Acid Rain (pH 2.86) in Maebashi

Abstract

Strongly acidic rain (pH 2.86) was observed in Maebashi in June 26, 1981. The rainwater contained H⁺ (1380μequi./l), NH₄⁺ (21.2 ppm), Ca²⁺ (2.9 ppm), Na⁺ (0.74 ppm), K⁺ (0.74 ppm), Mg²⁺ (0.31 ppm), SO₄^2- (46.8 ppm), NO₃^- (95.3 ppm) and Cl^- (13.5 ppm). The total cation concentration was 2778μequi./l and approximatelyequal to that of total anion (2893μequi./l). Sixty samples of acid rain were divided into two groupsin terms of concentration (μequi./l), namely NO₃^->SO₄^2- and SO₄^2->NO₃^-. The hydrogen ion and othercomposition concentration of the rainwaters in the group of NO₃^-> SO₄^2- were clearly higher than those inthe group of SO42-> NO3-. In the group of NO₃^->SO₄^2-, hydrogen ion concentrations were proportionalto NO₃^- and NO₃^-/SO₄^2-, especially under pH 3.50. For reasons as above mentioned, it was presumed thatthe rain was acidified particularly with HNO₃.