Distribution and potential bioavailability of anthropogenic metals in Sudbury soils

Sudbury, Ontario has developed into one of the largest metal producing areas in the world. Metal mining and smelting has resulted in massive atmospheric emissions of sulphur. In the early 1960s, the smelting complex was one of the largest point sources of sulphur dioxide (SO2) emissions in the world at over 2,000,000 tonnes per year. By the 1990s, the implementation of reduction and abatement measures brought this number down to about 200,000 tonnes per year. In addition, 1500 tonnes of metal particulates were carried to the atmosphere annually in the hot gas plume. The particulates were composed mostly of fine iron-rich fly-ash containing nickel, copper and other trace metals. This massive release of pollutants resulted in a barren landscape with acidified soils contaminated with metals. The Sudbury region has therefore provided an opportunistic macrocosm to study the effects of severe acidification and metal pollution on soils and ecosystems. This study described the nature and distribution of metals and metal-rich fallout particles on regional soils as well as the regional impact of smelter emissions on metal distribution. It also described the morphology, mineralogy and chemistry of metal-rich fragments filtered by the LFH horizons of soil particles within the Sudbury smelter zone. These particles contain magnetite, maghemite, and trevorite with varying quantities of iron, nickel, copper, cobalt, chromium, lead, arsenic, selenium, manganese and zinc. This paper presented preliminary data on the metal bioavailability from the regional soils. The effects of intensive mining and smelting activity over the past century in Sudbury was illustrated by regional distribution patterns for anthropogenic metals. The study has shown that the effects of aerosolic fallout are retained in the LFH horizons of soils and can be seen farther than 100 km away from the smelting epicenter