• 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 Mechanical Science and Technology
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• v.15 no.3
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• pp.327-338
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• 2001

This paper presents the results of a structural analysis to determine design variables such as the inner basket array type, and thicknesses of the outer shell, and lid and bottom of a spent nuclear fuel disposal canister. The canister construction type introduced here is a solid structure with a cast iron insert and a corrosion resistant overpack, which is designed for the spent nuclear fuel disposal in a deep repository in the crystalline bedrock, entailing an evenly distributed load of hydrostatic pressure from the groundwater and high swelling pressure from the bentonite buffer. Hence, the canister must be designed to withstand these high pressure loads. Many design variables may affect the structural strength of the canister. In this study, among those variables, the array type of inner baskets and thicknesses of outer shell and lid and bottom are attempted to be determined through a linear structural analysis. Canister types studied hear are one for the pressurized water reactor (PWR) fuel and another for the Canadian deuterium and uranium reactor (CANDU) fuel.

• Economic and Environmental Geology
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• v.50 no.6
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• pp.445-466
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• 2017

Yeongdong area is located in the contact zone between central southeastern Ogcheon belt and Yeongnam massif, in which Cretaceous Yeongdong basin exists. Therefore, the study area has complex geological environment of various geological age and rock types such as Precambrian metamorphic rocks, age-unknown Ogcheon Supergroup, Paleozoic/Mesozoic sedimentary rocks, Mesozoic igneous rocks and Quaternary alluvial deposits. This study focuses on the link between the various geology and water type, and discussed the source of some major ions and their related water-rock interaction. For this study, the field parameters and ion concentrations for twenty alluvial/weathered and eighty bedrock aquifer wells were used. Statistical analysis indicates that there was no significant differences in groundwater quality between wet and dry seasons. Although various types were observed due to complex geology, 80 to 84 % of samples showed $Ca-HCO_3$ water type. Some wells placed in alluvial/weathered aquifers of Precambrian metamorphic and Jurassic granitic terrains showed somewhat elevated $NO_3$ and Cl concentrations. $Mg-HCO_3$ typed waters prevailed in Cretaceous Yeongdong sedimentary rocks. The deeper wells placed in bedrock aquifers showed complicated water types varying from $Ca-HCO_3$ through $Ca-Cl/SO_4/NO_3$ to $Na-HCO_3$ and Na-Cl type. Groundwater samples with $Na-HCO_3$ or Na-Cl types are generally high in F concentrations, indicating more influences of water-rock interaction within mineralized/hydrothermal alteration zone by Cretaceous porphyry or granites. This study revealed that many deep-seated aquifer had been contaminated by $NO_3$, especially prominent in Jurassic granites area. Based on molar ratios of $HCO_3/Ca$, $HCO_3/Na$, Na/Si, it can be inferred that Ca and $HCO_3$ components of most groundwater in alluvial/weathered aquifer wells were definitely related with dissolution of calcite. On the other hand, Ca and $HCO_3$ in bedrock aquifer seem to be due to dissolution of feldspar besides calcite. However, these molar ratios require other mechanism except simple weathering process causing feldspar to be broken into kaolinite. The origin of $HCO_3$ of some groundwater occurring in Cretaceous Yeongdong sedimentary rock area seems to be from dissolution of dolomite($MgCO_3$) or strontianite($SrCO_3$) as well.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.519-519
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• 2003

We performed a hydrochemical study on a total of 89 bedrock groundwaters collected from preexisting wells (30 to 300 m deep) in the Boeun area. Hydrochemical data showed significant variations in the area, due to varying degrees of anthropogenic pollution. The waters were mostly enriched in Ca and HCO$_3$ but locally contained significant concentrations of anthropogenic constituents in the general order of Cl >NO$_3$>SO$_4$. In particular, about 11% of the examined wells exceeded the drinking water standard with respect to nitrate. We consider that aquifers in the area are locally highly susceptible to the contamination related to agricultural activities. Diagrams showing the relationships between the summation of cations (∑cations) and the concentration of several anions with different origin (natural versus anthropogenic) were used to estimate the relative role of anthropogenic contamination. A good correlation was observed for the relationship between ∑cations and bicarbonate, indicating that water-rock interaction (namely, hydrolysis of silicate minerals) is most important to control the water quality. Thus, we made an assumption that the equivalent of dissolved cations for a water should be equal to the alkalinity, if the chemistry were controlled solely by a set of natural weathering reactions. If we excluded the equivalent quantities of cations and bicarbonate (natural origin) from the acquired data for each sample, the remainder therefore could be considered to reflect the degree of anthropogenic contamination. Finally, we performed a multiple regression approach for hydrochemical data using the ∑cations as a dependent variable and the concentration data of each anion (natural or anthropogenic) as an independent variable. Using this approach, we could estimate the relative roles of anthropogenic and natural processes. Rather than the conventional evaluation scheme based on water quality criteria, this approach will be more useful and reasonable for the evaluation of groundwater quality in a specific region and also can be used for planning appropriate protection and remedial actions.

• The Journal of Engineering Geology
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• v.3 no.2
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• pp.149-165
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• 1993

Nowadays, the field hydraulic test is still an only method to evaluate groundwater characteristics in subsurface. The results of hydraulic test are very important for the concept model of fracture hydrogeology as well as the geometric pattern of fractures. The hydraulic tests performed in Korea are generally analysed under such assumption as steady radial flow in homogeneous aquifer or along simple geometry of fractures. Also the transmissivity measured in a fixed interval length is equivalent to a sum of individual fracture transmissivities in test legth. The boundary effects of weH hydraulics and the geometry of flow paths are hardly obtained from the test results analysed by a steady flow method. To circumvent this problem, the flow dimensional analysis was attempted from the results of constant pressure injection test carried out in a fractured granite area. A comparison of the hydraulic conductivity values from the transient and steady analysis shows that the latter is about a factor of 2~3 higher than the former. However, it was possible to analyse a flow dimension of each test interval from flow rate variation with time. The upper part of the bedrock(<10m deep) indicates an open boundary and the flow dimension shows nearly steady states, while the lower part of the bedrock(>25m deep) is characterized as sublinear flow dimension with a dosed boundary. In one of the test sections(15m deep), the flow dimension was changed from linear flow to spherical flow. From the experience of this study, one of the immediate problems to be solved is to enhance the field testing equipments, i.e., an accurate flowmeter with autorecording and a pressure detecting device to be able to install in the test section.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.10a
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• pp.70-86
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• 2003

Despite its usability, TCE has been managed as a hazardous material due to the toxicity and many contamination cases were surveyed in some developed countries. U.S.EPA(Kram et al., 2001) suggested DNAPL characterization methods and approaches based on survey experiences at several sites. However, Korea has not the least assessment of contamination and trial of remediation, although there are a lot of doubtable areas where ground water would be contaminated with TCE. In this study, we try to assess the volume and extent of ground water contamination with TCE and delineate the contamination source zones in an industrial area. Ground water in this area flows through fractures and the contaminant TCE has the properties of high volatility, high density and low partitioning to soil material. Thus, we applied a variety of technical approaches to identify the contamination status; documentary, hydrogeochemical, hydrogeological and geological surveys. In addition, additional survey was performed based on the interim findings, which showed that ground water contamination was limited to the relatively small area with high concentrations to the deep place. The contamination source zone is estimated to be the asphalt test institute where a great deal of TCE has been used to analyze the amount of asphalt soluble in TCE since 1984. Based on the contamination characterization and a myriad of documents about ground water remediation, appropriate site remediation management options will be recommended later. This study is now under way and this paper was focused on describing the technical approaches used to achieve the goals of this study.

• The Journal of Engineering Geology
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• v.26 no.2
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• pp.261-276
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• 2016

The occurrence of natural radioactive materials such as uranium and radon-222 in groundwater was examined with hydrogeochemistry and geology at ○○ village in the Yongin area. Two rounds of 19 groundwater and 5 surface water sampling were collected for analysis. The range of pH value in groundwaters was 5.81 to 7.79 and the geochemical types of the groundwater were mostly Ca(Na)-HCO₃ and Ca(Na)-NO₃(Cl)-HCO₃. Uranium and radon-222 concentrations in the groundwater ranged from 0.06 to 411 μg/L and from 5.56 to 903 Bq/L, respectively. Two deep groundwaters used as common potable well-water sources exceeded the maximum contaminant levels of the uranium and radon-222 proposed by the United States Environmental Protection Agency (US EPA). Three groundwater samples from residential areas contained unsuitable levels of uranium, and 12 groundwater samples were unsuitable due to radon-222 concentrations. Radioactive materials in the unsuitable groundwater are naturally occurring in a Jurassic amphibole- and biotite-bearing granitic gneiss. High uranium and radon-222 groundwater concentrations were only observed in two common wells; the others showed no relationship between bedrock geology and groundwater geochemical constituents. With such high concentrations of naturally occurring radioactive materials in groundwater, the affected areas may extend tens of meters for uranium and even farther for radon-222. Therefore, we suggest the radon-222 and the uranium did not originate from the same source. Based on the distribution of radon-222 in the study area, zones of higher radon-222 concentrations may be the result of diffusion through cracks, joint, or faults. Surface radioactivity and uranium concentrations in the groundwater show a positive relationship, and the impact areas may extend for ~200m beyond the well in the case of wells containing high concentrations of uranium. The highest uranium and thorium concentrations in rock samples were detected in thorite and monazite.

• Economic and Environmental Geology
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• v.41 no.6
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• pp.645-655
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• 2008

The Cr(VI) concentrations at the shallow aquifer well (MPH-0-1) of the Moonpyung groundwater monitoring station were in the range of 0.5 to 3.1 mg/L exceeding 10 to 62 times the guideline for drinking-water quality, indicating continuous contamination. However, Cr was not detected at the deep bedrock well and the other subsidiary monitoring wells except for MPH-1 and 6. Cross-correlation analyses were conducted for rainfall and groundwater level time series, resulting in the mean time of recharge after precipitation events to be 5.6 days. For rainy season, the water level was raised and the Cr(VI) concentration was several times lower than that during dry season at well MPH-0-1 well. Correlation of the Cr(VI) concentration with the groundwater-level showed that the Cr(VI) reduction was closely related with the groundwater-level rise in the well. However, the groundwater level rise during high water season induced the lateral migration of the Cr(VI)-contaminated groundwater at well MPH-4. We enriched and isolated a chromium reducing bacteria, Enterobacter aerogenes, from the Cr(VI)-contaminated groundwater in the wells MPH-0-1 and MPH-1. The bacteria may play an important role for immobilizing Cr(VI) in the Cr(VI)-contaminated groundwater. Therefore, the migration of the contaminant (Cr(VI) must has been restricted because of the natural attenuation by microbial reduction of Cr(VI) in the groundwater. This research suggests that the bioremediation of the Cr(VI)-contaminated groundwater by the indigenous bacteria may be feasible in the Cr(VI) contaminated groundwater.

• Economic and Environmental Geology
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• v.40 no.4
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• pp.403-418
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• 2007

The objective of this research was to characterize the fate and transport of Cr(VI) contaminated groundwater in the Daejeon industrial area. Five subsidiary monitoring wells were newly installed and two existing wells were utilized for the investigation and the reduction process of Cr(VI) contaminated groundwater of the Daejeon(Mun-pyeong) national groundwater monitoring station. The Cr(VI) concentrations at the shallow aquifer well of the station were in the range of 3.2-4.5 mg/L indicating continuous contamination. However, Cr was not detected at the deep bedrock well and the other monitoring wells except MPH-1 and 3. The Cr(VI) concentrations of MPH-1 and MPH-3 were below the drinking water guideline value (0.05 mg/L). Therefore, the plume of the Cr(VI) contaminated groundwater was predicted to be confined within the narrow boundary around the station. The soluble/exchangeable Cr(VI) concentrations were below the detection limit in all core and slime samples taken from the five newly installed wells. Although the exact source of contamination was not directly detected in the study area, the spatial Cr(VI) distribution in groundwater and characteristics of the core samples indicated that the source and the dispersion range were confined within the 100 m area from the monitoring station. The contamination might be induced from the unlined landfill of industrial wastes which was observed during the installation of an subsidiary monitoring well. For the evaluation of the natural attenuation of Cr(VI), available reduction capacities of Cr(VI) with an initial concentration of 5 mg/L were measured in soil and aquifer materials. Dark-gray clay layer samples have high capacities of Cr(VI) reduction ranging from 58 to 64%, which is obviously related to organic carbon contents of the samples. The analysis of reduction capacities implied that the soil and aquifer materials controlled the dispersion of Cr(VI) contamination in this area. However, some possibilities of dispersion by the preferential flow cannot be excluded due to the limited numbers of monitoring wells. We suggest the removal of Cr(VI) contaminated groundwater by periodical pumping, and the continuous groundwater quality monitoring for evaluation of the Cr(VI) dispersion should be followed in the study area.