Sources Platform Abstracts
2001, A Yukon Odyssey: Metals on Particulates and Gaseous Mercury Fluxes
G.C. Edwards,1 P.E. Rasmussen, W.H. Schroeder, G.M. Dias1, S. Ausma1, G. Dharwarkar1, A. Steffen, P. Hazlewood
1 School of Engineering,
University of Guelph, Guelph, ON
2 Health Canada, Ottawa, ON
3 Meteorological Service of Canada, Downsview, ON
Measurements of gaseous mercury and metals on particulates were undertaken at a remote site in the Selwyn Basin, Yukon, from July 7 to August 2, 2001, to determine the source terms for metals from natural sources. This area represents a remote mercuriferous shale. Continuous mercury flux measurements were undertaken using a dynamic chamber and an aerodynamic gradient micrometeorological technique, coupled with a Tekran analyzer for measuring gaseous elemental mercury concentrations. Micrometeorological measurements were made only on the cleared shale, while the chamber method was used to measure over the shale as well as over vegetation overlying the shale. Particulate measurements were undertaken using filter packs, PIXE cascade impactors, mercury particulate traps and a total suspended particulate analyzer. The experimental Design allowed collection of particulate for various wind directions.
Chamber and MM average fluxes were similar over the measurement period (9 and 7 ng m-3 s-1, respectively, for a shale substrate concentration of 350 +/- 116 ppb). Fluxes for vegetated surfaces and a higher substrate site, along with environmental data will be presented.
Particulate matter concentrations were low at the Yukon site except during a dry period where they reached values as high as 2700 g/m3 for PM2.5 and 17,000 g/m3 for PM10. Particulate mercury concentrations (not blank corrected) averaged 10 pg/m3. Highest particulate concentrations were obtained from the south under stable conditions and from the north under unstable atmospheric conditions.
A review of the methods being used to source apportion the particulates at these natural remote sites will be made with specific reference to the experience gained thus far in the analysis of 2 sets of field data collected in 2000. To date, we have used elemental gradients, enrichment factors, correlation coefficients and elemental composition by size fraction as techniques to determine locally-derived versus non-local sources of particulates collected. We will present the latest analysis using multivariate and other statistical techniques to further validate our conclusions on particulate sources.
In situ solid state chemical speciation of some metal pollutants associated with atmospheric particulate matter of varying size.
Lamoureux, M.1, N. Warner1, J. Samson1, V. MacKinnon1, K. Lantz1, Terry Gordon1, G. Grégoire2,
1 Saint Mary's
University, Halifax, NS,
2 Geological survey of Canada, NRCan, Ottawa, ON.
Preliminary results obtained early during the summer indicated that laser ablation ICP-MS can be a viable technique for the analysis of metals in APM. In particular, the development of appropriate standards for the purpose of accurate quantification of metals in APM by laser ablation ICP-MS is in progress. APM samples from the July/August 2000 were digested and analysed for Cu, Ni, Pb, Zn, and Cd using solution nebulisation ICP-MS. In general, there is more Pb, Ni, and Cd in APM from sampler No. 2 (downwind from smelter) than in APM from sampler No. 1 (upwind from smelter), which suggests that emission sources other than background sources affected the composition of APM at the location of sampler No. 2. Lead isotope ratios (206Pb:207Pb and 208Pb:206Pb) were also determined using solution nebulisation ICP-MS. Precision for Pb isotope ratio analyses were generally better than 0.8% RSD. Even though some problems were encountered with regard to the plume passing over sampler No. 1 for brief moments (usually less than one hour), the ICP-MS results show that the lead isotope signature is significantly different between the two samplers. The 206Pb:207Pb ratios for sampler No. 1 ("background") are larger than the ones for sampler No. 2 by 4-7%. On the other hand, the 208Pb:206Pb ratios for sampler No. 1 are smaller than the ones for sampler No. 2 by again 4-7%. In general, the range for the 206Pb:207Pb ratio is 1.162-1.202 and 1.104-1.147 for the 5-stage High Volume Cascade Impactor No.1 and No. 2, respectively. The range for the 208Pb:206Pb ratio is 2.04-2.11 and 2.12-2.17 for the sampler No.1 and No. 2, respectively. Another interesting trend is that the 206Pb:207Pb ratio is increasing with decreasing particle size whereas the 208Pb:206Pb ratio decreases with particle sizes. For example, the 206Pb:207Pb ratio for sampler No. 2 is 1.111 and 1.147 for an aerodynamic diameter cutoff of 7.2 m and 0.49 m, respectively. XAFS measurements for copper, nickel, and lead (partially) were done on samples collected in February 2000 and July/August 2000. From the XAFS measurements, chemical speciation of airborne Cu and Ni was determined as a function of particle size (Pb will be completed in 2002). The speciation of airborne copper collected on stages with larger aerodynamic diameter cutoff (e.g., stage 1 and 2) is different than that found at the smaller diameter cutoff (e.g., stage 4 and 5). The XAFS analysis shows clearly that copper sulfate is the dominant copper species on stage 4 and 5. The nickel concentration for stages 1-4 of both samplers was below the detection limit for XAFS measurements and thus XAFS measurements were done only for samples from stage No. 5 of both samplers. The XAFS analysis shows that nickel oxide is the major nickel species in samples from stage No. 5 (cutoff at 0.49 m) of both samplers.
The impact of our findings on ERA of metals can be summarized in the following way. The ICP-MS results (total concentration and Pb ratios vs particle size) show that the metal-containing APM obtained downwind from a Cu smelter have distinct chemical characteristics compared to those obtained upwind. This is also consistent with the speciation results obtained using XAFS that demonstrate, for example, that the Cu species on APM obtained downwind from the smelter are different from those obtained upwind.
Metal deposition histories in lake sediments: Influence of geochemical mobility of metals, diagenesis and local watershed perturbations.
Carignan, R.1, A. Tessier2, L. Rancourt2 and M. Courcelles1.
1Université de Montréal,
Montréal, Qc;
2INRS-Eau, Québec, Qc.
Sediment records are often used to estimate long-term changes in anthropogenic metal emissions. Although dated lake sediment profiles may contain valid historic records of atmospheric trace metal deposition, these records can be substantially altered by watershed perturbations, diagenetic processes and metal mobility near the sediment/water interface. Our project addresses these questions by characterising the chemical behaviour and post-depositional mobility of trace elements (Hg, Cd, Cu, Zn, Ni, Pb, As) in recent lake sediments of boreal Shield lakes exposed to high (Rouyn-Noranda), medium (Haute-Mauricie) and low (Havre St-Pierre) levels of atmospheric pollution. Sediment cores and porewater profiles for trace metals, DOC, sulfides and major ions were obtained from three undisturbed lakes in each region.
Total metal profiles in the three regions show that long-range atmospheric mobility differs widely among trace metals, with Hg > Pb > Zn ~ Cd > Cu ~ Ni; virtually no anthropogenic Cu and Ni were detected at the most remote site (700 km north-east of Montreal). 210Pb dates are generally consistent with other isotopic markers (137Cs and 241Am) and do not reveal any obvious problem with the 210Pb technique. Local perturbations such as wildfires and beaver activity in the watershed have marked effects on Hg profiles. In two lakes, charcoal maxima were followed by 20-30 years of low Hg deposition, suggesting fire-induced Hg volatilisation in watersheds. Post-depositional mobility of trace metals, as determined from concentrations gradients and chemical speciation near the sediment/water interface, can alter the recent (40 y) deposition history of some metals (Hg and Zn), as inferred from sediment profiles.
The project will contribute information required for ERA on "emission pathways and rates of movement of contaminants in the environment". Clarifying the relative contributions of trace elements from natural and anthropogenic sources will provide essential information for making rational environmental decisions.
Metal species associated with atmospheric particulate matter/aerosols – method development
PI: Julia Lu1 (julialu@ryerson.ca)
Research team: Xinbin Feng1, D. Conrad Gregoire2,
Cathy Benic3, W. H. Schroeder3, Grant Edwards4
1 Department of
Chemistry, Biology and Chemical Engineering, Ryerson University, 350
Victoria Street, Toronto, Ontario M5B 2K3
2 Analytical Chemistry Research Laboratories, Geological
Survey of Canada, 601 Booth St., Ottawa, Ontario K1A 0E8
3 Meteorological Service of Canada, Environment Canada, Air
Quality Processes Research Division, 4905 Dufferin St, Toronto,
Ontario M3H 5T4
4 School of Engineering, University of Guelph, Guelph, ON,
N1G 2W1
A methodology has been developed for identification and quantification of metal species associated with atmospheric particulate matter/aerosols. This methodology combines temperature-controlled thermal desorption for separation of metal species with ICP-MS for detection and quantification. Coal-fly ash (provided by Ontario Power Generation) spiked with Hg0, HgCl2, HgO and HgS has been used for testing the new methodology. One batch of samples of airborne particulate matter has been collected and analyzed for mercury species. Preliminary results show that mercury species associated with atmospheric particulate matter/aerosols can be separated and analyzed.
Application of Sensitive Techniques for the Chemical Analysis of Aerosolic Particulates
Spiers, G.A. and A. Cheburkin
Centre for Environmental Monitoring, Laurentian University, Sudbury, ON.
The goal of the methodological development program using the home-built EMMA XRF system is to provide detailed non-destructive chemical analyses, with detection limits in the 1–5 ug gm-1 range. The advanced prototype EMMA instrument, using a monochromatic X-ray source based on a Mo fine focus X-ray tube installed in a vintage Phillips PW1410 generator, a Baltic Scientific detector and a specially designed of pulse-processor card, was constructed on site and tested with a range of soil and geological reference materials prior to application to the analysis of whole filters and particle separates. The system was developed to enable chemical analyses for heavier elements of both materials on either intact, or sub-samples of air-filters, and for single particles of size 20 m or greater.
The data being described in this presentation has been obtained from the preliminary testing of these systems on both powders, single mineral grains, relict magnetic smelter particles extracted from soil LFH horizons, and modern aerosol ejecta from snow collections. The spectra illustrated below demonstrate both the power and the simplicity of the EMMA system. The first spectrum illustrates the qualitative chemical composition of a metal sulphide particle about 35 microns in diameter collected by filtering snow-water through a 0.2-micron filter. The second spectrum illustrates the chemical composition of a spherical smelter particle. Examination of a series of such particles suggests that elements such as As, Se, Pb, Tl and, perhaps, Zn are to be found primarily in the outer ‘layers' of the particles. This suggestion will be further examined with elemental mapping using polished whole particle mounts using an SEM-EDS instrument equipped with digital beam control, and an electron microbeam system.
Results from the preliminary characterization of the magnetic grains and aerosol particles described above has also been completed by scanning electron microscopy, with theses data being described in this presentation. One limitation of the air path configuration of the EMMA system is the inability to quantify elements such as Al, Si, and Na because of absorption of the characteristic radiation in air. A future, more costly, development of the system could include a low-pressure chamber to enable an extension of the analytical capabilities. As illustrated below, the current system does quantify most elements of environmental interest.
The role of bacteria in the mobilization of arsenic from mine impacted sediments.
Palace V1, F Rosensweig2, D Nicholas2, C Baron1, RE Evans1, K Wautier1.
1 Department of Fisheries
and Oceans, Winnipeg, MB
2 University of Montana Microbiology Department, Missoula,
MT
As part of a larger ongoing study to examine the geochemical factors regulating arsenic mobility in historically loaded sediments, bacterial processes that mobilize arsenic are also being examined. The study site (Balmer Lake) is a freshwater system in Northwestern Ontario receiving final tailings from two gold mines. The MITE-RN portion of the project is specifically designed to determine the potential for bacteria that reduce arsenate (AsV) as part of their energy metabolism to contribute to arsenite (AsIII) release from the sediment into the water column. Since iron is the most important factor determining arsenic binding in the sediments, bacterial reduction of iron also constitutes a major portion of the studies. Two 30 cm sediment cores from Balmer Lake were split into 15 cm sections, homogenized and the slurry was used to inoculate media (pH=7.0). Enrichments were incubated at 25ºC in the dark under an atmosphere of N2:CO2:H2 (75:15:10) and were later analyzed for accumulation of As(III). The culture chosen for continued investigation rapidly accumulated As(III) and was designated strain VC-1. An overview of the experiments to further characterize VC-1 will be discussed. While Environmental Risk Assessments (ERAs) are likely to account for the geochemical component of arsenic mobility from mine impacted sediments, the current studies are designed to provide additional information regarding the biotic component of arsenic release to the watercolumn, adding precision for risk assessments based on sediment loadings.