THE CHARACTERISTICS OF GROUNDWATER QUALITY USING HYDROGEOCHEMICAL ANALYSIS AT THE GIMHAE CITY, KOREA

Groundwater and surface water were analyzed to understand the hydrogeochemical characteristics of groundwater at the Gimhae City in Korea. Trilinear diagram showed that CaHCO₃ type (53%) was the most predominant, and CaCl₂ type (39.2%) and NaCl type (7.8%) were dominant in order. The main components of groundwater contamination were Cl^- from saline water, and NO₃-N from sewage, livestock and fertilizer. The origin of NO₃-N was estimated from the nitrogen isotope ratio δ¹⁵N. The main source of nitrogen was municipal sewage and livestock. Groundwater was classified into 4 groups using the background concentration of Cl^- and NO₃-N extracted from Sinclair′s method (1974). The background concentration was 61.2 mg/L for Cl^- and 9.1 mg/L for NO₃-N. The influence of groundwater from saline water was examined by Cl/HCO₃ ratio, Na/Cl ratio, Br/Cl ratio, and SO₄/Cl ratio. Cl/HCO₃ ratio showed that 52.8% of groundwater was fresh water, and 24.9% of groundwater was contaminated by saline water. The Na/Cl ratio was 1.53 in average, and was much higher than the average ratio 0.85 (Cho et al., 2003) of seawater. The Br/Cl ratio was 39.1X10^-4 in average, and was higher than the average ratio 34.7X10^-4 (Morris and Riley, 1966) of seawater. The SO₄/Cl ratio was 0.1546 in average, and was much higher than the average ratio 0.1050 (Steinkampf, 1982) of seawater. Hydrogen and Oxygen Isotope Ratio was used for the identification of groundwater origin. The hydrogen isotope ratio δD was from -62.0 to -32.7, and the oxygen isotope ratio δ¹⁸O was from -8.8 to -5.4. The data of Hydrogen and Oxygen Isotope Ratio were very close to meteoric water line (δD = 8δ¹⁸O + 10) of Craig (1961), and indicated that the groundwater of study area came from the meteoric water. Therefore, It was concluded that the origin of chloride was not directly from the sea, but from the old residual saline water.