• Korean Journal of Environmental Agriculture
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• v.25 no.3
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• pp.236-246
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• 2006

In this study, we give insight into questionable results that can be encountered in the conventional sequential extraction of heavy metals (Cd, Cu, and Zn) from soils. Objectives of this study were to determine the extraction variability of exchangeable (EXC)-metals as using six different EXC-extractants commonly accepted, and to investigate selectivity problems with carbonates bound (CAB)-metal fraction, a buffered acetate (1.0 M NaOAc; pH 5.0) extractable-metal fraction, leading to erratic results in especially non-calcareous soils. The contents of EXC-metals were markedly varied with the different extractability of various EXC-metal extractants used. The contents of EXC-Cd fraction were ranged from 2.0 to 74.3% of total Cd content in all of the metal spiked soils studied. The contents of EXC-Zn fraction extracted with the different EXC-extractants were varied with soil types, which were from 0.4 to 3.9% of total Zn in the calcareous soils, from 7.6 to 17.9% in the acidic soil, and from 13.6 to 56.8% in the peat soil. However, the contents of EXC-Cu fraction were relatively similar among the applications of different EXC-meal extractants, 0.2 to 2.1 % of total Cu, in all soils tested. Also, these varied amounts of EXC-metal fractions, especially Cd and Zn, seriously impacted the contents of subsequent metal fractions in the procedure. Furthermore, the CAB-Cd, -Cu, and -Zn fractions extracted by the buffered acetate solution were in critical problem. That is, the buffered acetate solution dissolved not only CAB-metals but also metals that bound or occupied to subsequent fractions, especially OXD-metal fraction, in both calcareous and non-calcareous soils. The erratic results of CAB-fraction also seriously impacted the amounts of subsequent metal fractions. Therefore, the conventional sequential extraction should be reconsidered theoretically and experimentally to quantify the target metal fractions or might be progressively discarded.

• ETRI Journal
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• v.32 no.5
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• pp.676-686
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• 2010

Mining sequential patterns is an important research issue in data mining and knowledge discovery with broad applications. However, the existing sequential pattern mining approaches consider only binary frequency values of items in sequences and equal importance/significance values of distinct items. Therefore, they are not applicable to actually represent many real-world scenarios. In this paper, we propose a novel framework for mining high-utility sequential patterns for more real-life applicable information extraction from sequence databases with non-binary frequency values of items in sequences and different importance/significance values for distinct items. Moreover, for mining high-utility sequential patterns, we propose two new algorithms: UtilityLevel is a high-utility sequential pattern mining with a level-wise candidate generation approach, and UtilitySpan is a high-utility sequential pattern mining with a pattern growth approach. Extensive performance analyses show that our algorithms are very efficient and scalable for mining high-utility sequential patterns.

• Journal of the Korean GEO-environmental Society
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• v.2 no.3
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• pp.17-35
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• 2001

In this study, we conducted a combined adsorption-sequential extraction analysis(CASA) to investigate temperature effects of single adsorption of lead, copper, zinc and cadmium on natural clays. As a result, it was found that in a single adsorption of lead and copper, about 50% of adsorption was occluded in carbonate phase, and in case of cadmium, about 80% of adsorption was occluded in exchangeable phase. At temperature below $25^{\circ}C$ about 60% of zinc was occluded in exchangeable phase but above $40^{\circ}C$ about 50% of zinc was occluded in carbonate phase. The effect of temperature on each occluded phase was largely observed in Fe-oxide, Mn-oxide and organic occluded phases. Besides, the adsorption of metals on natural clays was an endothermic reaction with the exception of exchangeable phase adsorption.

• Journal of Soil and Groundwater Environment
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• v.23 no.4
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• pp.48-59
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• 2018

Beryllium (Be), cobalt (Co), thallium (Tl) and vanadium (V) are candidates of 21 priority soil pollutants in Korea. The distribution of their concentration in soils from three contamination sources including industrial, roadside and mining areas was investigated. Concentrations of the metals were evaluated quantitatively using pollution indices and the fractionation of metals was conducted using modified SM&T (Standards Measurements and Testing programme) sequential extraction. Concentrations of the metals for all samples from industrial and roadside soils were within the range of natural background levels, while some of Be in soils from abandoned mines exceeded that the range. Enrichment Factor (EF) and Nemerow Integrated Pollution Index (NIPI) for Be, Co, Tl and V showed that there are effects or possibilities of anthropogenic activities. Pollution Load Index (PLI) analyses indicated all investigated sites needed further monitoring. The results of sequential extractions indicated mobile fractions (F1+F2) of Be, Tl and V were below 30% except some of Co in soil, which implies their low mobility to neighboring environment media. Variable tools like sequential extraction, comparison with background/actual concentration and pollution indices, as well as aqua regia extraction should be considered when evaluating Be, Co, Tl, V in soil.

• Journal of the Korean Geotechnical Society
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• v.16 no.4
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• pp.157-170
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• 2000

In this study, we conducted a combined adsorption-sequential extraction analysis(CASA) to investigate temperature effects of single and competitive adsorption of zinc and copper on natural clays. As a result, it was found out that in a single adsorption of zinc, the adsorption was mostly in the exchangeable phase, with increase n temperature. In a competitive adsorption of zinc, this trend was so strong that the exchangeable phase adsorption increase up to 80~90%. On the other hand, about 50% of copper was adsorbed in the carbonate occluded phase in single and competitive adsorptions. In the single adsorption the adsorption of carbonate occluded phase increased by 5% with the temperature increase and in the competitive adsorption the increase rate is about twice. The adsorption of zinc and copper on natural clays is an endothermic reaction with the exception of exchangeable phase adsorption.

• Economic and Environmental Geology
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• v.27 no.5
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• pp.469-477
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• 1994

Many researchers have investigated most representative sequential extraction method using various reagents for determining the chemical forms of metals in soils and sediments. In this paper, a newly modified method for sequential extraction scheme based on Tessier's method by Environmental Geochemistry Research, Centre for Environmental Technology, Imperial College, was introduced and examined. In comparison with Tessier's method, originally designed for sediment analysis by Atomic Absorption Spectrophotometry (AAS), the sequential extraction scheme has been developed for the multi-element analysis by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). The partitioning of particulate trace elements was classified into five fractions: (i) exchangeable, (ii) bound to carbonates or specially adsorbed, (iii) bound to Fe and Mn oxides, (iv) bound to organic matter and sulphides and (v) residuals. The experimental results of the pilot study for in-house reference material (HRM2) and certified international standard reference material (SRM2711) using the modified method showed not only reasonable precision and accuracy but also acceptable overall recovery rates. In addition, mine dump soils sampled in the Dalsung Cu-W mine, Korea were prepared and sequentially extracted using the method. Most of Cu was bound to organic matter/sulphides and residual fractions. The dominant fraction of soil Pb and Zn in the study area was found in the residuals. The fraction of Cd showed a wide variation between samples and could be found bound to the carbonates or specially adsorbed, oxides, organic fraction and residuals. The recovery rates of Cd, however, were poor due to relatively low Cd concentrations in soils. The heavy metals in these mine dumps appear to be in the more inert forms and should not be readily bioavailable. The soils, however, had very low pH values (average 4.1) and had sandy textures; consequently, rapid infiltration of rainfall may increase leaching of Zn and Cd which were found to be around 5 to 10% of the exchangeable fraction. As a result of the investigation of this study, it has been strongly recommended that these mine waste materials should still be considered a significant contaminant source and will need environmental remediation to prevent pollutants from being released into the environment.

• Journal of Soil and Groundwater Environment
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• v.16 no.1
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• pp.42-50
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• 2011

Potential risk of heavy metals to various receptors including humans depends on the bioavailability of the heavy metals in soil. In this study, the heavy metal extraction methods using 0.1N HCl and aqua regia were compared with the Tessier's sequential extraction method to assess whether these two methods can be used to determine the plant-available heavy metal concentrations. The contamination characteristics of copper (Cu), cadmium (Cd), lead (Pb), and arsenic (As) found in soils collected from 75 sites around the closed Janghang smelter were analyzed by extracting heavy metals using 0.1 N HCl, aqua regia, and the Tessier's sequential extraction method. The portion of metals bioavailable to plants is considered as the sum of the fraction 1 (exchangeable) and the fraction 2 (carbonates binding) of the Tessier's 5-step sequential extraction method, which were determined to be 3.1 ${\pm}$ 3.82, 0.6 ${\pm}$ 0.15, 20.6 ${\pm}$ 18.78, and 7.0 ${\pm}$ 6.48 mg/kg for Cu, Cd, Pb, and As, respectively, in this study. When the extraction using aqua regia and the Tessier's extraction method were compared, the extracted Cu and Pb concentrations did not show significant differences, whereas the extracted Cd and As concentrations showed significant differences. These results indicate that the portion of Cd and As in the fraction 5 of the Tessier's sequential extraction can not be extracted using aqua regia. Using aqua regia, which is the official test method, higher concentrations of Cu, Cd, Pb and As were extracted than the sum of the fraction 1 and 2. The results show that only 9, 40, 39 and 10% of Cu, Cd, Pb and As using aqua regia can be uptaken by plants (i.e., plant-available). Using 0.1N HCl, the portion of Cd equivalent to about 66% the fraction 1 could be extracted, while, with Pb, the portion of the fraction 1 and about 90% of the fraction 2 could be extracted. With As, the portion equivalent to the fraction 1, 2 and 79% of the fraction 3 was extracted, while with Cu, the portion equivalent to the fraction 1, 2, 3 and 20% of the fraction 4 was extracted using 0.1N HCl.

• Journal of Soil and Groundwater Environment
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• v.23 no.2
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• pp.15-22
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• 2018

Aqua regia extraction for the quantification of heavy metals and As in contaminated soils was investigated as one of preliminary steps for on-site monitoring using sensor technology. Soil samples were taken from closed railway depot, closed mines, and closed refinery and various extraction conditions including $30^{\circ}C/15min$, $30^{\circ}C/30min$, $30^{\circ}C/60min$, $30^{\circ}C/120min$, $80^{\circ}C/15min$, $80^{\circ}C/30min$, $80^{\circ}C/60min$, $80^{\circ}C/120min$ were tested. The optimal extraction condition was determined as $80^{\circ}C/60min$ because the extraction efficiencies of Zn were relatively low and did not reach the targeted level (80-100% of original concentrations) for $30^{\circ}C$ conditions. It was found that the fractionation of heavy metals and As using the sequential extraction method was useful to understand the degree of metal extraction. In order to enhance the extraction efficiency within short extraction time, ultrasound technology using a 20 kHz horn-type sonicator was additionally used for $30^{\circ}C/15min$. It was revealed that ultrasound could significantly enhance the extraction efficiency and pulsed irradiation showed higher efficiency than continuous irradiation due to the less formation of bubble clouds. However high temperature condition ($80^{\circ}C$) was required to achieve high extraction efficiency for Zn in spite of the use of ultrasound.

• Journal of Environmental Impact Assessment
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• v.9 no.4
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• pp.301-314
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• 2000

Marine surface sediments in the vicinity of Samcheonpo coal-fired power plant were analyzed by a total analysis($HF+HNO_3+HClO_4$) and sequential extraction procedure for heavy metals in order to investigate the total concentrations and geochemical phases of heavy metals. The result showed that the concentrations of Cr, Cu, Fe and Zn were within ranges typical for coastal areas, which reflected the mineralogical composition of the sediments in the studied area. However, the distributions of Cd, Co, Mn, Ni and Pb were rather different from the former, indicating that these heavy metals had a different origin, or that they were affected by a different geochemical mechanism. Chemical partitioning of heavy metals using sequential extraction procedure revealed that Cu, Fe, Pb, Zn were significantly bound to the residual phases of the sediments, whereas carbonate phases contained considerable amounts of Mn. The significant association of Pb with the exchangeable fraction also indicated that Pb was more mobile and bioavailable than Cu, Fe, Mn, Zn.

• Journal of the Korean Geotechnical Society
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• v.16 no.2
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• pp.91-102
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• 2000

자연점토지반에서의 중금속 흡착시 온도변화에 따른 영향은 지금까지 2차적인 것으로 간주되었다. 그러나 최근 몇몇 연구자들에 의하면 온도변화가 중금속 흡착 거동에 큰 영향을 미친다고 보고하였다. 따라서 본 연구에서는 자연점토 지반에 대한 중금속 아연(Zn) 흡착시 온도변화에 따른 흙의 각 구성성분별 흡착거동을 살펴보기 위해 혼합 흡착-연속추출법(combined absorption-sequential extraction analysis, CASA)을 사용하였다. 실험결과 중금속 아연의 농도가 저농도(50mg/L 미만)일 경우 자연지반에서의 분배양상은 주로 탄산염 형태로 존재하고, 또한 온도의 증가에 따라 탄산염 형태의 흡착량이 증가하는 것을 알 수 있다. 하지만 고농도(50mg/L 이상)의 경우 분배양상은 주로 이온교환형태로 존재한다는 것을 알 수 있다. 그러나 고농도에서의 이러한 분배형태는 온도의 증가에 따라 탄산염형태의 흡착량이 약 20%정도 증가하는 결과를 얻었다. 결론적으로 중금속 아연의 자연점토지반의 각 구성성분 별 흡착거동은 이온교환 형태를 제외하고 온도증가에 따라 증가하는 흡열반응(ΔH0>0)인 것으로 나타났고, 또한 고농도에서의 분배형태는 이온교환 형태에서 탄산염 형태로 변화되는 것을 알 수 있다. 그리고 이온교환 형태의 경우 온도변화에 따라 독립적인 거동을 보였다.