Research Priorities > Sources Domain
 

Development of Methods for Quantification and Apportionment of Metal Sources
  Research Team
G. C. Edwards (University of Guelph) - PI; R. Carignan (Université du Québec, INRS-Eau), PI; B. Boudreau (Dalhousie); A. Tessier (Université de Québec, INRS-Eau); M. Lamoureux (St. Mary's University) - PI

 
  Collaborators
C. Grégoire (NRCan, Geological Survey of Canada); P. Rasmussen (NRCan, Geological Survey of Canada); B. Schroeder (AES, Environment Canada)

 
  Summary
The ability to assess whether the presence of metals in the environment originates from anthropogenic or natural sources is crucial for determining the most appropriate regulation of sources. This requires both a more complete quantification and characterization of metal emissions from natural and anthropogenic sources, and analytical techniques or criteria to determine the source at the receptor site through knowledge of the chemical speciation of metal particulates. In the present project, it was proposed to address these knowledge gaps through a program which includes methods development and natural metal emission measurement research, development of analytical techniques for metal speciation, and the study of diagenesis to determine whether remote lake sediment records can be used as evidence of long-range transport of metals from anthropogenic sources.

 
  Scientific Background
Metals in the environment can arise from both natural and anthropogenic sources. The overall issue, is to determine whether the metals that are posing public health and environmental problems originate from natural or anthropogenic sources, and thus identify the most appropriate risk management strategy. To address this issue properly, metal releases to the atmosphere must be reliably quantified both for anthropogenic and natural sources. Additionally, to understand the role and influence of natural versus anthropogenic metal sources from emission to deposition, it is important to know the properties of the emissions that influence their transport and transformation in the atmosphere, such as the distribution of metals as a function of particle size and the metal species on the particles.

There are large uncertainties associated with estimates of natural metal emissions to the environment (Rasmussen, 1998). Without these natural sources inventories, the relative contribution of anthropogenic sources cannot be adequately assessed for regulatory and mitigation purposes. The uncertainties are largely due to technological limitations and incomplete sources quantification, therefore on of the research program=s objectives was to develop metal flux measurement methods and to apply them for measuring a variety of natural sources.

Fine metal particles may be subject to long-range transport. Therefore, it is imperative, from an ecological risk assessment point of view, to determine sources of airborne particles and identify individual particles on the basis of size fraction and their chemical composition, so as to have an improved understanding of the sources and fates of metals in airborne particulates. The objectives of these studies are to develop analytical techniques and to assemble criteria which can be used to determine the source of deposited metals.

Metal emissions from anthropogenic or natural sources may be transported to the aquatic environment, and can be manifested as enhanced metal concentrations in lake sediments close to point sources. Such sediment profiles have been interpreted as evidence for increased anthropogenic metal loading in the recent past (Lindqvist et al. 1991). In the case of certain elements, however, surface enrichment may result from natural processes (Carignan and Tessier 1985). The changes that occur after burial, due to physical, chemicals and biological processes ("diagenesis"), are important controls on sediment profiles. The sensitivity to sediment diagenesis varies from metal to metal; therefore the objective was to exploit these characteristics to determine source emissions.

The objectives of the individual projects are designed to meet the long-term objectives of the projects which are:
(i) to determine what proportion of observed metal loadings in various ecosystems is due to atmospheric deposition from anthropogenic activities versus natural sources, and
(ii) to provide high quality emission data, methods, and criteria that can be used for the ecological risk assessment of metals.

 
  Practical Background
Over the time frame 1998-2004, we propose to develop techniques for particulate metal flux measurements and to apply them to measure natural fluxes from various natural settings (Edwards), to develop new analytical techniques to determine metal species by particulate size (Lamoureux), and to study the effect of diagenesis to determine whether remove lake sediment records can be used as evidence of long-range transport from anthropogenic sources (Carignan). Various funding options are being explored for the period 1999-2004 (e.g., applications to NSERC for University-Industry funding in the <Research Network> or <Cooperative Research and Development> areas). Since it was not expected to begin receiving funding from these sources until 1999 at the earliest, the 1998-99 research program was implemented on a budget of $108,000.

 
  Overall Goals
An overriding goal for the current funding exercise was to maintain and foster interactions among those MITE researchers who are involved in research on the sources of metals in the environment. The 1998-99 time-frame was thus seen as a transition year, during which these contacts were maintained even while we worked on obtaining complementary funding from NSERC and other sources. Each sub-project was designed to test certain key hypotheses and to yield short-term results that will help us to refine the experimental approaches for the subsequent field work.

 
  References
Carignan, R. and A. Tessier, 1985, Science, 228: 1524-1526.

Lindqvist, O., K. Johansson, M. Aastrup, A. Andersson, L. Bringmark, G. Hovsenius, L. Hakanson, A. Iverfeldt, M. Meili, and B. Timm. 1991. Water Air Soil Pollut. 55:1-2.

Rasmussen, P.E. 1998. Environ. Geol. 33: 96-108.