowland delineation.

 

Publications

Thesis Work

  • Mina Nasr. 2007. Mercury levels in fungal fruiting bodies from interior and coastal forests in the Bay of Fundy region, New Brunswick, Canada
  • Laura Sweeney2007. Mercury cycling through finfish aquaculture within the lower Bay of Fundy: possibilities for control in support of the health of coastal communities