Studies on Chemical Species Dissolved in Shallow Groundwaters of Arima Rhyolite Strata

Abstract

Chemical species of the shallow groundwaters collected from the Arima rhyolite strata around Sanda and Nishiwaki cities are studied. Since the chemical composition of the igneous effusive rock is reasonably representative of rocks of the continental crust, the water quality is important from the geochemical and environmental viewpoints. The concentrations of 28 chemical species, pH and ER are determined by conventional chemical and neutron activation analyses. By showing log-normal distribution character of the concentrations, the median value schematically obtained in the frequency distribution curve is proposed as most suitable as the chemical composition of groundwaters in the strata. It is also pointed out that the CO₂ weathering process is the most dominant phenomenon controlling the water qualities.