In order to identify the origin of saline groundwater in the eastern part of Jeju volcanic island, Korea, a hydrogeochemical and isotopic study has been carried out for 18 observation wells located in east and southeast coastal regions. The total dissolved solid contents of groundwaters are highly variable (77-21,782 mg/l). Oxygen, hydrogen, sulfur, and strontium isotopic data clearly show that the saline water results from mixing of groundwater with seawater. Strontium isotopic compositions and Br/Cl and I/Cl ratios strongly suggest that the source of salinity is modern seawater intrusion. Hydrogeochemical characteristics based on bivariate diagrams of major and minor ions show that changes in the chemical composition of groundwater are mainly controlled by the salinization process followed by cation-exchange reactions. The highly permeable aquifers at the east coastal region are characterized by low hydraulic gradient and discharge rate and high hydraulic conductivity as compared with other regions. These properties enhance the salinization of groundwater observed in the study area. Based on the Cl, Br, and δ 18O data, seawater was determined to have intruded inland some 2.5 km from the coastline. Considering the poor correlation of sampling depth and Cl concentrations observed, the position of seawater-freshwater interface is not uniformly distributed in the study area, due to heterogeneities of the basaltic aquifers.
Bibliographical noteFunding Information:
This work was supported by a grant (3-2-1) from the Sustainable Water Resources Research Center of 21st Century Frontier Research Program and a Jeju Development Institute grant. It was also partly supported by the Korea Science and Engineering Foundation grant (R01-2000-00060). We thank two reviewers James R. Lawrence and A. Zuber as well as an editor P. Van Cappellen for their critical comments. Comments on the manuscript by Phil Hays of the USGS also helped to improve the quality of presentation.
All Science Journal Classification (ASJC) codes
- Water Science and Technology