The Contamination and Recovery of Natural Ecosystems by Smelting and Mining Activities at Sudbury, Ontario

Abstract

The mining and smelting of nickel, copper, cobalt iron, and other precious metals at Sudbury, Ontario resulted over many years, in the largest point source of sulphur dioxide in the world. The smelters have run since the early years of the 20th century and continue to be major producers of nickel and copper. Emissions as high as 3.2 million tons of SO2 per year were occurring by the late 1960's. The area around the smelters is one of thin, podsolic soils originally covered with forest. A very large number of lakes also occur in the area amongst the bedrock of the Pre-Cambrian Shield. The damage to the forests, the soil microbial flora and fauna, and to the soils was massive, affecting an inner zone of several thousand square kilometres. The major phytotoxic factor was sulphur dioxide and sulphuric acid aerosol, but large, toxic accumulations of heavy metals occurred in the soils and the leachates acidified and added metals to the aquatic systems. Many lakes became devoid of fish and of zooplankton. Acid and metal-tolerant varieties of algae, of soil fungi, of grasses and trees were evolved. Since 1972, a 381 m. high Superstack has been in operation. At the same time, a small but very polluting smelter at Coniston was closed. Regional air quality has greatly improved. The paper focuses on the extent and pattern of response of the terrestrial and aquatic systems to the aerial contamination, and then on the substantial recovery in ecosystem function and biodiversity since clean up began.