Abstract:

Seawater intrusion is a major environmental geological problem in coastal areas, and the analysis of chemical characteristics of coastal groundwater and river water is significant to delineate the scope of seawater intrusion and to determine the degree of influence.The purpose of the study was to analyze the changes of water chemistry in the process of seawater intrusion. To confirm the correlation, twenty three water samples were collected from aquifers of seawater intrusion of Changle and upstream movement area of Minjiang, which the conventional ion were tested at laboratory. By analyzing the relative changes between major ions and Cl ions with seawater dilution line, and comparing the ionic concentration difference between the actual and the ideal, the water chemical changes with seawater intrusion are investigated. The results were as follows: Types of water chemistry were followed by Na-Cl—Na-Cl·HCO₃—Na·Ca-HCO₃·Cl—Ca-HCO₃ as seawater mixed with freshwater; Increase of Na⁺，Cl^- was the main factor to affect the type of water chemistry and TDS; Content ofCa²⁺，Mg²⁺was higher than ideal concentration line and seawater dilution line，but Na⁺, K⁺ waved. The ratio curve ofBr^-/Cl^- was good agreement with seawater dilution line and can be used as one decisive factor to seawater intrusion.

Key words: seawater intrusion, hydrochemistry, mixed relationship, Changle