Changes in metals and metalloids concentrations in spring waters after the 2016 Kumamoto earthquake

To understand the influence of earthquakes on hydrochemical compositions of groundwater particularly for trace metals，water samples were collected from 16 representative spring sites after the occur rence of the 2016 Kumamoto earthquake near the epicenter and fault zone. Among multiple elements measured in this study，Al，Fe，Mn and V increased their concentrations just after the earthquake and subsequently declined for some springs. Our observations suggest that seismic shaking enhanced release of Al，Fe and Mn as colloidal matters that led concentrations of these elements increased in groundwater. Similar increase in concentrations was confirmed for V that might be triggered by disso lution of rock materials. These observations seem to be explained by both mitigation of colloidal release and dilution by groundwater with relatively low concentrations. Our survey showed that the disturbed hydrochemical signatures is suggested to be returned to steady state in annual hydrological cycle.