ACID RAIN, ACTUAL STATE IN THE JAPAN SEA COAST AND ITS INFLUENCES ON SOIL-PLANT ECOSYSTEM OF SAND DUNE AREA

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Investigation of rainfall in Tottori Prefecture : Mean annual pH of rainfall taken from 17 sites in Tottori prefecture, lies on the Japan sea coast, during 1991-1993. distributed between 4.6 and 4.9, and were lower in the winter and higher in the summer. At the sea coast areas pH of the rainfall less than 4.5 were observed more frequently than the inner areas. Total ions, total non sea salt(nss) ions and nss-SO_4 ^<2-> in the rains also tended to be high in the winter. The amount of wet deposition of nss-SO_4 ^<2-> was about 3g ・ m^<-2> ・ y^<-1> as SO_2 , while the deposition of NO33^- was 1.4g ・ m^<-2> ・ y^<-1> as NO_2 .Influence of acid rain on the soil : Air-dry topsoils of Sand-dune Regosol, Andosol, Brown Forest soil and Red-Yellow soil were filled up in glass columuns, artificial acid rains of various pHs were dropped by an amount corresponded to 3 annual precipitation and the leachates were analyzed. The pH of leachates from each soil column dropped with the artificial acid rain … More of pH4.0 were higher than the original solution pH, showing that the rains were neutralized not only with the exchangeable bases but also with Al and bases dissolved from the amorphous materials and primary minerals The rates of the above reactions to neutralize the acid rain were varied among the soils and the Ph of the rain added. Sanddune Regosol showed an unexpectedly high neutralizing capadity. The effect of acid rain to subsoils were recognized to be less than to the topsoils. The O horizon showed to have ability to neutralize acid rain.Influence of acid rain on the plant growth : By spraying an artificial acid rain on tomatoes grown on Tottori sand dune soil, it was found that the spray on exclusively the tops showed more severe injurious effects than spraying on the tops including the soil on which the crop was grown, indicating that the injuries caused by acid rain was the direct atack on the leaves and stems, and that the soil mitigated the effect of acid rain. Degree of the tolerance of the crops against the direct exposure to acid rain corresponded with that to the acid soil, that is, spinatch was week, peas was a little more tolerant, and corn and soy bean were tolerant. Seedlings were more sensitive to acid rain than the matured crops. Less