The Global Distribution of Acidifying Wet Deposition

The acid-base status of precipitation is a result of a balance between acidifying compounds--mainly oxides of sulfur and nitrogen--and alkaline compounds--mainly ammonia and alkaline material in windblown soil dust. We use current models of the global atmospheric distribution of such compounds to estimate the geographical distribution of pH in precipitation and of the rate of deposition of hydrogen ion or bicarbonate ion. The lowest pH values--mainly due to high concentration of sulfuric acid--occur in eastern parts of North America, Europe, and China. A comparison with observed pH values shows fair agreement in most parts of the world. However, in some areas, e.g. western North America, southwestern Europe, and northern China the estimated pH is too low, indicating that we have…