Carignan (top of page)

Lake sediments are often used to reconstruct the history of metal deposition and to determine the relative importance of human versus natural sources of pollution. However, chemical and biological reactions occurring in lake sediments (early diagenesis) can influence the vertical distribution of trace elements, and compromise the use of sediment profiles as historical records of anthropogenic pollution. This study examines the chemical behaviour and determines the post-depositional mobility of trace elements (Ag, As, Cd, Cu, Hg, Ni, Pb, Pd, Pt, Rh, Zn) in recent lake sediments of unperturbed Boreal Shield lakes exposed to high, medium or low levels of atmospheric pollution. Dated sediment cores and porewaters are analyzed for major cations and anions, sulfide, polysulfides, organic carbon and trace elements. The vertical redistribution of metals in sediments is quantified using diagenetic models. Measurements of stable Pb isotopes are used to quantify Pb sources to sediments and determine Pb availability to aquatic organisms. The study will determine in which cases sedimentary metal profiles can be interpreted as historical records of trace metal pollution from human activities. Because wildfire is a major recurring (70-100 yr) natural disturbance in the boreal forest, some lakes with known fire histories are also sampled to determine the effects of fire on metal deposition chronologies.

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Edwards (top of page)

Writing of publications from last 4 years of research data. See 2002-03 project for additional information.

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Hendershot (top of page)

The soils in areas near Cu and Zn mines are often developed on glacial sediments and bedrock that are rich in trace metals. Since metals released from this natural source could easily be confused with metals associated with anthropogenic pollution, it is important to quantify the magnitude of this source. With the collaboration of researchers at the Geological Survey of Canada (GSC: J. Percival and G. Hall) we will identify minerals or polymineralic rock fragments (sand or silt sized) that would be a source of trace metals as the material weathers. The materials thought a priori to be the most likely to release trace metals will separated for use in laboratory weathering experiments. The data obtained will be used to calibrate existing mineral weathering models that will then be used to make estimates of annual release rates of trace metals.

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Lamoureux (top of page)

• Samples from the Sudbury area will be collected using a pair of High Volume Cascade Impactors and samples will be shared among G. Spiers, J. Lu and M. Lamoureux. Before this sampling is initiated, the location of the samplers and the timing of the sampling will be discussed with personnel from the Meteorological Service of Canada (Dr. Cathy Banic).

• The concentration of Cu, Ni, Pb, Zn, and Cd in airborne particulate matter as a function of particle size will be determined from samples collected in the Sudbury area and compared with results obtained from the Rouyn-Noranda area. This comparison will help determining (1) which metals are good indicators of anthropogenic sources; and (2) which particle size range is representative of anthropogenic sources for the metals that are good indicators.

• The determination of lead isotope ratio (206Pb/207Pb) as a function of particle size from samples collected from the Sudbury area will be compared with results obtained from the Rouyn-Noranda. The smelting process in Sudbury is different from that in Rouyn-Noranda and thus the lead isotope ratio should be different and act as a fingerprint of the respective anthropogenic source. The lead isotope ratio from a sample originating from an anthropogenic source is expected to be particle size dependent since smelter processes generates predominantly small particles (e.g., less than 2 micrometers). Therefore, this would provide important information to the regulatory bodies about which size fraction is relevant when carrying lead isotope ratio determination for the purpose of fingerprinting the anthropogenic source. Therefore, the lead loading in the environment from the fingerprinted source could be determined with greater accuracy.

• Chemical speciation of Ni, Cu, and Pb using XAFS (using both XANES and EXAFS, when appropriate) will be completed for samples collected in the Rouyn-Noranda. The Ni, Cu, and Pb XAFS spectra have been collected for the 2000 and 2001 sample collection. Cu, Ni, and Pb XAFS spectra have been analyzed for the 2000 collection. Ni and Pb need to be analyzed for the 2001 collection. No more samples will be subjected to XAFS analysis in 2003-2004. Therefore, no chemical speciation comparison between Sudbury and Rouyn-Noranda samples will be possible.

• No wet event samples from the summer 2003 will be analyzed. Some samples from the summer 2002 have been analyzed using XAFS (for Ni) and results will be reported when analysis is completed.

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Lu (top of page)

This project focuses on applications of the new method we developed in 2001-02 to study the mechanisms of the mercury depletion/oxidation phenomenon that is observed in polar regions each year after polar sunrise, and to study the effects of rainwater on mercury species associated with atmospheric particulate matter/aerosols. The new method combines a temperature-programmable thermal desorption process for separating mercury species with ICP-MS for elemental detection and quantification. This method will be used to identify and quantify the mercury species produced during the polar mercury depletion/oxidation events and to monitor the changes/transformation of mercury species associated with atmospheric particulate matter/aerosols under natural environmental conditions (e.g., rain events and temperature). This information can be used to:

1. Achieve source identification and apportionment of mercury in polar ecosystems;
2. Identify the pathways and predict the mobility and availability of mercury in the environment;
3. Understand mercury depletion/conversion phenomena that are observed in the polar regions (and other places where O^₃/Hg⁰ depletion occurs) each year after polar sunrise; and
4. Understand the cycling of mercury in the environment and in assessing its risk to ecological systems and to human health.

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Palace (top of page)

This project is part of a larger ongoing study to examine the geochemical factors determining arsenic mobility in sediments that have been historically loaded with arsenic-rich gold mine tailings. Balmer Lake, the study site, is a freshwater system in Northwestern Ontario that receives treated mine tailings from 2 active gold mines (Placer Dome and GoldCorp). The project is currently examining the role of nutrients, organic carbon and redox conditions on the remobilization of arsenic from sediments to the overlying water column and resident biota. Additionally, reclamation strategies utilizing microporous mineral matrices are being examined using a series of field enclosure (limnocorral) experiments. The proposed additional portion of the project is designed to determine the potential for bacteria that reduce arsenic as part of their energy metabolism to contribute to arsenic mobilization from the sediment into the water column. Iron is the most important factor for binding arsenic in the sediments. Since the binding of arsenic is dependent on the redox state of iron, bacterial reduction of iron is also relevant and will constitute a major portion of the study.

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Spiers (top of page)

The Energy-dispersive Miniprobe Multi-element Analyzer (EMMA), in association with a micro-X-Ray Diffraction (XRD) instrument, will provide data for research projects initiated within the Sudbury Smelter Footprint to provide detailed information describing the Sudbury Fingerprint. The current MITE-RN application will provide technical and logistical support for the following projects:

1. Quantification and description of current particle emission profiles within the Sudbury smelter footprint;
2. Documentation of the particle emissions history by examination of relict smelter particle distributions in soils, sediments and peatlands of the Sudbury smelter footprint region;
3. Quantification of individual particle chemistry and mineralogy of relict smelter particles in soils, sediments and peatlands of the Sudbury smelter footprint region;
4. Analyses of selected ferns from a variety of sites of the Sudbury smelter footprint region to ascertain their abilities to hyperaccumulate potential contaminants of concern such as As, Se, Cd, Sb and Tl;
5. Quantification of the mobile solid-phase composition, mineralogy and morphology for selected Podzolic pedons on glaciofluvial sediments located along a 20 km transect NE of a regional smelter;
6. Quantification of lysimeter leachates by ICP-AES, ICP-MS, AAS or solution EMMA for selected Podzolic pedons on glaciofluvial sediments located along a 20 km transect NE of a regional smelter; and
7. Microchemical dendrological study of trees growing on glaciofluvial sediments along an impact gradient on glaciofluvial sediments located along a 20 km transect NE to examine the historical metal uptake patterns of selected deciduous and coniferous species.

The EMMA will be used to analyze a series of grains from Hendershot (Project A7) both before and after weathering experiments to ascertain whether there is incongruent dissolution of metals from any particular mineral or particle type. Selected grains will also be examined by SEM-EDS to examine any surface alteration patterns and determine the presence of secondary products. Further examination of weathered columns may be undertaken following impregnation and polishing using electron microbeam techniques if deemed appropriate. Colloidal materials on filters from soil lysimeters installed along an impact gradient in Project B1 will also be analyzed for elemental composition using the EMMA, as well as for mineralogical and morphological information by a combination of micro-XRD and SEM-EDS.

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