Geochemical evaluation of regulating factors of magnesium and calcium concentration in Japanese rivers.

Abstract

Japan has been positioned as a model region for weathering research. However, despite this historical background, studies applying non-traditional stable isotopes, which have advanced since the 2000s, for quantifying weathering fluxes have not been actively pursued. In this study, as a preliminary step toward analyses using silicon and magnesium stable isotopes as tracers, we investigated the controlling factors of magnesium concentration in river water. Using data from multiple rounds of comprehensive river sampling conducted between 2022 and 2024, we conducted (1) a comparison with major ion concentration in river water data from the 1950s, (2) an estimation of area-normalized magnesium fluxes by watershed, and (3) a statistical analysis of geological composition in upstream catchments using GIS.