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Project leader: Dr. Peter Outridge

The project will provide source apportionment data to national and international clients (including AMAP, Health Canada, Northern Contaminants Program) for the purposes of human and environmental risk assessment, and will use the clients' own communication channels to disseminate findings to public and scientific audiences. It will investigate long-term temporal variations of metals, thereby increasing our understanding of the role of natural and anthropogenic variations and processes in controlling human metal exposure. The objectives are to:

• evaluate the protocols that use natural archives for apportionment of metals in atmospheric deposition;
• investigate the archives' chemical and physical characteristics that determine archive reliability;
• conduct apportionment calculations of priority metals (Hg, Cd, Pb) in deposition and country foods in the Arctic to aid client's on-going risk assessments;
• develop procedures that will improve identification of different metal sources.

The validation objective concerning metals in natural archives will be accomplished by:

1. resampling 6 lake sediments in the Arctic and near Flin Flon, Manitoba, which were originally cored and analysed 10-20 yr ago, and establishing whether metal profiles (especially of Hg, Cd, Pb) are stable over time
2. cross-comparing historical trends determined directly in deposition or in the atmosphere with the corresponding profiles in nearby archives
   1. lake sediments
   2. peat bogs
   3. trees
   4. glacial ice

The null hypothesis is that archives do not reliably represent historical trends of atmospheric metals. To suggest which parameters may be important determinants of archive reliability, archives will be characterized chemically, physically, mineralogically and biologically as appropriate.

The Arctic source apportionment objective will be accomplished for atmospheric deposition by using the temporal trends in those archives which have been validated; for country foods (beluga, seals, caribou), the teeth of animals from modern and pre-industrial (i.e. pre-1800) time periods will be used. Pre-industrial and modern metal levels will be compared, and any increase that is not attributable to natural geological or biological processes will be tentatively ascribed to an anthropogenic source. For Pb, sources will be identified by isotopic analyses. The null hyypothesis is that anthropogenic sources have not affected modern levels of metals in Arctic atmosphere or in country foods. Novel procedures for source identification and discrimination will be investigated, including methods for determining Hg isotopic source signatures using multicollector ICP-MS, and laboratory simulation experiments and conceptual interpretations of physico-chemical parameters to increase understanding of the processes driving metal speciation and mobility in sediment.