Abstract
Geoenvironmental problems in the Shiroishi Plain such as land subsidence, saltwater intrusion into groundwater and the change of strength characteristics of marine clay deposit, are all related to groundwater movement. To investigate the mechanism of saltwater intrusion into groundwater in the plain, water quality, natural radioactive isotopes and environmental stable isotopes analyses were conducted, directing our attention to the vertical migration of considered cations/anions. The results suggest that the mechanism of saltation of groundwater can be explained as the mixing of groundwater with fossilized seawater in Holocene marine deposit by seasonal pumping-up of groundwater.
