Agnès Grondin - Academia.edu (original) (raw)

Papers by Agnès Grondin

Water, Air, & Soil Pollution, 1995

In a sub-Arctic region of the province of Quebec, at sites situated 200 to 1400 km away from the ... more In a sub-Arctic region of the province of Quebec, at sites situated 200 to 1400 km away from the closest industrial centers, we find the ubiquitous presence of anthropogenic Hg, reflected by steadily increasing concentrations of this metal in lake sediments, since about 1940, to rates averaging 2.3 times the preindustrial levels. Mercury concentrations in lake sediments were found to be proportional to the amounts of telTestrial organic carbon from the catchment area. It would, therefore, be misleading to derive continental-scale gradients of this pollutant based on Hg concentrations in oligotropbic lake sediments, unless they are normalized to their organic carbon content. Our normalized data for sediments of remote lakes along a 1200 km transect (45 to 55~ clearly indicate that the distribution pattern of long-range Hg contamination is independent of the latitude over the boreal forest domain. This uniform contamination contrasts with that of Pb, which decreases towards the north over the same latitudinal span, away from the industrial centers of the St Lawrence Valley and the U.S. Mid-West.

Canadian Journal of Fisheries and Aquatic Sciences, 1995

Forest soils and their flooded equivalents were sampled in the Cabonga (southern Quebec) and La G... more Forest soils and their flooded equivalents were sampled in the Cabonga (southern Quebec) and La Grande (northern Quebec) hydroelectric complexes and analyzed at 1-cm intervals for organic C, N, Fey Mn, Ng, and Pb. In the La Grande region, thin Clhzdina sp. podzols and thicker Pleur~ziurn sp. podzols are characterized by lower Hg burdens (2500 and 5100 pg.m-L, respectively) than the thicker but less dense soils typical of wetter environments (6000 to 8000 pgmm-2). These differences suggest that a fraction of Hg is leached downslope from uplands (podzols) and partially accumulates in poorly drained soils (wetlands) below. Unlike Pb, Hg showed no apparent decrease in atmospheric transport over 1000 km from south to north, away from the industrialized regions, Upon inundation, the oxidation-reduction potential drops rapidly but there was no noticeable decrease in the organic C burden, with the exception of flooded podzsls where the surficial organic layer may undergo erosion. In Wooded wetland soils, Hg, Pb, and Fe display a partial redistx-ibution towards the sediment-water interface, but the Hg burdens of these soils remain comparable to those of their unflooded equivalents. In contrast, the surficial erosion of the flooded podzols may represent one pathway for Hg to enter organisms in the reservoir.

Water, Air, & Soil Pollution, 1995

In a sub-Arctic region of the province of Quebec, at sites situated 200 to 1400 km away from the ... more In a sub-Arctic region of the province of Quebec, at sites situated 200 to 1400 km away from the closest industrial centers, we find the ubiquitous presence of anthropogenic Hg, reflected by steadily increasing concentrations of this metal in lake sediments, since about 1940, to rates averaging 2.3 times the preindustrial levels. Mercury concentrations in lake sediments were found to be proportional to the amounts of telTestrial organic carbon from the catchment area. It would, therefore, be misleading to derive continental-scale gradients of this pollutant based on Hg concentrations in oligotropbic lake sediments, unless they are normalized to their organic carbon content. Our normalized data for sediments of remote lakes along a 1200 km transect (45 to 55~ clearly indicate that the distribution pattern of long-range Hg contamination is independent of the latitude over the boreal forest domain. This uniform contamination contrasts with that of Pb, which decreases towards the north over the same latitudinal span, away from the industrial centers of the St Lawrence Valley and the U.S. Mid-West.

Canadian Journal of Fisheries and Aquatic Sciences, 1995

Forest soils and their flooded equivalents were sampled in the Cabonga (southern Quebec) and La G... more Forest soils and their flooded equivalents were sampled in the Cabonga (southern Quebec) and La Grande (northern Quebec) hydroelectric complexes and analyzed at 1-cm intervals for organic C, N, Fey Mn, Ng, and Pb. In the La Grande region, thin Clhzdina sp. podzols and thicker Pleur~ziurn sp. podzols are characterized by lower Hg burdens (2500 and 5100 pg.m-L, respectively) than the thicker but less dense soils typical of wetter environments (6000 to 8000 pgmm-2). These differences suggest that a fraction of Hg is leached downslope from uplands (podzols) and partially accumulates in poorly drained soils (wetlands) below. Unlike Pb, Hg showed no apparent decrease in atmospheric transport over 1000 km from south to north, away from the industrialized regions, Upon inundation, the oxidation-reduction potential drops rapidly but there was no noticeable decrease in the organic C burden, with the exception of flooded podzsls where the surficial organic layer may undergo erosion. In Wooded wetland soils, Hg, Pb, and Fe display a partial redistx-ibution towards the sediment-water interface, but the Hg burdens of these soils remain comparable to those of their unflooded equivalents. In contrast, the surficial erosion of the flooded podzols may represent one pathway for Hg to enter organisms in the reservoir.