いわき地域における降水の酸性化に及ぼす各種イオンの影響

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The acidification of rainfall has globally become one of the serious environmental problems. whichhas gradually caused by the industrial development. the improvement of life style and so on. Even inIwaki, without exception, the acid rain which was determined to be pH<5.6 was observed. its meanpH value was measured to be 4.1 in 1991.In this study. the influence on the constituents of the rainfall to its acidification was investigatedexperimentally. At the fixed point in lwaki. every rainfall was collected using with an auto-samplingapparatus with a rain sensor, which sampled initial 5mm of precipitation every lmm and collected theresidual together as sequential precipitation. The investigation period was from June of 1992 to Feb- ruary of 1993. which was divided into three seasons ; summer (June-August), autumn (September-No- vember). winter (December February).Every constituent concentration of initial 1mm of precipitation was remarkably distinguished fromthat of the sequential by comparison of their concentrations. the mean pH value of the rainfall atthis fixed point was 3.8. and 3.9 in summer. autumn and winter of I992-1993. respectively. and theacidification of the rainfall has become stronger than in 1991.when a low atmospheric pressure was passing along the south shore of Japan with growing up inautumn. the components of the rainfall at this fixed point was storongly affected by the sea-salt par- ticles. In this season. for example both Na^+ and Cl^- concentration were remarkably higher and themean contribution ratio of the sea salt particles of SO_4^2- concentration was 25 percent. which was astwice as that in the other seasons. NH_4^+ and nssCa^2+ (eliminated from the seasalt particles) weretended to become higher in summer and in- winter. respectively. NH_4^+ was suggested to be the moreimportant ion than nssCa^2+in the prevention from the acidification of the rainfall, because the meannssCa^2+/NH_4+ equivalent ratio of the rainfall was 0.66. On the other hand. both nssSO_4^2- and NO_3^-concentration of the rainfall were shown to be higher in winter than in the other seasons. Since themean NO_3^-/nssSO_4^2- equivalent ratio was 0.97. NO_3^- was found to be as important as nssSO_4^2-inthe acidification of the rainfall.
福島工業高等専門学校の論文

いわき地域における降水の酸性化に及ぼす各種イオンの影響

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