Impact of a base metal smelter on the geochemistry of soils of the Flin Flon region, Manitoba and Saskatchewan

The regional dispersal patterns of six trace metals (As, Cd, Cu, Hg, Ph, Zn ) emitted from the base metal smelter at Flin Flon were examined in surface soils and at depth, using an extensive regional geochemical database for h umus and the underlying till. Humus is enriched in those elements emitted f rom the smelter, and regional dispersal patterns reflect the historical rec ord of smelter contamination. The concentrations of the smelter metals decr ease with increasing distance from the stack, until background values are r eached, indicating atmospheric fallout from the smelter plume. Smelter cont amination is generally restricted to the surface organic-rich horizons, and concentrations of smelter metals in till reflect the absence of significan t contamination at depth in the upper C horizon of soils. The maximum radiu s of contamination varies among the major smelter metals, ranging from 70 k m for Cd to 104 km for As. No direct relationship exists among emission, de position, and sink concentrations, reflecting the complexity of factors inf luencing total metal concentrations in soils. Factors considered in this st udy include the natural geochemical signature of the underlying substrate, natural soil-forming processes such as biogeochemical enrichment in the sur face organic layer and post-depositional mobilization of metals, and the va riation in total metal concentrations among the different fractions and typ es of samples analysed. With increasing distance from the smelter, these fa ctors become significant, and the relative proportion of anthropogenic cont amination in the surface terrestrial environment is more difficult to estim ate.