Vesiculation and Calcium Hydrosulfate Crystals in Volcanic Ashes From Sakurajima Volcano and their Environmental effects

樱岛火山的火山灰可分为三大类：黑色火山灰，即最常见的火山灰；红色火山灰，其特征是氧化铁含量高，并存在方石英、石膏和硬沸石；白色火山灰，其特征是丰富的泡状火山玻璃颗粒。由于火山灰在喷发时经历了绝热膨胀和火山气体的化学反应，所以在普通火山灰中以气泡状态存在的火山玻璃颗粒和碳酸氢钙晶体的存在具有重要意义。火山灰及其伴生的火山气体对自然和社会环境的影响主要受两大因素的影响；讨论了火山灰及其伴生气体产生的物理和化学因素对农产品、人体健康和泥石流的影响机理，造成农产品死亡的原因是火山灰-微粒填充在表皮气孔中，导致呼吸停止或功能减退的物理因素和火山气体与水接触时表现为酸的化学因素的综合作用。同时，当人类每天继续吸入相当数量的火山灰时，在不久的将来，出现矽肺或尘肺病等呼吸系统疾病和/或类似疾病的人肯定会出现。火山灰本身的性质与泥石流的成因密切相关。樱岛火山有18条干涸的河流。即使是小雨，由于火山灰本身的物理化学特性，干燥的河流往往会导致大规模的泥石流顺流而下。

Volcanic ashes from Sakurajima Volcano can be grouped into three major classes : black ashes, i. e., most common volcanic ashes ; red ashes characterized by the high-content of ferric iron oxide and the presence of cristobalite, gypsum and anhybrite ; and white ashes characterized by abundant grains of vesiculated volcanic glass. The presence of grains of volcanic glass in the vesiculation state and that of crystals of calcium hydrosulfate in common volcanic ashes are significant in that volcanic ashes were subjected to the adiabatic expansion, and to some chemical reaction due to volcanic gases at the time of eruption.The natural and social environments are affected by two major factors due to volcanic ashes and their accompanying volcanic gases ; physical factors attributed to the substantial nature and grain size of volcanic ash-composing materials, and chemical factors to volcanic gases.Discussions were given to mechanisms that farm products, human health and debris flows are effected by the physical and chemical factors due to volcanic ashes and their accompanying volcanic gases.Farm products are resulted into killing down by a composite factor of the physical factor that volcanic ash-micrograins fill epidermal stomata and, as a result, respiration is stopped or hypofunction takes place, and the chemical factor that volcanic gases behave as acids when they are encountered with water. Meantime, when man continues to inspire a considerable amount of volcanic ash every day, man showing respiratory diseases such as silicosis or pneumoconiosis and/or their similar diseases, will surely come out in not so far future. A close relationship is demonstrated between characteristics of volcanic ash itself and the cause of debris flows. There are eighteen dry rivers at Sakurajima Volcano. Even if it is light rain, dry rivers very often cause a big scale of debris flow down-stream due to physicochemical features of volcanic ash itself.