The nature and fate of particulate emissions from an isolated power plant in the Athabasca oil sands area of western Canada are investigated on the basis of measurements of particulate elemental concentrations in the air 80 km from the source late one winter and close to the source early the next summer, of dry deposition patterns of particulate sulfur and heavy metals in the early summer, and of total (wet and dry) deposition patterns of major ions and metals during two winters. Results of plume chemistry studies to investigate SO2 oxidation during summer and winter and of fly-ash analyses for heavy metals are also used. It is found that: (1) many elements in particulate matter deposited around the plant originate primarily from a different source in summer and in winter; (2) deposition near the source is more alkaline than in outlying areas; (3) wet and dry deposition of acidic oxides of sulfur and nitrogen from the power-plant emissions appear to be the main source of snowpack acidification in downwind areas; and (4) acidic compounds can be transported over long distances before being removed.