• The Journal of Engineering Geology
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• v.21 no.2
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• pp.163-178
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• 2011

A test borehole was drilled in the Cheongwon area to investigate the relationship between geochemical environment and the natural occurrence of radioactive materials (uranium and Rn-222) in borehole groundwater. The borehole encountered mainly biotite schist and biotite granite, with minor porphyritic granite and basic dykes. Six groundwater samples were collected at different depths in the borehole using the double-packed system. The groundwater pH ranges from 5.66 to 8.34, and the chemical type of the groundwater is Ca-$HCO_3$. The contents of uranium and Rn-222 in the groundwater are 0.03-683 ppb and 1,290-7,600 pCi/L, respectively. The contents of uranium and thorium in the rocks within the borehole are 0.51-23.4 ppm and 0.89-62.6 ppm, respectively. Microscope observations of the rock core and analyses by electron probe microanalyzer (EPMA) show that most of the radioactive elements occur in the biotite schist, within accessory minerals such as monazite and limenite in biotite, and in feldspar and quartz. The high uranium content of groundwater at depths of -50 to -70 m is due to groundwater chemistry (weakly alkaline pH, an oxidizing environment, and high concentrations of bicarbonate). The origin of Rn-222 could be determined by analyzing noble gas isotopes (e.g., $^3He/^4He$ and $^4He/^{20}Ne$).

• The Journal of Engineering Geology
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• v.8 no.3
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• pp.247-259
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• 1998

Groundwater quality of the natural mineral water was investigated in hydrochemical aspects in order to ensure that mineral water meets stringent health standards. There exist 20 mineral water plants in the Daebo granite and 4 mineral water plants in the Bulguksa granite, respectively. Both granite areas show some differences in water chemistry. The pH, EC, hardness, total ionic contents in groundwater of the Daebo granite area are higher relative to those of the Bulguksa granite area. The content of major cations is in the order of Ca>Na>Mg>K, while that of major anions shows the order of $HCO_3>SO_4$>Cl>F. The fact that the $Ca-Na-HCO_3$ type is most predominant among water types may reflect that the dissolution of plagioclase that is most abundant in granitic rocks plays a most important role in groundwater chemistry. Representative correlation coefficients between chemical species are variable depending on geology. In the Daebo granite area, $Ca-HCO_3(0.84),{\;}Mg-HCO_3(0.81),{\;}SiO_2-Cl(0.74),{\;}Na-HCO_3(0.70)$ show relatively good correlationships. In the Bulguksa granite area, fairly good correlationships are found among some components such as K-Mg(0.93), $K-HCO_3(0.92)$, Mg-Cl(0.92), $Cl-HCO_3(0.91)$, and K-F(0.90). According to saturation index, most chemical species are undersaturated with respect to major minerals, except for some silica phases. Groundwater is slightly undersaturated with respect to calcite, whereas it is still greatly undersaturated with respect to dolomite, gypsum and fluorite. Based on the phase equilibrium it is clear that groundwater is mostly in equilibrium with kaolinite and becomes undersaturated with respect to feldspars, evolved from the stability area of gibbsite during water-rock interaction. While the activity of silica increases, there is no remarkable increase in the acivities of alkali ions and pH, which indicates that some amounts of silicic acid dissolved from silica phases as well as feldspars were provided to groundwater. It is concluded that chemical evolution of groundwater in granite aquifers may continue to proceed with increasing pH.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.420-424
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• 2005

K시 강변여과수 개발 지역에서 적정 채수량 산정 및 지표수 연계 특성을 파악하기 위한 적절한 현장 시험 세부계획 수립과 그 근거를 마련하였다. 일반적으로 단계양수시험을 통하여 적정 채수량 산정 후, 산정된 적정 채수량으로 장기양수 시험을 통하여 주변 수리권에 미치는 지하수위 변화와 강변여과수의 수질변화를 관찰하여 지표수와 연계한 변동특성을 파악하는 일련의 과정을 생각할 수 있다. 그러나 K시 강변여과수 개발 지역과 같은 연약 지반에서는 단계 양수시험시의 높은 양수량에 인한 지반 침하의 우려로 인해 이에 대한 공정의 변화가 불가피하였다. 따라서 현장 시험 공정 순서를 바꾸어서 장기 양수 시험 후 단계양수시험을 수행하는 새로운 대안을 모색하였고 이를 뒷받침 해주는 근거를 제시하고자 한다. 뿐만 아니라 단계양수시험의 단계별 적절한 양수시간을 합리적, 효율적으로 결정하여 경제적이면서 가급적 빠른 시간 내에 단계양수시험을 완료 가능하게 만들고, 가능한 한 더 오랜 기간동안 장기 양수 시험을 가능하게 함으로써 제한된 시간내에 많은 수리지질학 및 화학적인 정보를 얻을 수 있도록 하였다.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.09a
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• pp.215-218
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• 2002

The purposes of this research are to identify the source and the extent of contamination of nitrate in groundwater in a typical agricultural area. The study area has many livestock raising facilities, rice paddies and grape farms. In order to identify the hydrogeological character, we sampled groundwater and surface water in 27 locations and performed chemical analyses. Nitrate-nitrogen is the major contaminant in this area. Approximately 32 ~ 42% of groundwater samples are over the drinking water limit(10 mg/L) and 77% estimated to be entered from artificial sources. The nitrogen isotope analysis indicates animal waste being the major source of nitrate in water samples. Not only presently operating livestock facilities but also abandoned ones influence groundwater quality for a long time.

• The Journal of Engineering Geology
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• v.12 no.4
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• pp.379-394
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• 2002

This study was initiated to identify groundwater quality and contamination at present in the 'A' section of Seoul Metropolitan Subway. Groundwater samples were collected at 21 boreholes along the 'A' section and appeared to show mainly $Ca-HCO_3$ type. In 20 samples, concentration of $SO_4$, Cd, Pb, Fe, Mn, Al, F and $NO_3-N$ were higher than those of Korean drinking water quality standards. From chemical data and saturation Indices, contaminant sources of individual chemical elements were inferred to be buried wastes and surface sediments over the study area. The result of factor analysis suggested that the pollution factor should account for about 47% of data variation.

• Applied Chemistry for Engineering
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• v.30 no.5
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• pp.627-632
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• 2019

In this study, Laminaria japonica was used as a substrate for a mixed aerobic microbial consortium. Laminaria japonica is well-known as a representative brown algal biomass possessing advantages of cheap cost, and high productivity and carbohydrate content. A biological saccharification system was established by inoculating and enriching the mixed aerobic microbial consortium. Production of the soluble carbohydrate and reducing sugar at different hydraulic retention times (HRT) was observed. The efficiency of saccharification increased according to the decrease of HRT. The maximum saccharification yield in a continuous biological pretreatment process was 17.96 and 4.30 g/L/day for the soluble carbohydrate and reducing sugar, respectively at the HRT of 1 day. In contrast, the staccharification yield decreased drastically at the HRT of 0.5 day. Experimental results indicate that Laminaria japonica is a promising material for the production of useful products, in particular for the saccharification through a biorefinery process. It can thus be concluded that a continuous biological pretreatment process using a mixed cultivation system can be successfully employed for the biorefinery technology.

• The Journal of Engineering Geology
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• v.22 no.1
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• pp.95-111
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• 2012

This study investigated the relationship between the geochemical environment and the occurrence of natural radioactive materials (uranium and Rn-222) in borehole groundwater at an Icheon site. The drill core recovered from the study site consists mainly of biotite granite with basic dykes. The groundwater samples were collected at four different depths in the borehole using the double-packed system. The pH range of the groundwater was 6.5~8.6, and the chemical type was Ca-$HCO_3$. The ranges of uranium and Rn-222 concentrations in the groundwater were 8.81~1,101 ppb and 5,990~11,970 pCi/L, respectively, and concentrations varied greatly with depth and collection time. The ranges of uranium and thorium contents in drill core were 0.53~18.3 ppm and 6.66~17.5 ppm, respectively. Microscope observations and electron microprobe analyses revealed the presence of U and Th as substituted elements for major composition of monazite, ilmenite, and apatite within K-feldspar and biotite. Although the concentration of uranium and thorium in the drill core was not high, the groundwater contained a high level of natural radioactive materials. This finding indicates that physical factors, such as the degree of fracturing of an aquifer and the groundwater flow rate, have a greater influence on the dissolution of radioactive materials than does the geochemical condition of the groundwater and rock. The origin of Rn-222 can be determined indirectly, using an interrelationship diagram of noble gas isotopes ($^3He/^4He$ and $^4He/^{20}Ne$).

• Economic and Environmental Geology
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• v.54 no.6
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• pp.699-707
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• 2021

Hwajinpo Lagoon, located on the eastern coast of Korea, is a unique environment where freshwater and saltwater are mixed. Systematic management of the lagoon is required because it is a biodiversity-rich and area of high conservation value. The existing environment of the lagoon was evaluated by identifying the distribution of the groundwater level and groundwater flow characteristics. In addition, hydrogeochemical fluctuations were analyzed to determine the effect of seawater intrusion into the aquifer. The results demonstrate that the freshwater-saltwater interface is distributed throughout the aquifer and rises when water of the lagoon evaporates due to prolonged periods of low rainfall and high temperature, thereby increasing the possibility of seawater inflow through groundwater. As for the ionic delta properties (difference between the measured and theoretical concentration of mixed waters), it was estimated that the cation-exchange and precipitation reactions occurred in the aquifer due to seawater intrusion. The ratio of seawater mixed at each point was calculated, using oxygen isotopes and chloride as tracers, resulting in an average of 0.3 and a maximum of 0.87. The overall seawater mixing ratio appears to be distributed according to the distance from the coast. However, some of the results were deviated from the theoretical expectations and reflected the characteristics of the nearby aquifers. Further research on seasonal changes and simulation of seawater intrusion mechanisms is required for specific analysis.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.196-196
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• 2020

토양은 육상생태계에 있어 가장 많은 탄소를 저장하고 있으며, 대기 중 CO₂를 토양탄소로 전환하여 쉽게 방출되지 않고 토양 내에 저장하는 역할을 한다. 이렇듯 토양 유기탄소 배출관리는 기후변화에 있어 중요한 문제로 대두되고 있다. 하지만 토지이용의 변화와 무분별한 관리로 인하여 토양내에 저장되어 있는 토양 탄소배출이 지속적으로 증가 하고 있다. 따라서 토양탄소 배출로 인한 경제적 피해를 수치적으로 표현하는 가치평가가 필요하다. 현재 토양에 저장된 토양유기탄소 함량을 토양통별로 토양정보시스템에서 제공하고 있지만 국내 토양 토양탄소 저장량의 산정에 관한 연구는 미비한 실정이다. 따라서 본 연구에서는 토양 특성을 이용하여 토양 유기탄소 저장량을 산정하고, 산정된 토양 유기탄소 저장량과 정밀토양도를 이용하여 남한의 토양 유기탄소 가치평가를 실시하였다. 토양의 특성은 물리적 특성인 모래(Sand), 이토(Silt), 점토(Clay), 자갈(Gravel)함량과 화학적 특성인 유기물함량(Organic Matter)를 사용하였다. 토양 유기탄소저장량 산정의 검증을 위하여 전라남도 진도군의 토양유기탄소 저장량을 산정한 결과 486,696t으로, 선행연구와 유사한 결과를 나타내었다. 이러한 검증 결과를 바탕으로 남한의 토양 유기탄소 저장량을 산정한 결과 305.54Mt의 유기탄소가 저장된 것으로 나타났으며, 단위 면적당 유기탄소 저장량의 경우 3.11kg/㎡으로 나타났다. 또한 2019년 상반기 기준 평균 탄소거래권 가격(27,500원/톤)을 이용하여 우리나라 국토의 토양탄소 저장량 가치평가를 실시한 결과, 약 8조 4천억원의 경제적 가치가 있는 것으로 나타났다. 본 연구는 토양의 물리적·화학적 특성을 이용하여 토양의 유기탄소 저장량을 산정하였으며, 토양에 저장되어 있는 유기탄소의 가치평가를 수행하였다. 본 연구결과는 농업, 수문, 기후변화 등 다양한 분야에서 필요로 하는 기초자료로 활용될 수 있을 것으로 판단된다.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.6
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• pp.603-612
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• 2006

The study with laboratory sandbox model has been carried out to address potential use of reclaimed water, as a way for artificially recharging the coastal aquifer, to effectively prevent from seawater intrusion. To do this, we assessed hydraulic and geochemical properties depending upon various extraction and recharging conditions. While solely being recharged, the intrusion could be significantly retarded than those of recharge and extraction implied together. At 0.5 to 2 for the ratio of the extraction over the recharge rate, the fresh water was exploited from the tank, where the void regime was simultaneously saturated with the recharged water. In the meantime, the saline water zone was diluted and back-tracked by the recharged water due to forming a hydraulic geochemical barrier around the injection well. However, if the ratio was being increased to greater than 4, saltwater more deeply intruded to the freshwater zone because the artificial recharge was not sufficiently supplied to timely back-fill the void space. When the aquifer water was intermittently extracted at the ratio of $0.5{\sim}2$ over the recharge rate, the value of S.M.I. decreased, but increasing it to more than 4 unlikely escalated the value of S.M.I as much as $3{\sim}47%$ indicating that the salt water intruded. It finally revealed that the proper ratio of extraction/recharge or intermittent extraction would efficiently retracted seawater intrusion while the freshwater sources could be conservatively utilized.