Large-scale atmospheric sulfur studies in Canada

Abstract

This review describes efforts underway in Canada to investigate large-scale atmospheric sulfur pollution. An assessment of the susceptibility of various parts of the country, in terms of receptor sensitivity, meteorological regime and source-receptor configuration, as well as evidence of ecosystem damage in North America and Europe, has led the federal Department of Fisheries and Environment to undertake a comprehensive program to investigate the long-range transport of air pollutants in eastern Canada. The program includes studies of emissions, atmospheric phenomena and aquatic and terrestrial ecosystem effects. Atmospheric aspects of particular interest include long-range transport, regional particulate-sulfate levels and the acidity and sulfate content of precipitation. Results from an intensive, month-long study of paniculate and precipitation sulfate in eastern Canada indicate that episodes of elevated paniculate sulfate concentration occur over a large part of the region, usually in association with the southerly flows behind large areas of high pressure situated over the eastern portion of the continent. Most severely affected is the lower Great Lakes region, with 24 h average sulfate concentrations in the 40–50μg m −3 range and averages for the period near 10 μg m −3. Precipitation chemistry measurements from this study and other ongoing monitoring programs indicate that the southeastern portion of the country is also affected by high precipitation-sulfate concentrations and low pH values, typically 5 mg l −1 and 4.3 respectively. The geographical distributions of both particulate-sulfate and precipitation acidity are consistent with those found in the eastern United States. Air pollution problems associated with sulfur compounds are of a large-regional nature in eastern North America, affecting both Canada and the United States. International approaches to their further study and eventual solution are a necessity.