コウスイ ニ フクマレル ムキセイブン ノ カガクテキ トクチョウ (ダイ2ホウ)

Abstract Since acid-rain is a very serious problem in environmental chemistry, the sample collections over a wide area and characterization of the constituents in the rainfall and snowfall are often necessary. The precipitation samples in Yonezawa city from May 1990 to February 1991 were analyzed concerning pH value, electric conductivity (EC) and concentrations of several major ions. The pH values of snowfall distributed in the lower range, when compared with that of rainfall. The annual mean pH values of rainfall and snowfall were 4.8 and 4.7, respectively. The hydrogen-ion concentrations were nearly proportional to the EC values for these rainfall samples. In general, the pH values were low in light rain (under 10mm rainfall), but sometimes they were higher because of clarification by the strong velocity wind, e.g. typhoon. The concentration ratio of Na+/Cl- in precipitation was nearly equal to that of sea water. The EC value of snowfall increased with the increase in average wind velocity. It can therefore be presumed that the sea salt is transported by strong winter monsoon from the Sea of Japan. The data of rainfall samples collected in Yonezawa except NH4+ and NO3- were nearly equal to the background data from Phase-I Study of Acid Precipitation Survey over Japan by Japan Environmental Agency