Acid deposition chemistry in Asia, Europe, and North America

Abstract

Acid deposition issue is addressed from the viewpoint of atmospheric chemistry, and precipitation chemistry in Japan was discussed on a global scale. This environmental issue was identified as acidification of atmosphere by increasing concentrations of sulfuric and nitric acids and subsequent acidification of terrestrial environment by deposition of these acids. Precipitation in Japan was characterized as follows: (1) Sulfuric acid (38.6 μ eq L −1) exceeded nitric acid (14.1 μ eq L −1) on an annual mean basis, (2) These acids were neutralized by ammonia and alkaline calcium species to give an annual mean, pH 4.8, and (3) Spatial distributions of concentrations of sulfuric and nitric acids were suggested rather uniform over the country. On a regional scale, Asia showed the highest median concentration, 70 μ eq L −1, of sulfuric acid, and was followed by Europe (35 μ eq L −1), former Soviet Union (31 μ eq L −1), and further by North America (15 μ eq L −1). For nitric acid, however, Europe recorded a maximum level, 35 μ eq L −1, and the second maximum occurred in Asia, North America, and former Soviet Union: 16, 15, 15 μ eq L −1, respectively.