Archives of Environmental Change
Our main goal in the broadest sense is to analyse, understand, and model the impacts of human activities on the geochemical cycles of the elements. Of particular interest are Pb and Sb because they have no biological functions and both are potentially toxic. To develop a quantitative understanding of human impacts, however, it is necessary to first understand the natural geochemical cycles of the elements: here there are many gaps in our knowledge. For example: what were the natural rates of atmospheric deposition of trace metals such as Pb in the pre-industrial past? How much of the Pb flux was due simply to soil dust particles derived from the weathering of crustal rocks, and how much due to other sources? How did the soil dust flux vary with climate change during the Holocene?
We use a retrospective approach to quantify the natural fluxes of trace elements from soils, via the atmosphere, to terrestrial ecosystems - this is done using peat cores from bogs as well as ice cores from the Canadian Arctic. Peat cores from ombrotrophic bogs as well as polar snow and ice receive trace elements exclusively from the atmosphere. By continuously coring downward through peat or ice we are able to derive insight into past rates of atmospheric deposition extending back in time thousands of years. Using appropriate age dating methods, suitable age-depth models and very careful determinations of trace element concentrations, it is possible to reconstruct the changing rates and predominant sources of a wide variety of atmospheric trace elements.