新潟県中越地域における地下水中のヒ素濃度の地球化学的研究

抄録

Groundwater qualities were geochemically examined for As-rich wells in Chuetsu area of Niigata Prefecture. The results showed the partial overlap of high As concentration zone and high temperature zone caused by hydrothermal effect. Well waters were classified by water qualities. As-rich groundwaters mainly belonged to Na-HCO₃ type. But neither hydrothermal Na-HCO₃ type groundwater of higher temperature nor hydrothermal Na-Cl type groundwater originating from fossil seawater showed high As concentration. These results suggested that As was dissolved from As compounds in alluvia into hydrothermal Na-HCO₃ type water. This hypothesis was supported by the correlation between As and SO₄²-concentrations of As-rich Na-HCO₃ type waters.