Chetelat J.,Environment Canada |
Amyot M.,University of Montreal |
Arp P.,University of New Brunswick |
Blais J.M.,University of Ottawa |
And 17 more authors.
Science of the Total Environment | Year: 2014
The Canadian Arctic has vast freshwater resources, and fish are important in the diet of many Northerners. Mercury is a contaminant of concern because of its potential toxicity and elevated bioaccumulation in some fish populations. Over the last decade, significant advances have been made in characterizing the cycling and fate of mercury in these freshwater environments. Large amounts of new data on concentrations, speciation and fluxes of Hg are provided and summarized for water and sediment, which were virtually absent for the Canadian Arctic a decade ago. The biogeochemical processes that control the speciation of mercury remain poorly resolved, including the sites and controls of methylmercury production. Food web studies have examined the roles of Hg uptake, trophic transfer, and diet for Hg bioaccumulation in fish, and, in particular, advances have been made in identifying determinants of mercury levels in lake-dwelling and sea-run forms of Arctic char. In a comparison of common freshwater fish species that were sampled across the Canadian Arctic between 2002 and 2009, no geographic patterns or regional hotspots were evident. Over the last two to four decades, Hg concentrations have increased in some monitored populations of fish in the Mackenzie River Basin while other populations from the Yukon and Nunavut showed no change or a slight decline. The different Hg trends indicate that the drivers of temporal change may be regional or habitat-specific. The Canadian Arctic is undergoing profound environmental change, and preliminary evidence suggests that it may be impacting the cycling and bioaccumulation of mercury. Further research is needed to investigate climate change impacts on the Hg cycle as well as biogeochemical controls of methylmercury production and the processes leading to increasing Hg levels in some fish populations in the Canadian Arctic. Crown Copyright © 2014.
Zdanowicz C.,Uppsala University |
Kruemmel E.,Inuit Circumpolar Council of Canada |
Lean D.,Lean Environmental |
Poulain A.,University of Ottawa |
And 4 more authors.
Science of the Total Environment | Year: 2014
Sulfate (SO4 2 -) and mercury (Hg) are airborne pollutants transported to the Arctic where they can affect properties of the atmosphere and the health of marine or terrestrial ecosystems. Detecting trends in Arctic Hg pollution is challenging because of the short period of direct observations, particularly of actual deposition. Here, we present an updated proxy record of atmospheric SO4 2 - and a new 40-year record of total Hg (THg) and monomethyl Hg (MeHg) deposition developed from a firn core (P2010) drilled from Penny Ice Cap, Baffin Island, Canada. The updated P2010 record shows stable mean SO4 2 - levels over the past 40 years, which is inconsistent with observations of declining atmospheric SO4 2 - or snow acidity in the Arctic during the same period. A sharp THg enhancement in the P2010 core ca 1991 is tentatively attributed to the fallout from the eruption of the Icelandic volcano Hekla. Although MeHg accumulation on Penny Ice Cap had remained constant since 1970, THg accumulation increased after the 1980s. This increase is not easily explained by changes in snow accumulation, marine aerosol inputs or air mass trajectories; however, a causal link may exist with the declining sea-ice cover conditions in the Baffin Bay sector. The ratio of THg accumulation between pre-industrial times (reconstructed from archived ice cores) and the modern industrial era is estimated at between 4- and 16-fold, which is consistent with estimates from Arctic lake sediment cores. The new P2010 THg record is the first of its kind developed from the Baffin Island region of the eastern Canadian Arctic and one of very few such records presently available in the Arctic. As such, it may help to bridge the knowledge gap linking direct observation of gaseous Hg in the Arctic atmosphere and actual net deposition and accumulation in various terrestrial media. © 2014 Elsevier B.V. All rights reserved.
Ethier A.L.M.,CRL Energy Ltd. |
Atkinson J.F.,Jarvis |
Depinto J.V.,Limno Technology |
Lean D.R.S.,Lean Environmental
Environmental Pollution | Year: 2012
The HERMES model-predicted Hg concentrations and fluxes in Lake Ontario were based on twelve lake and drainage basin variables (i.e., water temperature, precipitation rate, air Hg, surface area, mean depth, water volume, water inflow rate, inflow water Hg, inflow and lake suspended particulate matter, air-water and water-air mass transfer coefficients, and sedimentation rate). The HERMES model-predicted Hg water and surface sediment concentrations were found to be significantly correlated (±20%) with measured values (r 2 = 0.94, p < 0.0001, n = 13) and mechanistic model predictions (LOTOX2-Hg, r 2 = 0.95, p < 0.0001, n = 10). The predictive capacity of HERMES was previously tested on smaller (≤1 km 2) lakes in Nova Scotia and Ontario, Canada (i.e., water and sediment Hg concentrations were ±15% of measured data). Results suggest that HERMES could be applicable to a broad range of lake sizes. Uncertainty analyses on HERMES model input variables indicated a larger atmospheric Hg contribution for Lake Ontario when compared to previous predictions for smaller lakes. © 2011 Elsevier Ltd. All rights reserved.
Zdanowicz C.,Geological Survey of Canada |
Krummel E.M.,Inuit Circumpolar Council of Canada |
Lean D.,Lean Environmental |
Poulain A.J.,University of Ottawa |
And 3 more authors.
Geochimica et Cosmochimica Acta | Year: 2013
Part of the mercury (Hg) entering Arctic ecosystems is believed to be delivered from the atmosphere in snow but this source is difficult to quantify due to limited spatial coverage of Hg data in snow. Here we evaluate the atmospheric deposition, storage and release of total Hg (THg) and monomethyl mercury (MeHg) on Penny ice cap, Baffin Island. This is the first such study in the Baffin region. THg levels in snow and firn (mean=0.61ngL-1) are comparable to those on High Arctic glaciers but MeHg levels are noticeably higher (mean=0.11ngL-1). We find little evidence of springtime enhancement of Hg deposition in snow attributable to atmospheric mercury depletion events. Estimated accumulation rates of THg and MeHg in firn are ∼0.33 and 0.03μgm-2a-1, higher than on High Arctic glaciers, possibly due to higher precipitation on southern Baffin Island. The estimated net annual release of THg by glacial snow and ice melt is small (THg: 1.86kg; MeHg: 0.18kg). In the study area, geogenic Hg contributions from sediment-loaded glacial meltwater could be as large or larger than those from melting ice. MeHg levels are very low in meltwater-fed streams and lakes (≤0.01ngL-1), suggesting that MeHg is released early in the snowmelt season and/or quickly removed from meltwater by various processes. Summer melt and percolation on Penny ice cap remobilise Hg in firn after deposition, and this imposes resolution limits of at least 3years on depositional trends inferred from ice cores. © 2012.
Fathi M.,University of Ottawa |
Ridal J.J.,St Lawrence River Institute Of Environmental Science |
Lean D.R.S.,Lean Environmental |
Blais J.M.,University of Ottawa
Journal of Great Lakes Research | Year: 2013
The St. Lawrence River near Cornwall Ontario is affected by industrial mercury contamination of sediments and biota. It has been suggested that pulp and paper mill effluents may stimulate bacterial mercury methylation in these sediments, leading to contamination of aquatic biota. To test this hypothesis, we examined sediment-porewater dynamics of total mercury (THg) and methyl mercury (MeHg) at a site with high concentrations of wood fibers from a pulp and paper mill effluent and a nearby reference site with low wood fiber content. Dissolved phase THg (THgdiss) and MeHg (MeHgdiss) in porewater profiles showed that 38±30.9% (SD) of THg in porewaters was in the methylated form regardless of wood fiber content. MeHgdiss and THgdiss concentrations were homogeneous between porewater and overlying water, indicating (a) that there is minimal net diffusion of MeHgdiss and THgdiss and (b) that redox-dependent processes such as sulfate reduction and Fe reduction were not associated with MeHgdiss distribution in these sediment profiles. MeHg and THg in solid phase showed coincident subsurface peaks at depths>40cm suggesting either that historical deposits of MeHg on particles (MeHg(p)) are preserved in deep sediments, or that Hg methylation is active in deep sediments. © 2013 International Association for Great Lakes Research.