• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2004년도 총회 및 춘계학술발표회
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• pp.97-99
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• 2004

To understand the geochemical processes controlling the distribution of nitrate and other agricultural constituents in an alluvial aquifer, hydrogeological and hydro geochemical studies were carried out in an agricultural area within Cheonan. In this selected field, nitrate concentrations were very wide in range but was locally attenuated significantly down to very low levels (<1.0 mg/L). Abrupt removal of nitrate coincided with the pattern of redox change and thus indicated that geochemical processes occurring during and after recharge events control the behavior and distribution of nitrate and other redox-sensitive chemical species.

• Ocean and Polar Research
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• 제44권2호
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• pp.139-145
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• 2022

Manganese nodules were recovered within the deep subseafloor sediments (118.22 mbsf) at Site U1371 during International Ocean Discovery Program (IODP) expedition 329 from the South Pacific Gyre (SPG). Because most manganese nodules exist on the seabed surface, nodules present in deep sediments are uncommon. Therefore, the growth origin of manganese nodules was identified through mineralogical and geochemical analyses. The manganese nodule was divided into the concentric layer outside the manganese region and the inner part of the phosphatized region consisting of manganese oxide minerals and carbonate fluorapatite (CFA) minerals, respectively. The two-dimensional element distribution analysis of Mn, Co, Ni, Sr and Cu, Zn with low Mn/Fe ratio confirmed that manganese nodules were formed predominantly by a hydrogenetic process and a biogenic process in certain manganese layers. As a result, the manganese nodule was continuously precipitated in SPG environments of oligotrophic open paleoocean conditions and rapidly buried with siliceous ooze sediments when the SPG changed to a eutrophic environment. It has been confirmed that manganese nodules found within deep subseafloor sediments could be used as a new proxy for the reconstruction of paleooceanographic conditions.

• 대한자원환경지질학회:학술대회논문집
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• 대한자원환경지질학회 2002년도 제18차 공동학술강연회 자연저감고 지질학 (대한 자원 환경지질학회)
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• pp.81-100
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• 2002

While most of regulatory communities in abroad recognize ' 'natural attenuation " to include degradation, dispersion, dilution, sorption (including precipitation and transformation), and volatilization as governing Processes, regulators prefer "degradation" because this mechanism destroys the contaminant of concern. Unfortunately, true degradation only applies to organic contaminants and short- lived radionuclides, and leaves most metals and long-lived radionuclides. The natural attenuation Processes may reduce the potential risk Posed by site contaminants in three ways: (i)contaminants could be converted to a less toxic form througy destructive processes such as biodegradation or abiotic transformations; (ii) potential exposure levels may be reduced by lowering concentrations (dilution and dispersion); and (iii) contaminant mobility and bioavailability may be reduced by sorption to geomedia. In this review, authors will focus will focul on "sorption" among the natural attenuation processes of hazardous inorganic contaminants including radionuclides. Note though that sorption and transformation processes of inorganic contaminants in the natural setting could be influenced by biotic activities but our discussion would limit only to geochemical reactions involved in the natural attenuation. All of the geochemical reactions have been studied in-depth by numerous researchers for many years to understand "retardation" process of contaminants in the geomedia. The most common approach for estimating retardation is the determination of distrubution coefficiendts ($K_{d}$) of contaminants using parametric or mechanistic models. As typocally used in fate and contaminant transport calculations such as predictive models of the natural attenuation, the $K_{d}$ is defined as the ratio of the contaminant concentration in the surrounding aqueous solution when the system is at equilibrium. Unfortunately, generic or default $K_{d}$ values can result in significant error when used to predict contaminant migration rate and to select a site remediation alternative. Thus, to input the best $K_{d}$ value in the contaminant transport model, it is essential that important geochemical processes affecting the transport should be identified and understood. Precipitation/dissolution and adsorption/desorption are considered the most important geochemical processes affecting the interaction of inorganic and radionuclide contaminants with geomedia at the near and far field, respectively. Most of contaminants to be discussed in this presentation are relatively immobile, i.e., have very high $K_{d}$ values under natural geochemical environments. Unfortunately, the obvious containment in a source area may not be good enough to qualify as monitored natural attenuation site unless owner demonstrate the efficacy if institutional controls that were put in place to protect potential receptors. In this view, natural attenuation as a remedial alternative for some of sites contaminated by hazardous-inorganic components is regulatory and public acceptance issues rather than scientific issue.

• Nuclear Engineering and Technology
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• 제25권1호
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• pp.154-165
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• 1993

연속시간 마코프프로세스를 이용한 한 통계적 방법에 의한 일차원 지하 핵종이동 모델이 제시되었다. 지하매질은 보편적으로 지하수속도, 분산계수 또는 지연계수 등 물리화학적 변수 등의 비균질성을 보여 일반적인 결정론적 이류분산모델로는 잘 기술되지 않는다. 통계적 모델에서의 최종결과는 시간에 따른 함수로서의 기대값과 그 기대값의 분산도를 보여주는 분산치다. 매질이 균질하다고 생각될 정도로 나뉘어진 구획에 대한 핵종의 농도 분포를 구하여 결정론적인 해석해에 의한 농도분포와 비교하여 비균질 매질, 또는 현저하게 구분되는 다층매질의 경우에 대해서 유용 할 것이라는 결론을 얻었다. 매질을 나눈 구획수가 수치적 분산에 민감한 것으로 나타났지만 해석적 모델에 의해 분산계수가 보정될 수 있었다.

• 한국해양학회지:바다
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• 제9권4호
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• pp.196-203
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• 2004

한강 기수역에서 일어나는 지화학적 변화과정을 파악하기 위하여 2000년 6월과 2001년 2월 두 차례에 걸쳐 용존 무기영양염류,용존 유기 탄소,추출된 용존 유기물의 형광 특성, 용존 우라늄의 분포특성에 대해서 연구하였다. 용존 무기 영양염류는 염분이 증가함에 따라 감소하였는데,특히 질소계 영양염류의 경우 기수역에서 뚜렷한 질산화 과정(nitrification process)을 보였다. 인산-인 또한 질소계 영양염류와 같이 기수역에서 비보존적 분포특성을 보였다 용존 유기탄소와 형광 유기물은 염분이 증가함에 따라 감소하는 모습을 보였는데, 특히 5 psu이하의 저염분대에서 급격히 감소하는 양상을 나타내었다. 이러한 현상은 육상 기원의 지구거대 유기물질이 이온강도가 증가하는 기수역에서 응집, 침전하여 제거되기 때문으로 생각된다. 한편 용존 우라늄은 대부분 강을 통하여 해양으로 유입되는데, 염분이 증가함에 따라 같이 증가하는 양의 상관관계를 보였다. 용존 우라늄은 기수역에서 제거되는 비보존적인 분포 특성을 보였는데. 이는 용존 우라늄의 일부가 유기물질과 착화합물의 형태로 제거되기 때문으로 생각된다. 염분과 용존 우라늄의 분포 상관관계로부터 추정된 한강 기수역에서 용존 우라늄 제거량은 약 7.1 ton/year으로 Savannah salt marsh에서의 제거량과 비교해볼 때 약 51.4%에 해당하였다.

• 한국산림과학회지
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• 제99권5호
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• pp.755-761
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• 2010

This study analyzed water quality data from a coniferous forest catchment in order to quantify the contributions of runoff components to stormflow, and to understand the effects of antecedent moisture conditions within catchment on the contributions of runoff components. Hydrograph separation by the twocomponent mixing model analysis was used to partition stormflow discharge into pre-event and event components for total 10 events in 2005 and 2008. To simplify the analysis, this study used single geochemical tracer with Na+. The result shows that the average contributions of event water and pre-event water were 34.8% and 65.2% of total stormflow of all 10 events, respectively. The event water contributions for each event varied from 18.8% to 47.9%. As the results of correlation analysis between event water contributions versus some storm event characteristics, 10 day antecedent rainfall and 1 day antecedent streamflow are significantly correlated with event water contributions. These results can provide insight which will contribute to understand the importance of antecedent moisture conditions in the generation of event water, and be used basic information to stormflow generation process in forest catchment.

• Environmental Engineering Research
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• 제24권2호
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• pp.279-288
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• 2019

To obtain insightful knowledge of geochemical process controlling fluoride enrichment in groundwater of the villages near Shilabati river bank, West Bengal, India, multivariate statistical techniques were applied to a subgroup of the dataset generated from major ion analysis of groundwater samples. Water quality analysis of major ion chemistry revealed elevated levels of fluoride concentration in groundwater. Factor analysis (FA) of fifteen hydrochemical parameters demonstrated that fluoride occurrence was due to the weathering and dissolution of fluoride-bearing minerals in the aquifer. A strong positive loading (> 0.75) of fluoride with pH and bicarbonate for FA indicates an alkaline dominated environment responsible for leaching of fluoride from the source material. Mineralogical analysis of soli sediment exhibits the presence of fluoride-bearing minerals in underground geology. Hierarchical cluster analysis (HCA) was carried out to isolate the sampling sites according to groundwater quality. With HCA the sampling sites were isolated into three clusters. The occurrence of abundant fluoride in the higher elevated area of the observed three different clusters revealed that there was more contact opportunity of recharging water with the minerals present in the aquifer during infiltration through the vadose zone.

• 방사성폐기물학회지
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• 제19권1호
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• pp.113-121
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• 2021

A safety assessment of radioactive waste repositories is a mandatory requirement process because there are possible radiological hazards owing to radionuclide migration from radioactive waste to the biosphere. For a reliable safety assessment, it is important to establish a parameter database that reflects the site-specific characteristics of the disposal facility and repository site. From this perspective, solubility, a major geochemical parameter, has been chosen as an important parameter for modeling the migration behavior of radionuclides. The solubilities were derived for Am, Ni, Tc, and U, which were major radionuclides in this study, and on-site groundwater data reflecting the operational conditions of the Gyeongju low and intermediate level radioactive waste (LILW) repository were applied to reflect the site-specific characteristics. The radiation dose was derived by applying the solubility and radionuclide inventory data to the RESRAD-OFFSITE code, and sensitivity analysis of the dose according to the solubility variation was performed. As a result, owing to the low amount of radionuclide inventory, the dose variation was insignificant. The derived solubility can be used as the main input data for the safety assessment of the Gyeongju LILW repository in the future.

• 방사성폐기물학회지
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• 제20권4호
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• pp.399-410
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• 2022

The solubility and species distribution of radionuclides in groundwater are essential data for the safety assessment of deep underground spent nuclear fuel (SNF) disposal systems. Americium is a major radionuclide responsible for the long-term radiotoxicity of SNF. In this study, the solubility of americium compounds was evaluated in synthetic groundwater (SynDB3), simulating groundwater from the DB3 site of the KAERI Underground Research Tunnel. Geochemical modeling was performed using the ThermoChimie_11a thermochemical database. Concentration of dissolved Am(III) in Syn-DB3 in the pH range of 6.4-10.5 was experimentally measured under over-saturation conditions by liquid scintillation counting over 70 d. The absorption spectra recorded for the same period suggest that Am(III) colloidal particles formed initially followed by rapid precipitation within 2 d. In the pH range of 7.5-10.5, the concentration of dissolved Am(III) converged to approximately 2×10^-7 M over 70 d, which is comparable to that of the amorphous AmCO₃OH(am) according to the modeling results. As the samples were aged for 70 d, a slow equilibrium process occurred between the solid and solution phases. There was no indication of transformation of the amorphous phase into the crystalline phase during the observation period.

• 분석과학
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• 제19권5호
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• pp.400-406
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• 2006

탄성되튐검출(Elastic Recoil Detection)법에 의한 박막시료의 수소 정량은 빔전류 측정의 신뢰성을 전제로 유기물 필름을 정량 비교체로 사용하여 이루어진다. 그러나 탄성되튐검출법에서 일반적으로 사용되는 편향각(tilt angle)인 $75^{\circ}$에서는 시편에 조사되는 일차 이온빔의 조사량을 정확하게 측정하기 어렵다. 시편의 편향각을 바꿔가며 탄성산란 신호를 비교하면 편향각이 커질수록 단위 조사량 당 산란신호는 감소하며 또한 시편의 표면 물질에 따라 이온빔전류 적산의 효율이 달라진다. 이러한 빔전류 적산과정의 오류를 제거하여 정량의 신뢰성을 제고하는 방법으로 되튐스펙트럼과 동시에 측정한 산란스펙트럼을 이용하여 빔 조사량을 결정하였다. 산란스펙트럼에 의한 조사량 결정법은 수 10%에 이르는 전류적산과정의 오차요인을 근본적으로 제거하여 되튐반응에 의한 수소정량의 신뢰성을 향상시켰다. 수소정량의 비교체로 사용해 왔던 폴리이미드 필름과 수소이온주입 시료, 그리고 카본웨이퍼를 대상으로 시험분석하고 기존의 전류적산에 의한 직접정량법과 비교하였다.