Fields Surveys in the Forests Affected by Acid Snow and Rain

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From the measurement of the pH levels and the analysis of components of the fallen snow in Niigata Prefecture, the characteristics of the snow were almost the same as those observed in the snow along the coast of the Sea of Japan from Shimane to Akita Prefecture. Using the multiple regression analysis method, the cause for the lower value of pH in the fresh snow has become evident as a result of mainly the sulfate ions contained in the snow.From some field surveys in the forests at Niigata Prefecture, few withered trees due to acid snow and rain have been found, although the possibility such damaged trees should exist. Cedar, a kind of evergreen tree, has the capability to include more amounts of acidic deposits than the broadleaf trees because of the cedar's rougher trunk and evergreen leaves. While, the flow-down water of melted snow along the trunks of broadleaf trees was neutralized or relaxd with the basic substances released from the trees.The influence of acid rain and snow on soil is not such a serious problem at the present time. However, from the results of the pH measurement of soil and the amounts of leached-elements from the soil, 35% of 113 soil samples mostly gathered in the Niigata Prefecture was estimated to be already acidified.There is a remarkable tendency for the hydrogen ion concentration in snowmelt water in the early spring to be higher than that in the late spring. The fresh fallen snow on the ground is compressed by repeated dissolution and crystallization and forms icy granular snow. The repetition causes sulfate, nitrate and chloride ions to be concentrated near the surface of the icy granular snow. Some laboratory experiments were performed to examine this concentration phenomenon by the formation of spherical ice.