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
/
v.4
no.1
/
pp.41-53
/
1997
Geochemical data of soil and water samples were presented in order to assess the environmental impart for drinking water sites. Microscopic observation of rock samples and physical and chemical analysis of soil and water samples were undertaken. The geology of study areas are classified into three groups such as granitic rocks, meta-sedimentary rocks and sedimentary rocks. Enrichment of heavy metals derived from those rocks is not found in this study areas. Soils were analyzed for Cu, Pb, Zn, Cd and Cr using AAS extracted by HNO$_3$+HClO$_4$ and 0.1 N HCl. Heavy metal concentrations in soils are within the range of those in uncontaminated soils. In comparison of metal contents extracted by 0.1 N HCl and HNO$_3$+HC1O$_4$, less than 10% of the heavy metals are present in the exchangeable fraction. In particular, an pollution index has been proposed to assess the degree of soil contamination. Pollution index in soils are between 0.03 and 0.47 therefore, soils are not polluted with heavy metals. Deep groundwaters within granitic rocks have been evolved into Na$\^$+/-HCO$_3$$\^$-/ type, whereas other deep groundwaters evolved into Ca$\^$2+/-HCO$_3$$\^$-/ type. The predominance of Na$\^$+/ over Ca$\^$2+/ in deep groundwaters within granitic rocks is a result of dissolution of plagioclase, but for sedimentary and meta-sedimentary rocks, dissolution of calcite is a dominant factor for their hydrogeochemistry. The pH, conductivity and contents of the most dissolved ions in the water increase with depth. Shallow groundwaters, however, are highly susceptible to pollution owing to agricultural activities, considering the fact that high contents of nitrate, chloride and potassium, and high K/Na ratio are observed in some shallow groundwaters. In a thermodynamic approach, most natural water samples are plotted within the stability fields of kaolinite and smectite. Therefore, microcline and other feldspars will alter to form clay minerals, such as kaolinite and smectite. From the modelling for water-rock interactions based on mass balance equation, models accord well with behavior of the ions and results of thermodynamic studies are derived.
Journal of the Korean Society of Groundwater Environment
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v.7
no.3
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pp.103-115
/
2000
The formation of brown-colored precipitates is one of the serious problems frequently encountered in the development and supply of groundwater in Korea, because by it the water exceeds the drinking water standard in terms of color. taste. turbidity and dissolved iron concentration and of often results in scaling problem within the water supplying system. In groundwaters from the Pajoo area, brown precipitates are typically formed in a few hours after pumping-out. In this paper we examine the process of the brown precipitates' formation using the equilibrium thermodynamic and kinetic approaches, in order to understand the origin and geochemical pathway of the generation of turbidity in groundwater. The results of this study are used to suggest not only the proper pumping technique to minimize the formation of precipitates but also the optimal design of water treatment methods to improve the water quality. The bed-rock groundwater in the Pajoo area belongs to the Ca-$HCO_3$type that was evolved through water/rock (gneiss) interaction. Based on SEM-EDS and XRD analyses, the precipitates are identified as an amorphous, Fe-bearing oxides or hydroxides. By the use of multi-step filtration with pore sizes of 6, 4, 1, 0.45 and 0.2 $\mu\textrm{m}$, the precipitates mostly fall in the colloidal size (1 to 0.45 $\mu\textrm{m}$) but are concentrated (about 81%) in the range of 1 to 6 $\mu\textrm{m}$in teams of mass (weight) distribution. Large amounts of dissolved iron were possibly originated from dissolution of clinochlore in cataclasite which contains high amounts of Fe (up to 3 wt.%). The calculation of saturation index (using a computer code PHREEQC), as well as the examination of pH-Eh stability relations, also indicate that the final precipitates are Fe-oxy-hydroxide that is formed by the change of water chemistry (mainly, oxidation) due to the exposure to oxygen during the pumping-out of Fe(II)-bearing, reduced groundwater. After pumping-out, the groundwater shows the progressive decreases of pH, DO and alkalinity with elapsed time. However, turbidity increases and then decreases with time. The decrease of dissolved Fe concentration as a function of elapsed time after pumping-out is expressed as a regression equation Fe(II)=10.l exp(-0.0009t). The oxidation reaction due to the influx of free oxygen during the pumping and storage of groundwater results in the formation of brown precipitates, which is dependent on time, $Po_2$and pH. In order to obtain drinkable water quality, therefore, the precipitates should be removed by filtering after the stepwise storage and aeration in tanks with sufficient volume for sufficient time. Particle size distribution data also suggest that step-wise filtration would be cost-effective. To minimize the scaling within wells, the continued (if possible) pumping within the optimum pumping rate is recommended because this technique will be most effective for minimizing the mixing between deep Fe(II)-rich water and shallow $O_2$-rich water. The simultaneous pumping of shallow $O_2$-rich water in different wells is also recommended.
The Geochemica] and isotope studies on the $CO_2$-rich water from the Shinchon area were carried out. The Shinchon $CO_2$-rich water belongs to Ca(Na)-$HCO_3$ type showing very high $P_{CO_{2}}$ ( $10^{-0.35}$ ~ $10^{0.29}$ atm) and TDS (835-3,144 mg/L). The results of geochemical and isotope analysis indicate that $CO_2$ gas is originated from the deep seated source such as mantle or magmatic gases. The $CO_2$-rich water was evolved by interaction with deep-seated granite and major water-rock interaction was dissolution of p]agioclase resulting high Na content of $CO_2$-rich water. Precipitation and dissolution of secondary calcite might be accompanied with the dissolution of plagioclase maintaining Na/Ca ratio. High contents of K and $SO_4$ indicate that the geochemical characteristics of $CO_2$-rich water were partially affected by interaction with upper sedimentary rock during uprising to surface. N03 and tritium contents suggest that the $CO_2$-rich water was mixed with low $CO_2$ groundwater at some locations. The oxygen-hydrogen isotopes show that all water samples were derived from meteoric waters and the $CO_2$-rich water was isotopically re-equilibrated with lighter $CO_2$ gas. Although some carbon isotope data show isotopically heavy values, carbon isotope data indicate that the $CO_2$ gas was possib]y derived by deep source.
The geothermal waters from the Busan area belong to Na-CI type and are characterized by much higher EC (921 ~6,520${\mu}$S/cm) and TDS (608-3,390 mg/L) than other geothermal waters in Korea. The concentration of majorions shows a weakly positive relationship with temperature except for Mg ion. The concentrations of the major cat ions have the order of Na>Ca>K>Mg. Ca ion is enriched and Mg ion is depleted compared with seawater. All Br concentrations of geothermal water are lower than those of seawater, showing a positive relationship with temperature. Generally geochemical characteristics of geothermal waters of the Busan area indicate that these waters have relatively increased Ca and Sr contents and depleted Mg, Na and K contents caused by seawater interaction with wall rock at depth during deep circulation of seawater. Base on the relationship between major ions and temperature, saline geothermal waters are diluted and are cooled by mixing of groundwaters during ascent. Isotope study and reaction path modeling of the overall geochemical system are required in order to better quantify the evolution and origin of geothermal waters in the Busan area.
Journal of the Computational Structural Engineering Institute of Korea
/
v.14
no.4
/
pp.515-523
/
2001
In this paper results of a linear structural analysis for design and dimensioning of disposal containers for spent pressurized water reactor nuclear fuel and spent Canadian deuterium and uranium reactor nuclear fuel are presented. The container structure studied here is a solid structure with a cast insert and a corrosion resistant outer shell, which is designed for the spent nuclear fuel disposal in a deep repository. An evenly distributed load of hydrostatic pressure from the groundwater and large swelling pressure from the bentonite buffer are applied on the container. Hence, the container must be designed to endure these large pressure loads. In this study, the array type of inner baskets and thicknesses of outer shell and lid/bottom are attempted to be determined through a linear static structural analysis.
The deep environment and geochemical evolution of the Bugok geothennal waters, located in the Kyeongnam Province, was re-interpreted based on the hydrochemical and isotopic data published by Yun et al. (1998). The geothermal waters of the Bugok area is geochemically divided into three groups; Geothennal water I, II and III groups. Groups I and II are geochemically similar; high temperature (55.2-77.2$^{\circ}$C) and chemically belonging to Na-S04 types. However, pH and Eh values are a little different each other and Group II water is highly enriched in S04 compared to Group I water. Group III water, occurring from peripheral sites of the central part of the geothennal waters, shows temperature range of 29.3 to 47.0$^{\circ}$C and belongs to $Na-HCO_3-S0_4$ types. The deep environment and geochemical evolution of the Bugok geothennal waters, showing the diversity of geochemistry, can be interpreted as follows; I) Descending to great depth of meteoric waters that originated at high elevation and reacting with sediments and/or granites in depth. The $S0_4$ concentration of the waters has been increased by the dissolution of sulfate minerals in sediments. 2) During the continuous descending, the waters has met with the reduction environment, producing the $H_2S$ gas due to sulfate reduction. The waters has been heated up to 130$^{\circ}$C and the extent of water-rock reaction was increased. At this point, pH of waters are increased, S04 concentration decreased and calcite precipitated, therefore, the waters show the $Na-S0_4$ type. 3) Ascending of the geothennal waters along the flow path of fluids and mixing with less-deeply circulated waters. The $S0_4$ concentration is re-increased due to the oxidation of $H_2S$ gas and/or sulfide minerals in sediments. During continuous ascending, these geothennal waters are mixed with shallow groundwater.
For the reasonable use of low grade-shallow geothermal energy by Standing Column Well(SCW) system, the basic requirements are depth-wise increase of earth temperature like $2^{\circ}C$ per every 100m depth, sufficient amount of groundwater production being about 10 to 30% of the design flow rate of GSHP with good water quality and moderate temperature, and non-collapsing of borehole wall during reinjection of circulating water into the SCW. A closed loop type-vertical ground heat exchanger(GHEX) with $100{\sim}150m$ deep can supply geothermal energy of 2 to 3 RT but a SCW with $400{\sim}500m$ deep can provide $30{\sim}40RT$ being equivalent to 10 to 15 numbers of GHEX as well requires smaller space. Being considered as an alternative of vertical GHEX, many numbers of SCW have been widely constructed in whole country without any account for site specific hydrogeologic and geothermal characteristics. When those are designed and constructed under the base of insufficient knowledges of hydrgeothermal properties of the relevant specific site as our current situations, a bad reputation will be created and it will hamper a rational utilization of geothermal energy using SCW in the near future. This paper is prepared for providing a guideline of SCW design comportable to our hydrogeothermal system.
The purpose of this study is to characterize the hydrogeochemical characteristics of hot spring waters and to interpret the source of noble gases and the geochemical environment of the hot spring waters distributed along the eastern area of the Korean peninsula. For this purpose, We carried out the chemical, stable isotopic and noble gas isotopic analyses for eleven hot spring water and fourteen hot spring gas samples collected from six hot spring sites. The hot spring waters except the Osaek hot spring water show the pH range of 7.0 to 9.1. However, the Osaek $CO_2$-rich hot spring water shows a weak acid of pH 5.7. The temperature of hot spring waters in the study area ranges from $25.7^{\circ}C$ to $68.3^{\circ}C$. Electrical conductivity of hot spring waters varies widely from 202 to $7,130{\mu}S/cm$. High electrical conductivity (av., $3,890{\mu}S/sm$) by high Na and Cl contents of the Haeundae and the Dongrae hot spring waters indicates that the hot spring waters were mixed with seawater in the subsurface thermal system. The type of hot springs in the viewpoint of dissolved components can be grouped into three types: (1) alkaline Na-$HCO_3$ type including sulfur gas of the Osaek, Baekam, Dukgu and Chuksan hot springs, and (2) saline Na-Cl type of the Haeundae and Dongrae hot springs, and (3) weak acid $CO_2$-rich Na-$HCO_3$ type of Osaek hot spring. Tritium ratios of the Haeundae and the Dongrae hot springs indicate different residence time in their aquifers of older water of $0.0{\sim}0.3$ TU and younger water of $5.9{\sim}8.8$ TU. The ${\delta}^{18}O$ and ${\delta}D$ values of hot spring waters indicate that they originate from the meteoric water, and that the values also reflect a latitude effect according to their locations. $^3He/^4He$ ratios of the hot spring waters except Osaek $CO_2$-rich hot spring water range from $0.1{\times}10^{-6}$ to $1.1{\times}10^{-6}$ which are plotted above the mixing line between air and crustal components. It means that the He gas in hot spring waters was originated mainly from atmosphere and crust sources, and partly from mantle sources. The Osaek $CO_2$-rich hot spring water shows $3.3{\times}10^{-6}$ in $^3He/^4He$ ratio that is 2.4 times higher than those of atmosphere. It provides clearly a helium source from the deep mantle. $^{40}Ar/^{36}Ar$ ratios of hot spring water are in the range of an atmosphere source.
Kim, Hong-Gyun;Kim, Seung-Hyun;Ok, Young-Seok;Koo, Ho-Bon
The Journal of Engineering Geology
/
v.22
no.3
/
pp.331-341
/
2012
Granitoid rocks are generally high-quality rock from a geotechnical perspective, because they rarely contain systematic joints or fragmented fault zones. Although the rock type at the Sanhak site is granite, a collapsed slope has a deep soil layer and shows no residual structures such as discontinuities or faults; surface avalanches from this slope can be observed in several places. To study the stability of this slope, we investigated rainfall duration, variation in pore-water pressure, and the factor of safety considering three cases (current cross-section, initial planning cross-section, revised planning cross-section). With increasing duration of rainfall, the groundwater level rises, up to 20 m in height from ground surface. In the initial planning cross-section, safety was secure for rainfall of 2 days duration, but inadequate for rainfall of 4 days duration. In the revised planning cross-section, however, safety factors were secure for rainfall of 4 days duration. Therefore, to ensure permanent stability at the Sanhak site, a slope degree of 1:1.8 should be maintained during cutting.
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