Partial neutralization of acid rain by Asian eolian dust transported over a long distance

Abstract

Abstract The chemical and mineralogical compositions of 11 wet eolian dust materials collected from “red snow” and “mud rain” or two dry air-fall deposits in Japan were studied. Asian eolian dust materials deposited from 1925 to 1961 were characterized by a considerable amount of calcite, which was low in the eolian dust materials deposited from 1966 to 1987. Calcite in the eolian dust may have been consumed to neutralize acids in rainwater and snow-water. Artificial acid rain solutions with a H2SO4/HNO3 molar ratio of 1.0 and pH values of 3, 4, or 5 were neutralized by the addition of loess, a saline soil, or Asian eolian dust materials containing a considerable amount of calcite at concentrations above 400, 40, and 8 mg- liter-1, respectively. The results obtained should be closely examined in terms of the role and significance of Asian eolian dust transported over a long distance as a neutralizing agent of acid rain or acid snow, which is associated with the accumulation of SOx and NOX emissions from i...