The mechanism of the preferential elution of the major ion and oxygen isotope ratio in acidic snow melting water by acid shock in the snowfield of Japan

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(1) To recognize the reality of acidity snow, the analyses have been carried out ofacidity, electrical conductivity, major chemical features in precipitation gathered at Nagaoka City throughout the whole year from 1987. A regression straight line of the year-to-year pH variations of precipitation shows a decreasing tendency from pH value 4.9 at the end of 1987's to 4.5 at the end of 1999's. The seasonal variation of average pH value for past 13 years shows a tendency becoming high in around April and low in the winter season and June. As for why pH is low for the winter season, the effect ofa pollutant from the continent is considered to be big. The high pH value in around April is thought to be due to the influence of"Kosa". The cause of the low pH value in June is indistinct. These results are compared with that of the snow on Antarctica with little influence of human activities.(2) The relationships were examined between oxygen isotope and major ion concentration in precipitation of winter from November 1994 to March 1995. The average δ<18>^O of all precipitation is -9.3%_o, the δ<18>^O value of hail is lowest and that of rain is highest. Some strong correlations between δ<18>^O and a special ion cannot be found find, but a correlation with calcium ion was found a little.(3) The snow of Nagaoka was examined to grasp the reality of "acid shock" in Honshu covered by wet snow of large quantities. The effluence speed of an ion in the snow shows some differences by ion seed. Clear analyses in details are to be carried out in future.(4) To elucidate the reason why effluence speeds of ions are different among different ions, DSC(differential scanning calorimetry) analyses of various solutions are carried out and an interesting result was provided, but the details are indistinct.