Chemical Characteristics of Groundwater in Carbonate Rock Areas of Korea

초록

This study was conducted to understand the chemical characteristics of groundwater in carbonate areas of Korea. In thisstudy, data on pH, electric conductivity (EC), Ca2+, Mg2+, Na+, K+, Cl−, SO42−, and HCO3− were collected from 97 wellswhich were installed in various carbonate rock regions of Korea. The pH values ranged from 5.7 to 9.9, and the averagevalue was 7.3. The concentration range showed differences between the maximum value of HCO3− and the medium tominimum values of Ca2+, Mg2+, Na+, Cl−, SO42−, and K+ in the study area. The average value of EC was 374 μS/cm,higher than in granite and gneiss areas, where the value is 176 μS/cm. Most of the groundwater was type Ca-HCO3, andsome was type Mg-HCO3. The relationship between Ca2+, Cl−, and HCO3−, respectively, and EC showed relativelysignificant positive correlations compared to the other dissolved components. However, the determination coefficients forMg2+, Na+, SO42−, and K+ were very low less than 0.2. These results indicate that the source of Ca2+ and Mg2+ is relativelysimple (carbonate dissolution) compared to other sources. The sources of Na+, K+, Cl−, SO42−, and HCO3− might be notonly water-rock interactions, but also irrigation return flow, because many groundwater wells had been developed forirrigation purposes. Subsequently, the influence of agriculture on groundwater chemistry was evaluated using a cumulativeplot of SO42−. The threshold value of SO42− calculated from the cumulative frequency curve was 29.2 mg/L. Therefore,12.4% of all the groundwater wells were affected by agricultural activity.

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