Total dissolved mercury in the water column of several natural and artificial aquatic systems of Northern Quebec (Canada)

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Abstract
Total dissolved mercury concentrations in the water column of the La Grande-2 and Laforge-1 hydroelectric reservoirs and four neighbouring lakes near James Bay, northern Quebec, were measured to establish the impacts of extensive flooding of terrestrial environments on this potential vector of contamination to the aquatic biota. During three field visits between June and October 1993, while the sites were free from ice cover and the water column was not strongly stratified, filtered water samples were collected from multiple depths at various locations within both reservoirs and the four lakes. To compare the diverse subenvironments within the reservoir systems, sampling sites were selected to represent differences in (i) type of flooded soil, (ii) impoundment history, and (iii) water depth. At all stations total dissolved mercury concentrations were nearly constant, with an average value of 2.30 ng∙L−1 and a standard error of 0.04 ng∙L−1. Furthermore, reservoir concentrations were not statistically different from those of the lakes. Hence, we propose that the dissolved component in the water column does not play a significant role in the transfer of inorganic mercury to the aquatic food chain in recently developed hydroelectric reservoirs.