CHARACTERISTIC OF WATER CHEMISTRY FOR ARIMA TYPE DEEP THERMAL WATER IN THE KINOKAWA RIVER CATCHMENT, KII PENINSULA, JAPAN

Abstract

All soluble substances for coastal shallow well waters were higher than those for the inland well waters in the Kinokawa River catchment along the Median Tectonic Line in Wakayama Prefecture, Japan. Coastal areas were thought to have been contaminated by sewage wastewater due to a high population. Shallow groundwater is thought to have derived from precipitation because all shallow groundwater is on the Global Meteoric Water Line. There are many hot springs in the Kinokawa River catchment along the Median Tectonic Line in Wakayama. Most hot spring waters are thought to originate from mixing of shallow groundwater and Arima type deep thermal water because of their δ¹⁸O and δD values. High Li⁺ concentration water was found for Arima type deep thermal water. In particular, Li⁺ concentration of Nohan No.5 borehole, 1100m in depth, in the center of Kinokawa River catchment reached 100 mg/l and this value was the highest in Japan. However, both δ¹⁸O and δD values for hot spring waters did not always increase with Li⁺ and HCO₃^- concentrations although both δ¹⁸O and δD values increased with Na⁺ and Cl^- concentrations. Li⁺ concentration for hot springs increased with HCO₃^- concentration. Therefore, the Li source was determined not to be different from Na⁺ and Cl^- source.