Anthropogenic mercury enrichment in remote lakes of northern Qu�bec (Canada) (original) (raw)
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Environmental Science & Technology, 2009
Recent and historical deposition of mercury (Hg) was examined over a broad geographic area from southwestern Northwest Territories to Labrador and from the U.S. Northeast to northern Ellesmere Island using dated sediment cores from 50 lakes (18 in midlatitudes (41-50°N), 14 subarctic (51-64°N) and 18 in the Arctic (65-83°N)). Distinct increases of Hg over time were observed in 76% of Arctic, 86% of subarctic and 100% of midlatitude cores. Subsurface maxima in Hg depositional fluxes (µg m-2 y-1) were observed in only 28% of midlatitude lakes and 18% of arctic lakes, indicating little recent reduction of inputs. Anthropogenic Hg fluxes adjusted for sediment focusing and changes in sedimentation rates (∆F adj,F) ranged from-22.9 to 61 µg m-2 y-1 and were negatively correlated (r)-0.57, P < 0.001) with latitude. Hg flux ratios (FRs; post-1990)/pre-1850) ranged from 0.5 to 7.7. The latitudinal trend for Hg ∆F adj,F values showed excellent agreement with predictions of the global mercury model, GRAHM for the geographic location of each lake (r) 0.933, P < 0.001). The results are consistent with a scenario of slow atmospheric oxidation of mercury, and slow deposition of reactive mercury emissions, declining with increasing latitude away from emission sources in the midlatitudes, and support the view that there are significant anthropogenic Hg inputs in the Arctic.
Environmental Pollution, 2013
Spatial and temporal changes in mercury (Hg) concentrations and organic carbon in lake sediments were examined from the Hudson Bay Lowlands to investigate whether Hg deposition to sediments is related to indicators of autochthonous production. Total organic carbon, "S2" carbon (mainly algalderived OC), C:N and v 13 C indicators suggest an increase in autochthonous productivity in recent decades. Up-core profiles of S2 concentrations and fluxes were significantly correlated with Hg suggesting that varying algal matter scavenging of Hg from the water column may play an important role in the temporal profiles of Hg throughout the sediment cores. Absence of significant relationship between total Hg and methyl Hg (MeHg) in surficial sediments suggested that inorganic Hg supply does not limit MeHg production. MeHg and OC were highly correlated across lakes in surface and deep sediment layers, indicating that sediment organic matter content explains part of the spatial variation in MeHg concentrations between lakes.
Natural and Anthropogenic Mercury Distribution in Marine Sediments from Hudson Bay, Canada
Environmental Science & Technology, 2010
Twelve marine sediment cores from Hudson Bay, Canada, were collected to investigate the response of sub-Arctic marine sediments to atmospherically transported anthropogenic mercury (Hg). Modeling by a two-layer sediment mixing model suggests that the historical Hg deposition to most of the sediment cores reflects the known history of atmospheric Hg deposition in North America, with an onset of increasing anthropogenic Hg emissions in the late 1800s and early 1900s and a reduction of Hg deposition in the mid-to late-1900s. However, although anthropogenic Hg has contributed to a ubiquitous increase in Hg concentrations in sediments over the industrial era, the most elevated industrial-era sedimentary Hg concentrations only marginally exceed the upper preindustrial sedimentary Hg concentrations. Analysis of δ 13 C and relationship between Hg and organic matter capture suggests that the response of Hudson Bay sediments to changes in atmospheric Hg emissions is largely controlled by the particle flux in the system and that natural changes in organic matter composition and dynamics can cause variation in sedimentary Hg concentrations at least to the same extent as those caused by increasing anthropogenic Hg emissions.
Water, Air, & Soil Pollution, 1995
An ongoing problem in evaluating the significance of mercury (Hg) in surficial materials is distinguishing sources of natural (spatial) variation of the geological/geochemical environment from sources (airborne, waterborne, etc.) of anthropogenic (temporal) variation. The Geological Survey of Canada (GSC) has carried out a series of sampling programs, including one in the southeastern part of the geologically complex Canadian Shield, in order to link the easily observable lithological variations of bedrock with the chemical composition of overlying glacial deposits and lake sediments. This research aims to provide a base against which observed variations in life systems can be judged as natural or anthropogenic. In the study area, high concentrations of Hg and other trace elements in lake sediment and glacial sediments can be related to glacial dispersal from mineralized bedrock and/or bedrock with high natural background concentrations of these elements.
Spatiotemporal patterns of mercury accumulation in lake sediments of western North America
The Science of the total environment, 2016
For the Western North America Mercury Synthesis, we compiled mercury records from 165 dated sediment cores from 138 natural lakes across western North America. Lake sediments are accepted as faithful recorders of historical mercury accumulation rates, and regional and sub-regional temporal and spatial trends were analyzed with descriptive and inferential statistics. Mercury accumulation rates in sediments have increased, on average, four times (4×) from 1850 to 2000 and continue to increase by approximately 0.2μg/m(2) per year. Lakes with the greatest increases were influenced by the Flin Flon smelter, followed by lakes directly affected by mining and wastewater discharges. Of lakes not directly affected by point sources, there is a clear separation in mercury accumulation rates between lakes with no/little watershed development and lakes with extensive watershed development for agricultural and/or residential purposes. Lakes in the latter group exhibited a sharp increase in mercury...
Mercury in lake sediments of the Precambrian Shield near Huntsville, Ontario, Canada
Environmental Geology, 1998
Long sediment cores (1 1 m) were collected from eight Precambrian Shield lakes in southern Ontario, Canada and analyzed for mercury (Hg), loss-on-ignition (LOI), and a suite of 36 other elements. Results indicated at least 100-fold variation in sediment Hg concentrations between lakes in close proximity (from 450 ppb), comparable to the variation reported for lakes across the whole of Canada. Strong areal correlations between Hg concentrations and LOI (r 2 p0.77), between Hg and other trace element concentrations (Pb, Zn, Cd, Sb, As, Br), and similarities in the vertical concentration profiles of Hg and LOI, all point to the importance of organic matter in the release, transport and redistribution of metals in watershed systems. The spatial pattern of Hg concentrations in deep, precolonial sediments (1 20 cm) was found to mirror the pattern of Hg concentrations in modern surface sediments, an observation that was confirmed in a follow-up survey (r 2 p0.85; np25 lakes), indicating that natural processes govern the unequal distribution of Hg among these lakes. Between-lake differences in surface sediment Hg concentrations normalized to organic carbon (Hg/C) were also reflected by Hg concentrations in smallmouth bass normalized to 35 cm length (R 2 p0.63; np15 lakes). The latter relationship suggests that smallmouth bass and lake sediment indicators provide mutually supportive information regarding Hg loading to the lacustrine environment from geological sources in the watershed system.
Environmental Science & Technology, 2002
Mercury (Hg) contamination of aquatic ecosystems and subsequent methylmercury bioaccumulation are significant environmental problems of global extent. At regional to global scales, the primary mechanism of Hg contamination is atmospheric Hg transport. Thus, a better understanding of the long-term history of atmospheric Hg cycling and quantification of the sources is critical for assessing the regional and global impact of anthropogenic Hg emissions. Ice cores collected from the Upper Fremont Glacier (UFG), Wyoming, contain a high-resolution record of total atmospheric Hg deposition (ca. 1720-1993). Total Hg in 97 ice-core samples was determined with trace-metal clean handling methods and low-level analytical procedures to reconstruct the first and most comprehensive atmospheric Hg deposition record of its kind yet available from North America. The record indicates major atmospheric releases of both natural and anthropogenic Hg from regional and global sources. Integrated over the past 270-year ice-core history, anthropogenic inputs contributed 52%, volcanic events 6%, and background sources 42%. More significantly, during the last 100 years, anthropogenic sources contributed 70% of the total Hg input. Unlike the 2-7-fold increase observed from preindustrial times (before 1840) to the mid-1980s in sediment-core records, the UFG record indicates a 20-fold increase for the same period. The sediment-core records, however, are in agreement with the last 10 years of this ice-core record, indicating declines in atmospheric Hg deposition.
Environmental Science & Technology, 2008
The purpose of the METAALICUS experiment was to examine the timing and magnitude of the response of fish Hg concentrations to changes in atmospheric Hg loading. Enriched stable Hg isotopes were applied as HgNO 3 to the lake (202 Hg), wetland (198 Hg) and upland (200 Hg) compartments of the L658 watershed at ~22 ug m-2 yr-1 since 2001 (1, 2). However, the present study focused on deposition of ambient Hg, not the experimentally-applied isotopic Hg. Analytical Methods Precipitation and throughfall samples collected between 1992 and 2000 were analysed for total Hg (THg; all forms of Hg in a sample) using EPA Method 1631 (3) by Flett Research Ltd. (Winnipeg, MB). Briefly, all Hg in samples was oxidized to Hg(II) by the addition of BrCl, reduced to Hg(0) using SnCl 2 , purged onto gold traps, thermally desorbed and analyzed by cold vapour atomic fluorescence spectrometry (CVAFS). Samples collected in the METAALICUS watershed between 2001 and 2006 were analysed using inductively coupled plasma mass spectrometry (ICP-MS, 4, 5). Because ICP-MS quantifies concentrations of individual Hg isotopes, it was possible to distinguish concentrations of ambient Hg from the experimentally loaded enriched Hg isotopes. To calculate concentrations of ambient Hg, an isotope that was not experimentally applied to the watershed was used as an ambient Hg surrogate (199 Hg). Samples collected in 2001-2004 were analyzed at the Trent University Worsfold Water Quality Center (Peterborough, ON). Samples were continuously mixed in-line with SnCl 2 using peristaltic pumps, and the reduced gaseous Hg(0) formed was separated in a custom-made gas/liquid separator and swept into the plasma of a Finnigan Element 2 ICP-MS (6). For samples collected between 2005 and 2006, analysis was completed at the University of Alberta Biogeochemical Laboratory (Edmonton, AB). In this laboratory, reduction of Hg and gas/liquid separation was accomplished using an automated Tekran 2600 total Hg analyzer interfaced with a PerkinElmer Elan DRC-e ICP-MS for detection. Precipitation and throughfall samples collected for methylmercury (MeHg) analyses prior to 2001 were distilled, ethylated by additions of sodium tetra-ethyl-borate (NaBEt 4), and volatile Hg species were purged and trapped using either carbo or tenax traps. Samples were thermally desorbed and separated by gas chromatography before quantification by CVAFS (7, 8). Samples collected in the METAALICUS watershed were analyzed for MeHg as described above, except that