• The Journal of Engineering Geology
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• v.31 no.4
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• pp.647-658
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• 2021

In this study, the change of temperature, chemical composition, and helium gas of thermal water in Pohang area was observed from January 2018 to June 2019 in order to interpret the relationship with earthquake events. During observation period earthquakes above M 2.0 within 100 km in a radius from a geothermal well occurred 58 including two earthquake events with a magnitude of 3.0~3.9 and two earthquake events with a magnitude of 4.0~4.9. We introduce a q-factor and earthquake effectiveness (ε) to express the influence of each earthquake as magnitude and distance factors. The geothermal well of 715 m deep was developed in the Bulguksa biotite granite, and the water temperature was observed in the variation from 51.8 to 56.3℃ during monitoring period. At M 4.1 and M 4.6 earthquake events, the increase of geothermal water temperature (𝜟T 2.6~4.5℃) was recorded, and slight change in specific ionic components such as SO₄ and Cl, and of chemical types on the Piper diagram were observed. In the ³He/⁴He vs ⁴He/²⁰Ne diagram, the original mixing ratio of helium isotope before and after the magnitude 4.1 earthquake was slightly changed from 83.0% to 83.2% of crust-origin ⁴He, and the from 16.3% to 16.7% of mantle-origin ³He. Hot-cold water mixing ratio before and after earthquakes by using the quartz and chalcedony solubility curves of the silica-enthalpy mixing model was calculated to interpret the temperature change of geothermal water. The model calculation shows the increase of 6.93~7.72% and 1.65~4.94% of hot water ratio at E1 and E2 earthquakes, respectively. Conclusively, the magnitude of earthquake for observable change in the temperature and helium isotope of thermal water is of 4.1 or higher and q-factor value of 30.0 or higher in the study site.

• The Journal of Engineering Geology
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• v.19 no.2
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• pp.235-250
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• 2009

Environmental elements such as B, Br, and Sr in groundwater from Bukahn-myeon, Yeongcheon, Gyeongbuk Province, were investigated in order to know their origin with emphasis on hydrochemistry. pH ranges from 7.37 to 8.39. B content is 0.41${\sim}$4.62 mg/L with an average 1.74 mg/L and Br content is 0${\sim}$3.24 mg/L with an average 2.22 mg/L, and Sr content is 0.93${\sim}$8.64 mg/L with an average 2.76 mg/L. The water types plotted by the Piper diagram are different but mostly $Ca-HCO_3$. Some constituents contributing to EC are Na, $SO_4$, Cl with high determinative coefficients($R^2$) of 0.85, 0.70, 0.90, respectively. The coefficients($R^2$) of Cl to Na, K, $SO_4$ are 0.54, 0.68, 0.53, respectively. It should be noted that there are high cocfficients($R^2$) of B-Sr and $Sr-SO_4$ with 0.65, 0.64, respectively. The Cl/Br ratios are 5.21${\sim}$30.70 due to significant depletion of Cl. The $SO_4/Cl$ ratios are 1.32${\sim}$27.24 with an average of 5.92, ascribed to abundant introduction of $SO_4$ or significant depletion of Cl. Chemical speciation calculated shows that B exists mostly as $H_3BO_3$ with less $H_2BO^-_3$ and Br exists as only $Br^-$. Sr exists mostly as $Sr^2$ with less $SO_4$. Saturation index represents that goundwater is supersaturated with respect to barite, kaolinite, illite, K-mica, and smectite while it is slightly undersaturated with respect to silica, gypsum, anhydrite, talc, chrysotile, feldspar, kaolinite, illite, K-mica, and smectite. The saturation index of celestine is -2.23${\sim}$-0.13 indicating more Sr can be incorporated into groundwater. Groundwater is still much undersaturated to halite. It is likely that the origin of S and Sr was related to the Yucheon volcanic rocks. Br might be originated from the local geological features with introduction of anthropogenic matters.

• The Journal of Engineering Geology
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• v.23 no.4
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• pp.477-491
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• 2013

Natural radionuclides in groundwater in the Danyang area were investigated to characterize the behaviors of uranium and radon with respect to lithology and physico-chemical components, which can aid our understanding of their occurrence, properties, and origins. To this end, a total of 100 groundwater samples were collected and analyzed, and radionuclide levels were used to construct detailed concentration maps. The water type of the groundwater, assessed using a Piper diagram, is mainly Ca-Na-$HCO_3$. The concentrations of uranium range from 0.02 to $251.0{\mu}g/L$ (average, $3.85{\mu}g/L$) and only 1% exceed USEPA's MCL (Maximum Contaminant Level). Uranium is enriched in groundwaters of Cretaceous granites and Precambrian metamorphic rocks, whereas it is depleted in groundwaters of sedimentary rocks. The concentrations of radon range from 13 to 28,470 pCi/L (average, 2397 pCi/L). Only 15% of the samples exceed AMCL (Alternative Maximum Contaminant Level) of 4000 pCi/L. The radon concentration is highest in groundwater of Cretaceous granites and lowest in groundwater of sedimentary rocks. In conclusion, the distribution and occurrence of radionuclides are intimately related to the basic geological characteristics of the rocks in which the radiogenic minerals are primarily contained. The behavior of uranium is only weakly related to that of radon (correlation coefficient = 0.15). There are also weak correlations between radionuclides and the main chemical components, pH, EC, Eh, and well depth. Of note, the correlation coefficient between radon and $SiO_2$ is 0.68, and that between radon and $HCO_3$ is -0.48. Factor analysis shows that radionuclides behave somewhat independently of each other because there are no significant factors that control the behavior of chemical components as well as radionuclides. The detailed concentration maps during this study will be used to establish useful database of radionuclide distribution and geological properties throughout Korea.

• Economic and Environmental Geology
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• v.42 no.6
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• pp.599-608
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• 2009

This study was conducted to examine chemical characteristics and correlations among seepage water, subsurface waters and inland groundwater in and around a coastal underground LPG cavern using factor and cluster analyses. The study area is located in western coast of Incheon metropolitan city and is about 8 km off the coast. The LPG cavern storing propane and butane was built beneath artificially reclaimed island. Mean bathymetry is 8.5 m and maximum sea level change is 10 m. Water sampling was conducted in May and August, 2006 from 22 sampling points. Correlation analysis showed strong correlations among $Fe^{2+}$ and $Mn^{2+}$ (r=0.83~0.99), and Na and Cl (r=0.70~0.97), which indicated reductive dissolution of iron and manganese bearing minerals and seawater ingression effect, respectively. According to factor analysis, Factors 1 (May) and I (August) showed high loadings for parameters representing seawater ingression into the cavern and effect of submarine groundwater discharge, respectively while Factors 2 and IV showed high loadings for those representing oxidation condition (DO and ORP). Factors 4 and II have large positive loadings for $Fe^{2+}$ and $Mn^{2+}$. The increase of $Fe^{2+}$ and $Mn^{2+}$ was related to decomposition of organic matter and subsequent their dissolution under reduced condition. Cluster analysis showed the resulting 6 groups for May and 5 groups for August, which mainly included groups of inland groundwater, cavern seepage water, sea water and subsurface water in the LPG storage cavern. Subsurface water (Group 2 and Group III) around the underground storage cavern showed high EC and major ions contents, which represents the seawater effect. Cavern seepage water (Group 5 and Group II) showed a reduced condition (low DO and negative ORP) and higher levels of $Fe^{2+}$ and $Mn^{2+}$.

• Economic and Environmental Geology
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• v.42 no.6
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• pp.527-539
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• 2009

The Kumho River flows through volcanic and sedimentary rocks at upstream and downstream regions and also through industrial district including dyeing complex before it meets the Nakdong River, and as a result, many factors can influence the geochemistry of river water. The concentrations of dissolved ions generally increased as it flows downstream. The concentrations of cations are in the order of Ca>Na>Mg>K, and those of anions are $HCO_3$>$SO_4$>Cl>$NO_3$. These results show that the weathering of sandstone and shale containing carbonate including calcite caused the enrichment of Ca and $HCO_3$. At first 4 sampling sites, Si contents are relatively high mainly due to the weathering of silicate minerals of volcanic rocks. However, Na and $SO_4$ contents are higher at downstream sites due to the industrial and municipal sewage. Piper diagram also shows that the geochemical patterns changed from Ca-$HCO_3$ to Ca-Cl/Ca-$SO_4$ and Na-Cl/Na-$SO_4$ type. When comparing the samples collected in May and July, the concentrations of dissolved ions in July are generally lower than those in May, which indicates that dilution by precipitation played an important role. In July the relative concentration of Ca increased, indicating that Ca in soils probably from fertilizer were mixed into the river water by precipitation. The river waters are mainly from precipitation. The dissolved ions are mainly from weathering of carbonate minerals and pollutants from municipal sewage and discharged water from industrial complex. The composition of oxygen and deutrium isotope in July showed higher values, which is contrary to the amount effect, maybe due to Youngchon Dam. The nitrogen isotope showed lower values in July than those in May, which can be interpreted to indicate mixing of nitrate from soils and fertilizer in the cultivated land by the heavy rain. The isotope composition of nitrate increased downstream, indicating that the influence of sewage and animal manure also increased downstream.

• Economic and Environmental Geology
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• v.41 no.1
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• pp.47-56
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• 2008

pH and Eh were measured at 25 points in the abandoned Dalcheon mine. And, major ion components $(Na^+,\;K^+,\;Ca^{2+},\;Mg^{2+},\;Cl^-,\;SO_4^{2-},\;CO_3^{2-},\;HCO_3^-)$ were analyzed through groundwater sampling at 41 points. pH and Eh were measured the highest concentration in serpentinite area. And, pH was between weak alkaline and intermediate values in study area. Groundwater in study area was dominated oxidation-reduction environment caused by reaction with carbonate rock. Because sulfur components contained in carbonate, serpentinite, arsenopyrite and pyrite was dissolved by groundwater, $SO_4^{2-}$ component was high in study area. And $Ca^{2+},\;Mg^{2+}$ of cations were high. Correlation coefficients of ion components in tailing dumps were 0.95 between $Ca^{2+}\;and\;SO_4^{2-}$, 0.86 between $Ca^{2+}\;and\;Mg^{2+}$, 0.85 between $Mg^{2+}\;and\;SO_4^{2-}$. Correlation coefficients of ion components in bedrock were 0.86 between $Mg^{2+}\;and\;SO_4^{2-}$, 0.68 between $Ca^{2+}\;and\;SO_4^{2-}$. Concentration range of $Ca^{2+}$ in tailing dumps was $6.85{\sim}323.58mg/L,\;and\;3.18{\sim}207.20mg/L$ in bedrock. Concentration range of $SO_4^{2-}$ in tailing dumps was $21.54{\sim}1673.17mg/L,\;and\;2.04{\sim}1024.64mg/L$ in bedrock. By the result of Piper diagram analysis with aquifer material, groundwater in tailing dumps was $Ca-SO_4$ type. Groundwater quality types with bedrock material were Mg-$SO_4$ and Mg-$HCO_3$ types in serpentinite area, Ca-$HCO_3$ type in carbonate area, Na-K and $CO_3+HCO_3$ types in hornfels, respectively. As a result of this study, groundwater in tailing dumps were dissolved $Ca^{2+},\;Mg^{2+}\;and\;SO_4^{2-}$ components with high concentration. Also, these ion components were transported into bedrock aquifer.

• The Journal of Engineering Geology
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• v.24 no.4
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• pp.551-574
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• 2014

The occurrence, distribution, and hydrogeochemical characteristics of uranium and radon in groundwater within different lithologies in Gyeongnam and Gyeongbuk provinces were investigated. A total of 201 groundwater samples from sedimentary rocks taking a large portion of the geology and from igneous rocks taking a small portion of the geology were analyzed and examined using factor analysis. Their radionuclide levels were used to construct detailed concentration maps. The groundwater types, defined using a Piper diagram, are mainly Ca-$HCO_3$ with less Na-$HCO_3$. Among the samples, one site exceeds $30{\mu}g/L$ of uranium (i.e., the maximum contaminant level of the USEPA) and three sites exceed 4,000 pCi/L of radon (i.e., the alternative maximum contaminant level). No samples were found to exceed the 15 pCi/L level of gross alpha or the 5 pCi/L level of radium. The concentration of uranium ranges from 0.02 to $53.7{\mu}g/L$, with a mean of $1.56{\mu}g/L$, a median of $0.47{\mu}g/L$, and a standard deviation of $4.3{\mu}g/L$. The mean concentrations of uranium for the different geological units increase in the following order: Shindong Group, Granites, Hayang Group, Yucheon Group, and Tertiary sedimentary rocks. The concentration of radon ranges from 2 to 8,740 pCi/L, with an mean of 754 pCi/L, a median of 510 pCi/L, and a standard deviation of 907 pCi/L. The mean radon concentrations for the investigated geological units increase in the following order: Granites, Yucheon Group, Tertiary sedimentary rocks, Hayang Group and Shindong Group. According to the factor analysis for each geological unit, uranium and radon behave independently of each other with no specific correlation. However, radionuclides show close relationships with some components. Regional investigations of radionuclides throughout the country require an integrated approach that considers the main lithological units as well as administrative districts.

• The Journal of Engineering Geology
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• v.18 no.4
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• pp.555-566
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• 2008

Hydrogeochemical study in Samseung area (Boeun, Chungbuk) and waterrock interaction experiment using rock samples from the area were performed to elucidate the fluoride source in groundwater and explaining geochemical behavior of fluoride ion. Fluoride concentration of public water supply mostly using groundwater in Boeun area was significantly higher in South Korea. The maximum fluoride concentration of the study area was 3.9 mg/L, and 23% of samples exceeded the Korean Drinking Water Standard of fluoride (1.5 mg/L). The average concentration of fluoride was 1.0 mg/L and median was 0.5 mg/L. Because of high skewness (1.3), median value is more appropriate to represent fluoride level of this area. The relationships between fluoride ion and geochemical parameters ($Na^+$, $HCO_3$, pH, etc.) indicated that the degree of waterrock interaction was not significant. However, high fluoride samples were observed in $NaHCO_3$ type on Piper's diagram. The negative relationship between fluoride and $NO_3$ ion which might originate from surface contaminants was obvious. These results indicate that fluoride ion in groundwater is geogenic origin. The source of fluoride was proved by waterrock interaction batch test. Fluoride concentration increased up to 1.2 mg/L after 96 hours of reaction between water and biotite granite. However, the relationship between well depth and fluoride ion, and groundwater age and fluoride ion was not clear. This indicates that fluoride ion is not correlated with degree of waterrock interaction in this area but local heterogeneity of fluoriderich minerals in granite terrain. High fluoride concentration in Boeun area seems to be correlated with distribution of permeable structures in hard rocks such as lineaments and faults of this area. This entails that the deep bedrock groundwater discharges through the permeable structures and mixed with shallow groundwater.

• Journal of the Korean Society of Groundwater Environment
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• v.6 no.3
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• pp.140-151
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• 1999

Groundwater samples from the southern area composed of andesitic rocks and the northwestern area composed of granite in Pusan city, have been collected and analyzed. According to the Piper diagram. groundwater in the southern area belongs to Ca$\^$2＋/－HCO$_3$$\^$－/ and Ca$\^$2＋/－(Cl$\^$－/＋SO$_4$$\^$2－/) types, and that in the northwestern area mostly belongs to Ca$\^$2＋/－HCO$_3$$\^$－/ type and partly Na$\^$＋/－HCO$_3$$\^$－/ type. Two factors (factor 1 and factor 2) were obtained from the result of the factor analysis in the southern area. Factor 1, consisting of Mg$\^$2＋/, Ca$\^$2＋/, Cl$\^$－/, SO$_4$$\^$2－/, NH$_4$$\^$＋/, EC and NO$_3$$\^$－/ is represented by the dissolution of Ca-plagioclase and calcite, and the influence of anthropogenic sources. Factor 2, consisting of K$\^$＋/, Na$\^$＋/. SiO$_2$, SO$_4$$\^$2－/, and HCO$_3$$\^$－/ is mainly represented by the dissolution of feldspar. Three factors were obtained from the result of the factor analysis in the northwestern area Factor 1, consisting of Na$\^$＋/, K$\^$＋/, NH$_4$$\^$＋/, Cl$\^$－/, SO$_4$$\^$2－/ and NO$_3$$\^$－/ explains dissolution of plagioclase and mica, the influence of anthropogenic sources and salt water. Factor 2, consisting of Ca$\^$2＋/ and HCO$_3$$\^$－/ explains the dissolution of Ca-plagioclase. Factor 3, consisting of Mg$\^$2＋/ and SiO$_2$, explains the dissolution of silicate minces. and contaminants. Based on the phase stability diagrams, groundwater both in the southern and in the northwestern area is mostly in equilibrium with kaolinite. Cl$\^$－/ with respect to Na$\^$＋/, Ca$\^$2＋/, Mg$\^$2＋/, K$\^$＋/, SO$_4$$\^$2－/ and HCO$_3$$\^$－/ indicates that both the northwestern area and the southern area are influenced by the salt water.

• Economic and Environmental Geology
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• v.40 no.5
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• pp.635-649
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• 2007

Geochemical composition, stable isotopes $({\delta}^{18}O,\;{\delta}D,\;{\delta}^{34}S)$ and noble gases(He, Ne and Ar) of nine hot spring water and three groundwater for five hot springs(Jukam, Hwasun, Dokog, Jirisan, Beunsan) from the Honam area were analyzed to investigate the hydrogeochemical characteristics and the hydrogeochemical evolution of the hot spring waters, and to interpret the source of sulfur, helium and argon dissolved in the hot spring waters. The hot spring waters show low water temperature ranging from 23.0 to $30.5^{\circ}C$ and alkaline characteristics of pH 7.67 to 9.98. Electrical conductivity of hot spring waters is $153{\sim}746{\mu}S/cm$. Groundwaters in this area were characterized by the acidic to neutral pH range$(5.85{\sim}7.21)$, the wide electrical conductivity range $(44{\sim}165{\mu}S/cm)$. The geochemical compositions of hot spring and groundwaters can be divided into three water types: (1) $Na-HCO_3$ water type, (2) Na-Cl water type and (3) $Ca-HCO_3$ water type. The hot spring water of $Ca-HCO_3$ water type in early stage have been evolved through $Ca(Na)-HCO_3$ water type into $Na-HCO_3$ type in final stage. In particular, Jurim alkaline(pH 9.98) hot spring water plotted at the end point of $Na-HCO_3$ type in the Piper diagram is likely to arrive into the final stage in geochemical evolution process. Hydrogen and oxygen isotopic data of the hot spring water samples indicate that the hot spring waters originated from the local meteoric water showing latitude and altitude effects. The ${\delta}^{34}S$ value for sulfate of the hot spring waters varies widely from 0.5 to $25.9%o$. The sulfur source of most hot spring waters in this area is igneous origin. However, The ${\delta}^{34}S$ also indicates the sulfur of JR1 hot water is originated from marine sulfur which might be derived ken ancient seawater sulfates. The $^3He/^4He\;and\;^4He/^{20}Ne$ ratios of the hot spring waters range from $0.0143{\times}10^{-6}\;to\;0.407{\times}10^{-6}\;and\;6.49{\sim}584{\times}10^{-6}$, respectively. The hot spring waters are plotted on the mixing line between air and crustal components. It means that the He gas in the hot spring waters was mainly originated from crustal sources. However, the JR1 hot spring water show a little mixing ratio of the helium gas of mantle source. The $^{40}Ar/^{36}Ar$ ratios of hot spring water are in the range from $292.3{\times}10^{-6}\;to\;304.1{\times}10^{-6}$, implying the atmospheric argon source.