著者

志田 惇一 持木 一夫

出版者

山形大学

雑誌

山形大学紀要. 工学 (ISSN:0085834X)

巻号頁・発行日

vol.23, no.1, pp.25-31, 1994-01-31

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The characterization of the precipitation in Yamagata prefecture was investigated and discussed. The samples collected every rainfall and snowfall in Yonezawa city from May 1990 to February 1992 were analyzed concerning pH value, electric conductivity (EC) and concentration of major ions (Na+, K+, NH4+, Ca2+, Mg2+, Cl-, NO3- and SO42-). These data were compared with the date observed in Yamagata and Sakata cities. The annual mean pH values of rainfall and snowfall ranged frorn 4.6 to 4.9 and from 4.5 to 5.1, respectively. The lowest pH value Was 3.7 in each city. The total concentration of major ions was very dependent on the amounts of sea salts dissolved in precipitation, and the concentration in Sakata was higher about 4 or 5 times than the one in Yamagata or Yonezawa. It was forecast that a regional difference of pH value between rainfall and snowfall was owing to a washout phenomenon. The equivalent concentration ratio of NO3- to nss-SO42- has been increasing over a long period of time in every city, and it is presumed that nss-Cl- from HCl contribute to acidifying the precipitation, because the monthly mean pH values gradually decreased with an increase in the equivalent concentration of [(NO3- + nss-SO42- + nss-Cl-)] - [(NH4+ + nss-Ca2+)].