Pollutant inputs from the atmosphere and accumulations in soils and vegetation near a nickel–copper smelter at Sudbury, Ontario, Canada

Abstract

The inputs of the airborne pollutants nickel, copper, iron, and sulfur were determined in bulk dustfall–rainfall collection and in snow samples taken along transects originating at a large nickel–copper smelter near Sudbury, Ontario. Determinations were made from 1975 to 1978, which was subsequent to the building of a 380-m smokestack at the smelter in 1972. Atmospheric SO2 was also monitored, using sulfation plates. Higher levels of all smelter pollutants occurred at sites closer to the smelter, compared with sites as far as 60 km SSE. All bulk rainwater samples collected along a 60-km transect SSE of the smelter were found to be acidic, most with a pH of less than 4.0. Since there was no clear gradient of acidity with distance from the smelter, it appears that the acidic precipitation problem is a severe regional one. Simple deposition budgets based on data collected on six 30-day sampling intervals in 1976 and 1977 indicate that less than 3% of the sulfur emitted from the smelter was deposited within a 60-km radius. In contrast, about 42% of the nickel, 40% of the copper, and 52% of the iron emitted from the smelter were calculated to be deposited within a 60-km radius.The contamination of forest soils, soil litter, and vegetation by copper, nickel, iron, and sulfur at sites closer to the smelter has been caused by past as well as ongoing emissions. In soil profiles, the metals were concentrated in the surface organic horizons, relative to deeper mineral soils. Surface soils up to 70 km from the smelter showed elevated nickel and copper concentrations. Elevated concentrations of these same metals in the foliage of a number of tree species were detectable at least to 12 km from the smelter. The horsetail Equisetum sylvaticum showed especially high concentrations of sulfur, while the moss Polytrichum commune was an accumulator of nickel, copper, and sulfur at sites up to 6 km. No consistent trends with distance occurred for foliar levels of the bases calcium, magnesium, and potassium. However, higher calcium concentrations occurred in forest litter collected at control sites, compared with sites closer to the smelter.