Characterization of mineralogical controls on ammonium concentrations in deep groundwaters of the Horonobe area, Hokkaido

An investigation of mineralogy and thermodynamic modeling of groundwaters suggests that K-bearing clay minerals (smectite, illite or interstratified illite/smectite), appear to control the NH4+ concentration in groundwaters by ion exchange. Additionally, the selected groundwaters in the Horonobe area seem resemble Japanese gas and oil field groundwaters in terms of NH4+ distribution.