The total annual emissions of sulfur oxides and nitrogen oxides in Canada are estimated to be 7.2 ร 106 t and 1.4 x 106 t, respectively. These figures represent 5% and 2%, respectively, of the estimated worldwide authropogenic emissions. Nearly two-thirds of the Canadian SO 2 emissions come from primary smelters located in low population areas. The remainder originate from natural gas processing, pulp mills, fuel combustion and transportation in the more heavily populated areas. Transportation is the major source of oxides of nitrogen.
No co-ordinated precipitation sampling has been carried out on a national basis prior to the establishment of the World Meteorological Organization regional stations in 1974, but several local projects in problem areas have been conducted over the last 20 yr. These data are reviewed with respect to sulphate and nitrate content, and when available, the pH.
The geographical distribution of acid rain in Canada is discussed in relation to main source areas of pollutants, prevailing meteorological conditions and precipitation type.
Finally, the extent of current and potential problems associated with acid rain is discussed, and current and recommended future monitoring and research programs are outlined.