THE CHEMICAL AND PHYSICAL CHARACTERISTICS OF HEAVY-METALS IN HUMUS AND TILL IN THE VICINITY OF THE BASE-METAL SMELTER AT FLIN-FLON, MANITOBA, CANADA

Trace element geochemistry of humus (< 0.425 mm) and till (< 0.002 mm) collected in the Flin Flon-Snow Lake area, northern Manitoba and Sask atchewan, provides a regional context for assessing smelter contaminat ion in the environment. The area includes a Cu-Zn smelter known to dis charge As, Cd, Cu, Fe, Hg, Pb, and Zn. In this study, sequential extra ction analyses, scanning electron microscopy and x-ray diffraction ana lyses were used on a suite of samples to determine: (1) the chemical a nd physical characteristics of heavy metals in surficial sediments rel ated to distance from the smelter, (2) criteria for assessing the rela tive contribution of these metals from natural and anthropogenic sourc es, and (3) the potential of these metals for remobilization in the en vironment. Humus geochemistry reflects the anthropogenic and natural c omponent of heavy metal concentrations. Smelter-related elements show anomalously high values adjacent to the smelter, decreasing with dista nce until background values are reached at 70-104 km, depending on the element. In humus, Zn is associated primarily with labile phases; Hg with non-labile phases. Adjacent to the smelter, high proportions and concentrations of Zn and Hg in non-labile phases, indicative of smelte r-derived particulates, are confirmed by SEM examination. The particle s occur as spheres, irregular grains, and with organics. With increasi ng distance from the smelter, the geochemical response to bedrock comp osition is more obvious than the anthropogenic input. Till geochemistr y reflects the natural variation imposed by bedrock composition. At hi ghly contaminated sites (< 3 km from the smelter), increased percentag es of smelter-related elements in labile phases suggests heavy metals are leached from humus to the underlying sediment.