Acid Rivers in Volcanic Regions and Efforts to Improve Their Water Quality

Acid river systems and the actual situation of neutralization at Kusatsu-Shirane volcano, Gunma Prefecture, Ebino highlands Kirishima volcanoes, Miyazaki are reviewed. In case acid system sources water volcanic acidic hot springs mine drainage (AMD) from closed sulfur mines. Volcanic AMD have different effects on environment. Arsenic is predominantly supplied springs, heavy metals such as lead AMD. The volcano targets Kusatsu region's largest source components, resulting in a significant quality improvement downstream river. directly injects neutralizer prepared powdered limestone into products formed finally accumulated dam constructed to function sedimentation basin. Then, dredged sediment dumped dedicated disposal sites. Highlands (Iwoyama volcano), complex, an eruption 2018 caused pollution. Phreatic eruptions Iwoyama triggered discharges hydrothermal fluids containing large amounts arsenic vents newly opened with eruptive events, deterioration damage local agriculture. Because discharge continued even after activity ended, Prefecture decided neutralize Highlands. After starting neutralization, rivers improved significantly. amount treatment required for not very large, passive method was adopted enable low-cost operation.