A test of the integrity of metal records in sediment cores based on the documented history of metal contamination in Lac Dufault (Québec, Canada) (original) (raw)
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Chemical Geology, 2015
Iron mining in Schefferville (1939-1977) in subarctic Quebec has left behind large numbers and quantities of tailing deposits. The impact of past mining activity on aquatic ecosystems in the Schefferville area has been studied using geochemical and isotopic (Pb, Zn and Fe) analyses of lake sediments, ore deposits, tailings and epiphytic lichens. Analysis of two sediment cores from Lakes Dauriat and Oksana reveals that the surface geochemical cycle of the Schefferville area has been profoundly disturbed by anthropogenic activity such as mining. Disturbances were particularly abrupt at the transitions from pre-mining to mining and mining to post-mining periods. Elemental and isotopic analyses of the lake sediments reveal four different end-member contributions to the lake sedimentation, with changes in terms of sources and source contribution observed throughout the sedimentation history. End-members were identified using Pb, Zn and Fe isotopes and are consistent for each element. Lead isotope ratios vary from highly radiogenic (206 Pb/ 204 Pb = 27) to less radiogenic (206 Pb/ 204 Pb = 17.7) from the bottom to the top of the sediment cores. Iron isotope compositions vary from −0.2‰ to 1‰, the latter value remaining constant throughout the sedimentary history of Lake Oksana. A systematic difference in the Zn isotope ratios of the two lakes is also observed, and can be explained by local differences in basin lithology. In order to identify pollution sources, samples from ores and tailings and epiphytic lichens were measured as proxies of mining activity, lithology, and atmospheric deposition, respectively. The impact of anthropogenic activity is clearly evident in the sediment records and results from mining activity, as well as local urban and industrial activities (waste water inputs). Long-range atmospheric deposition also accounts for some of the variations in isotopic composition measured in the sediments. The systematic coupling of Pb isotopes with Zn or Fe isotopes allows us to identify and constrain the metal sources that contributed to sediment contamination. This study demonstrates that disturbance due to mining activities is very effective in rapidly modifying lake sediment composition. Though the disturbances remained local in terms of geographic extent, the damage to the aquatic ecosystem has been significant and may persist for decades.
Temporal and spatial trends in metal loads to sediments of Lake Simcoe, Ontario
Water, Air, & Soil Pollution, 1988
Metal loads to sediments of Lake Simcoe were partitioned into three components, which were attributable to natural background, accelerated erosion, and point + atmospheric sources. These loads were calculated over time using metal concentration profiles together with pre-setttement sedimentation rates based on sonar and time-variable sedimentation rates based on 21°Po profiles in cores. Concentrations of metals significantly higher than pre-settlement concentrations were observed in all cores in the case of Pb, back to 80 yr BP on average, and in at least 75 % of cores, back to 60 yr BP for Cd and Zn and 30 to 45 yr BP for Cu, Ni, and Cr. Total metal loads increased 3 x for Cu and Ni, 4 x for Zn and Cr, 11 x for Cd and nearly 20 x for Pb from pre-1800 to 0 to 10 yr BP. At present about 90% of the anthropogenic loads of Pb and Cd, and 60 to 70}0 of the anthropogenic Cu, Ni, Zn, and Cr, are from point + atmospheric sources, the balance being from increased erosion. The direct atmospheric input of Cd is relatively high, approximately 77% of point + atmospheric inputs, while inputs of Cr and Ni are low at 1% and 9%, and inputs of Cu, Zn, and Pb are intermediate at 20 to 40% of point + atmospheric inputs. Two significant findings on spatial distribution of metals were the large increases in metal loads to Cook Bay following the drainage of 33 km 2 of marshes for agricultural use and the widespread dispersal of Cr from point source(s) in Kempenfelt Bay.
Sediment trace metal profiles in lakes of Killarney Park, Canada
Environmental Pollution, 2004
The lakes in Killarney Provincial Park (KPP) located 40e60 km southwest of Sudbury, Ontario are beginning to recover after decades of being severely affected by acidification and atmospheric pollutants. Detailed profiles of acid-recoverable trace elements (As. Cd, Cu, Co. Fe, Mn, Ni, Pb and Zn) were obtained after aqua regia digestion and ICP-OES analysis of sediment cores taken from six Park lakes. Results permitted the identification of two types of profiles. The first type applies to elements such as Fe, Mn, As and Co for which historical deposition and recent recovery are strongly masked by diagenetic remobilization. The second type of profile applies to elements such as Cd, Cu, Ni, Pb and Zn on which the history of industrialisation in North America and mining activities in Sudbury can be superimposed. Based on sediment data of trace elements less affected by diagenetic remobilization (Cd, Cu, Ni, Pb, Zn), chemical recovery indices can be estimated from depth profiles. Indices of maximum (C p ) and surface (C s ) contamination were calculated by dividing the concentration of a given metal by the pre-industrial level. The ratio of the two indices provided a simple estimation of the chemical recovery of lakes that does not consider the influence of the watershed or the lake pH. Profiles of metals in sediment of KPP complement the water quality monitoring data and tend to indicate that this area is in transition from dominant influence of regional pollution sources to becoming controlled by continental atmospheric deposition.
Water, Air, and Soil Pollution, 2006
Mining operations at Mårsätter in 1877-81 resulted in increased metal loading to a small lake, notably as sulphidic tailings. The event is taken as an opportunity to study the present environmental impact of a historical single major metal release. Lake water and four sediment cores were sampled and analysed for principal and trace elements in solid and aqueous phases as well as general hydrochemical conditions. Chronologies were determined from 206 Pb/ 207 Pb ratios and historical records.
Water, Air, & Soil Pollution, 2000
Sediment cores were collected from six lakes (Moose, Stuart, Chilko, Kamloops, Nicola and Harrison Lakes) distributed throughout the Fraser River Basin, British Columbia. The cores were dated primarily from 210 Pb profiles and dating was corroborated by counting laminae and by using 137 Cs as a discrete time marker. The cores were analyzed for a suite of metals (Co, Cr, Cu, Hg, Ni, Mn, Pb and Zn) and organic carbon. The data were evaluated in the context of post-1900 contamination by metals in the Fraser River basin. Overall, lake sediments from the Fraser Basin remain relatively pristine in terms of metal contamination, exhibiting only minor metal enrichments in layers dating from industrial times (post-1900). Stuart Lake, which received Hg contamination from a mine on Pinchi Lake, shows a clear contaminant Hg signal. Pb exhibits ubiquitous contamination in five of the six lakes studied. The Pb enrichments are minor (ranging from 8.4 to 30.9 µg g −1) and consistent with local automotive emissions from the use of leaded gasoline possibly augmented by long-range transport from industrial and municipal centers along the west coast. The largest Pb fluxes were observed in Kamloops, Moose and Harrison Lakes, each of which has either a highway or a large urban centre as a local source of Pb. This watershed-scale evaluation offers a unique opportunity to compare the relative importance of local and regional sources of contamination.
Minerals
The contamination of aquatic sediments by metals is a worldwide phenomenon and its assessment is a fairly complex issue, as numerous factors affect the distribution of particular contaminants in the environment, as well as their bioavailability. Wigry Lake, as the object of this study, is almost a perfect water body for such considerations. It has been well investigated and densely sampled (up to 459 sediment samples). The quantities of seven metals were determined using the atomic absorption spectrometry (AAS) or inductively coupled plasma (ICP)-MS methods, following previous extraction in a microwave oven. The levels of concentration of the examined elements were as follows (min–max (mg·kg−1)): Cd—0.003–3.060; Cr—0.20–22.61; Cu—0.02–59.70; Fe—80–32,857; Mn—18–1698; Pb—7.0–107.5; Zn—3.1–632.1. Significant differences were also registered in terms of particular metal concentrations in different sediment types found at the lake bottom. Five different geochemical backgrounds and sedim...
Stratigraphy of total metals in PIRLA sediment cores
Journal of Paleolimnology, 1992
Sediment cores from 30 low-alkalinity lakes in northern New England (NE), New York (NY), the northern Great Lakes States (NGLS) of Minnesota, Michigan, and Wisconsin, and Florida (FL) have been dated by 21~ and analyzed for water and organic content, eight major elements (A1, Ti, Fe, Mn, Ca, Mg, Na, K) plus four trace metals (Pb, Zn, Cu, and V). Variations in the percentages of major elements through time are dominated by long-term independent variations in the abundance of SiO2, FeO, and to a lesser extent Ca and A1. Additional variations are caused by varying proportions of inorganic matter. Major variations in chemistry are generally unrelated to documented disturbances in the watersheds; most disturbances are minor fires or selective logging.
On metal diagenesis in contaminated sediments of the Deûle river (northern France)
Applied Geochemistry, 2010
The objective of the present work was to assess depth-related variations in the (bio)geochemical processes involved in anoxic sediments from the Deûle river, and to examine particularly their impacts on the distribution of anthropogenically sourced metals. Anoxic sediment samples were sliced and analyzed to determine total concentrations vs. depth of elements and corresponding pore waters were analyzed to determine concentration profiles with depth of pH, Eh, alkalinity, O 2 , dissolved organic carbon (DOC), and main inorganic anions and cations present in the medium. It was shown that rapid depletions of O 2 , NO À 3 and SO 2À 4 , accompanied with HCO À 3 generation and a sharp decrease in the redox potential occurred within the first centimeters of the surface sediment as a consequence of early diagenesis. Bacterial reductive dissolution of Mn(III and IV) and Fe(III) oxides/hydroxides to Mn(II) and Fe(II) accompanied by microbial degradation of organic matter took place as well, and resulted in trace metal increases in the pore water at levels that raised the possibility of mineral generation. Thermodynamic calculations predicted removal of metals from interstitial waters through combinations with carbonates and/or sulfides. These took place either by direct precipitation to form pure crystals, or by coprecipitation/sorption with/ into calcite and with pyritic compounds. Chemical sequential extraction data were useful in this work to support, at least partially, some thermodynamic predictions concerning the existence of interactions between trace metals and carbonate and sulfide ions to generate (co)precipitates. Electron paramagnetic resonance (EPR) studies on Deûle sediments revealed the presence of Mn(II) adsorbed onto sedimentary calcite surfaces. X-ray diffractograms of heavy minerals from Deûle sediments extracted with CHBr 3 by density separation exhibited peaks ascribed to galena, sphalerite and pyrite. In addition to these compounds, using a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectrometer (EDS), micro-analyses of sedimentary heavy minerals confirmed successfully the existence of other thermodynamically predicted associations: covellite; chalcopyrite, greenockite and/or amorphous CdS.
A 157-cm-long sediment core from Longemer Lake in the Vosges Mountains of France spans the past two millennia and was analyzed for trace metal content and lead isotope composition. Trace metal accumulation rates highlight three main input phases: Roman Times (cal. 100 BC–AD 400), the Middle Ages (cal. AD 1000–1500), and the twentieth century. Atmospheric contamination displays a pattern that is similar to that seen in peat bogs from the region, at least until the eighteenth century. Thereafter, the lake sediment record is more precise than peat records. Some regional mining activity, such as that in archaeologically identified eighteenth-century mining districts, was detected from the lead isotope composition of sediment samples. Composi-tional data analysis, using six trace metals (silver, arsenic, cadmium, copper, lead and zinc), enabled us to distinguish between background conditions, periods of mining, and of other anthropogenic trace metal emissions, such as the recent use of leaded gasoline.().,-volV) (0123456789().,-volV)
Journal of Paleolimnology, 2008
Qualitative and quantitative analysis of fossil diatoms and geochemical signals preserved in the sediments of Lac Dauriat (subarctic Quebec) were performed to evaluate the impacts of nearby mining activity and the expansion of the town of Schefferville on the water quality of the lake, and to reconstruct the changes of its trophic status. The presence of taxa typical of nutrient-enriched environments (e.g., Cyclostephanos invisitatus, Nitzschia gracilis, Nitzschia perminuta) and the low percentages of chrysophytes were indicative of the advanced state of eutrophication of the lake during the peak of mining activity, and were evidence of the negative impacts of municipal waste on the water quality of Lac Dauriat. Sedimentary analysis of metals, notably lead, mercury, cadmium, bismuth, cobalt, copper and zinc, showed maximum concentrations between 1940 and 1960 with mining era to predevelopment enrichment factors ranging from 4.5 to 7.9. The changes seen in recent sediments reflected 3 distinct stages in the recent history of this ecosystem: (a) the non-perturbed, pre-mining , (b) the perturbed, mining period with accelerated eutrophication, and (c) the post-mining period with indications of natural recovery of the system after the installation of a water treatment plant in 1975, the closing of the mine in 1983, and the subsequent exodus of the town's population. Despite the trajectory towards a return to the lake's natural conditions, water resource managers and (paleo-) limnologists should be alarmed that the impacts of past human disturbance are still in evidence more than 20 years after the closure of the mines, and that Lac Dauriat has yet to reach its natural state of the period preceding extreme anthropogenic impact.