Biogenic sulfur and the acidity of rainfall in remote areas of Canada.

Sulfur released from any given natural or anthropogenic source carries an isotopic signature that can be used to trace its flow through the environment. Measurements of the concentration and isotopic composition of sulfur in weekly bulk precipitation samples collected over a 4-year period at a remote location in northern Ontario were recorded. The long-term isotopic data and the measurement on the production and release of dimethyl sulfide from boreal wetlands show that biogenic sources can account for up to 30 percent of the acidifying sulfur burden in the atmosphere in remote areas of Canada. The data suggest that significant biological reemission of anthropogenic sulfur is occurring. The role of this process in the continuing acidification of the environment for years to come must be a matter of concern.