ACID RAIN DISSOLVED WITH VOLCANIC GASES AND ITS CHEMICAL REACTION WITH SOIL

对1994~1996年库州火山富马林区附近雨水的化学特征及其酸化的区域扩展进行了研究。雨水收集使用露天类型的雨水收集器，设置在11个不同的地点，距离福马罗克地区7公里，并每隔两周采样一次。延胡索区附近的pH值范围为2.5~4，并随距离的增加而升高。在距富马林区1.5公里范围内，Cl~-和SO_4~(2-)浓度占总阴离子浓度的90%以上，H~(2+)浓度以阳离子为主。根据氯气浓度的面积分布和各集雨期间的降水持续时间计算出的HCl沉降量，估算了从气孔中释放出的HCl气体的排放量。在1995年10月11日喷发活动开始之前，计算出的HCl排放量从1995年7月的2t/d迅速增加到6.3t/d。这一行为表明，在喷发前两个半月，深部岩浆的活动已经增加。采用具有酸吸附能力的赤潮土制作土柱，进行了酸雨入渗及与土壤化学反应的试验。以11.5 mm/h的降水强度向色谱柱投加PH3的人工酸雨，酸雨总量相当于4000 mm。在整个实验过程中，柱外排出水的pH值均大于5.5，说明渗入的酸雨在流经柱的过程中被中和，酸雨中的主要阴离子组分--硫酸根离子主要被土壤吸附，且随着柱顶距离的增加，离子的吸附量迅速下降。

Chemical characteristics of rain water and areal extension of its acidification in the vicinity of fumarolic area at Kuju volcano were studied between 1994 and 1996. Rain water was collected using rain collectors of open air type set at eleven different sites as far as 7km from the fumarolic area, and sampled at intervals of two weeks. The pH values in the vary vicinity of the fumarolic area ranged from 2.5 to 4, and rose with an increase in distance. Within 1.5km from the fumarolic area, concentrations of Cl^- and SO_4^<2-> occupied more than 90% out of the total anion concentration, and H^+ concentration dominated the cation. Discharge rate of HCl gas emitted from the fumaroles were estimated using the total amount of deposited HCl calculated from areal distributions of Cl concentration and the duration of precipitation during each rain collecting periods. Calculated discharge rate of HCl quickly increased from 2 t/d to 6.3 t/d in July 1995 prior to the eruptive activity started on October 11,1995. This behavior implies that activity of magma at depth has increased two and half months before the eruption. Experiments on acid rain infiltration and chemical reaction with soil was carried out using soil column made with Akahoya soil having acid adsorption capacity. Artificial acid rain of pH3 was supplied to the column at a precipitation intensity of 11.5 mm/h for the total amount of being equivalent to 4000mm. Discharged water from the column showed pH values higher than 5.5 throughout the period of experiment, indicating infiltrated acid rain was neutralized while flowing down the column, Sulphate ion being a dominant anion component of acid rain was mostly adsorbed by soil and adsorbed amount of the ion decreased quickly with distance from the top of the column.