• Journal of Soil and Groundwater Environment
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• v.14 no.2
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• pp.17-25
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• 2009

The applicability of soil washing/flushing to treat a contaminated soil with cadmium (Cd) and copper (Cu) using a mixture of organic/inorganic extractant was evaluated in laboratory-scale batch and column tests. Citric acid was the effective extractant to remove Cd and Cu from the soil among various organic acids except EDTA. Carbonic acid was chosen as inorganic extractant which was not only low toxicity to environment, but also increasing soil permeability. Moreover, the optimum ratio of organic and inorganic extractant to remove Cd and Cu was 10 : 1, and this ratio of organic and inorganic extractant achieved removal efficiencies of Cd (46%) and Cu (39%), respectively. The increasing flow rate of extractant could explain the phenomena of soil packing when carbonic acid was used with organic extractant (i.e. EDTA and citric acid). Therefore, a mixture of organic extractant with inorganic extractant, especially carbonic acid, could resolve a problem of soil packing when this extractant was applied to a field application to remove Cd and Cu using in-situ soil flushing process.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.04a
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• pp.44-48
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• 2002

Washing technique using solubilization and surfactant as a extractant was studied by removing contaminants from the cohesive soil contaminated with heavy metal. For this purpose, the laboratory desorption batch tests were peformed in the kaolinite contaminated with lead by using acetic acid as a solubilization and SDS as a anionic surfactant. In desorption batch tests, the effects of extractant concentration and mixing ratio were investigated and also the coupling effects of acetic acid added with surfactant were considered. Test results show that the removal efficiency of acetic acid as a extractant in the kaolinite contaminated with lead increased with increasing the concentration of acetic acid and the acetic acid was found to be more effective when adding CMC 2 or 3 of surfactant. Additionally, regardless of the initial concentration, the efficiency of lead removal from the contaminated soil increased with increasing shaking ratio.

• Journal of Biosystems Engineering
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• v.31 no.6 s.119
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• pp.463-473
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• 2006

Automated sensing of soil macronutrients would allow more efficient mapping of soil nutrient spatial variability for variable-rate nutrient management. The capabilities of ion-selective electrodes for sensing macronutrients in soil extracts can be affected by the presence of other ions in the soil itself as well as by high concentrations of ions in soil extractants. Adoption of automated, on-the-go sensing of soil nutrients would be enhanced if a single extracting solution could be used for the concurrent extraction of multiple soil macronutrients. This paper reports on the ability of the Kelowna extractant to extract macronutrients (N, P, and K) from US Corn Belt soils and whether previously developed PVC-based nitrate and potassium ion-selective electrodes could determine the nitrate and potassium concentrations in soil extracts obtained using the Kelowna extractant. The extraction efficiencies of nitrate-N and phosphorus obtained with the Kelowna solution for seven US Corn Belt soils were comparable to those obtained with IM KCI and Mehlich III solutions when measured with automated ion and ICP analyzers, respectively. However, the potassium levels extracted with the Kelowna extractant were, on average, 42% less than those obtained with the Mehlich III solution. Nevertheless, it was expected that Kelowna could extract proportional amounts of potassium ion due to a strong linear relationship ($r^2$ = 0.96). Use of the PVC-based nitrate and potassium ion-selective electrodes proved to be feasible in measuring nitrate-N and potassium ions in Kelowna - soil extracts with almost 1 : 1 relationships and high coefficients of determination ($r^2$ > 0.9) between the levels of nitrate-N and potassium obtained with the ion-selective electrodes and standard analytical instruments.

• Economic and Environmental Geology
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• v.38 no.6 s.175
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• pp.657-662
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• 2005

Extractions fro fertilizer and soil samples were performed to yield the operationally defined fractions 'soluble' chromate (extractable with $NH_4NO_3$), 'exchangeable' chromate (extractable with phosphate buffer pH 7.2), and these results were compared with the data obtained by extractions with ammonium sulfate, borate buffer pH 7.2, saturated borax pH 9.6, and polyphosphate (Graham's salt). In order to maintain the pH of extractant solution about constant, the concentration of extractant buffer had to be raised to at least 0.5 M. The results strongly depended on the kind of extractant, and the solid: liquid ratio. For most of the samples investigated, the extraction efficiency increased in the order borate-sulfate-nitrate-phosphate. Whereas the recovery of $K_2CrO_4\;and\;CaCrO_4$ added to the samples of basic slags prior to the extraction was about complete, the recovery of added $PbCrO_4$ was highly variable. In soil extracts, the color reaction was interfered from co-extracted humics, which react with the chromate in weak acid solution during the time period necessary for color reaction (1 hour). However, this problem can be overcome by standard addition and subtraction of the color of the extractant solution. In soil extract of about pH < 7, organic material reduced chromate during the extraction period also, and standard addition of soluble chromate is recommended to prove recovery and the stability of chromate in the samples. In admixtures of soils and basic slags, results for hexavalent chromium were lower than from the mere basic slags. This effect was more pronounced in phosphate than in nitrate extracts. As a proficiency test, samples low in organic carbon from contaminated sites in Hungary were tested. The results from $NH_4NO_3$ extracts satisfactorily matched the results of the Hungarian labs obtained from $CalCl_2$ extractants.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.6
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• pp.973-982
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• 2012

Crop safety in heavy metal contaminated agricultural field has been a critical issue in Korea and various remediation methods are proposed for minimizing heavy metal transfer from soil to crops. The main objective of this research was to evaluate remediation efficiency of two chemical amendments, lime and steel slag, and to decide extractant for assessing bioavailability of heavy metals. In order to select optimum extractant for evaluating bioavailability of heavy metals, four different single extractants, HCl, DTPA, $CaCl_2$, $NH_4NO_3$, and sequential extraction method were examined. Both chemical amendments showed high immobilization effect for Cd (66%, $33.62mg\;kg^{-1}$) and Pb (74%, $27.65mg\;kg^{-1}$) in soil by HCl extractant. In terms of heavy metal concentration in rice grains, concentrations for Cd (77%, $0.023mg\;kg^{-1}$) and Pb (82%, $0.039mg\;kg^{-1}$) decreased, with addition of chemical amendments. HCl, DTPA, and sequential extractant showed the higher correlation between heavy metal concentration in soil and crops than others. These results indicated that they could be used for assessing bioavailability of heavy metals.

• Journal of Korea Soil Environment Society
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• v.2 no.2
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• pp.53-60
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• 1997

A series of batch and lab-scale pilot tests were conducted to optimize the design parameters for the application of soil washing techniques to the soil contaminated by heavy metals. Cu, Pb, and Zn were selected as target heavy metals. The concentrations of Cu, Pb, and Zn were 500mg/kg dry soil, 1, 000mg/kg dry soil, and 500mg/kg dry soil, respectively. Citric acid and oxalic acid were used for the extractants. In the batch tests, the extraction efficiencies for Cu, Pb, and Zn were 79%, 72%, 72%, respectively. The proper extractant concentration and dilution ratio(weight/volume) for Cu and Pb were turned to be citric acid 50mM and 1:5, respectively. The extraction efficiencies were enhanced with the addition of 1~2% OA-5 or SDS. From pilot scale tests for Pb, first stage and second stage of soil washing resulted in the extraction efficiency of 59% and 78%, respectively.

• Journal of Soil and Groundwater Environment
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• v.15 no.5
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• pp.23-31
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• 2010

For an efficient remediation of Pb-contaminated soil (S-1) in a clay shooting range, a soil washing test was performed with mineral acid, organic acid, chelating agent, and chloride. The Pb extraction efficiency of extractant (0.1 M) used in the washing test showed the order of HCl > $Na_2$-EDTA > NTA > DTPA > citric acid > malic acid > succinic acid > acetic acid > $CaCl_2$ > $MgCl_2$, for S-1 soil. As compared to initial Pb concentration, extraction efficiency by the concentration of extractant was 93.35%, 80.80%, 73.92%, and 24.57% in S-1 soil for HCl (0.5 M, pH 1.10), $Na_2$-EDTA (0.01 M, pH 3.99), citric acid (0.5 M, pH 1.27), and $MgCl_2$ (0.1 M, pH 8.82), respectively. S-1 soil had 56.83% of residue form and 43.17% of non-residue form (18.04% of exchangeable form), respectively. Although the concentrations of these fractions sharply decreased after HCl washing, since the exchangeable forms with relatively large mobility are still distributed as high as 18.78% (to Pb total content in residual soils) in S-1 soil, it is necessary to devise a proper management plan for residual soils after soil washing application.

• Korean Journal of Soil Science and Fertilizer
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• v.42 no.6
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• pp.513-521
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• 2009

The primary goal of this research was to develop an optimized analytical procedure for soil analysis based on ion-selective microelectrodes for agricultural purposes, which can perform on-site measurement of various ions in soil easily and rapidly. For the simple and rapid on-site diagnosis, an analysis of soil chemicals was performed employing a multicomponent-in-situ-extractant and an evaluation of ionselective microelectrodes were conducted through the regressive correlation method with a standard analytical approach widely employed in this area. Examination of sensor responses between various soil nutrient extractants revealed that 0.01M HCl and 1M LiCl provided the most ideal Nernstian response. However, 1M LiCl deteriorated the selective response for analytes due to high concentration (1M) of lithium cation. Thus, employing either 0.1M HCl as an extractant followed by 10 times dilution, or 0.01M HCl as an extractant without further dilution was chosen as the optimal extractant composition. A study of regressive correlation between results from ion-selective microelectrodes and those from the standard analytical procedure showed that analyses of $K^+$, $Na^+$, $Ca^{2+}$, and $NO_3{^-}$ showed the excellent consistency between two methods. However, the response for $NH_4{^+}$ suffered the severe interference from $K^+$. In addition, the selectivity for $Mg^{2+}$ over $Ca^{2+}$ was not sufficient enough since available ionophores developed so far do not provide such a high selectivity for $Mg^{2+}$. Therefore, as an agricultural on-site diagnostic instrument, the device in development requires further research on $NH_4{^+}$ analysis in the soil sample, development of $Mg^{2+}$-selective ionophore, and more detailed study focused on potassium, one of the most important plant nutrients.

• Journal of Soil and Groundwater Environment
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• v.24 no.6
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• pp.1-8
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• 2019

This study evaluated the relative extraction ratio (RER) of As and heavy metals (Cd, Cu and Pb) in paddy soils using the two types extractant, 0.05 M EDTA and 0.43 M HNO₃. The RER was calculated by dividing the concentrations of metals obtained by 0.05 M EDTA or 0.43 M HNO₃ extraction by those obtained by aqua regia extraction. The RER of 0.43 M HNO₃ was larger than that of 0.05 M EDTA. Correlation analysis indicated there was statistically significant correlation (p<0.001) between the concentration in aqua regia and 0.05 M EDTA or 0.43 M HNO₃. Especially, Cd showed the higher correlation than other metals. Stepwise multiple linear regression analyses indicated soil pH, CEC, organic matter content, and soil texture all influenced the metal extraction rates and bioavailability of the metals.

• Korean Journal of Soil Science and Fertilizer
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• v.14 no.4
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• pp.230-235
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• 1982

This study was carried out to select the most effective extractant for Cd analysis in the condition of Korean paddy soil. The various extractants were compared with 0.1 N-HCL common extractant used in Korea. Soil and rice samples were collected at same plot from paddy field adjacent to zinc mining sites. The results ob.tained are as follows. 1. The extractants were able to be arranged in order of higher extractability of cadmium content; 1N-HCL > 0.1N-HCL > 0.075N-Mixture > $1N-NH_4OAC(pH4.8)$ > $DTPA-CaCl_2$ > 5% Acetic acid> $1N-NH_4OAC(pH7.0)$ > $1N-NH_4NO_3$. 2. Although all extractants showed highly significant correlation between Cd content in soil and that in brown rice, $1N-NH_4OAC(pH7.0)$ was considered to be best. 3. The relationship between Cd concentration in soil by extractants and that in brown rice was varied depending on the levels of total Cd content and soil texture. 4. The best extractant under the soil corntions such as total Cd contents and soil texture believed to be $1N-NH_4OAC(pH7.0)$ but Cd concentration extracted in soil was low. 5. The extractant of 0.075N-Mixture was found to be a recommendable one, because it was simillar to 0.1N-HCL in extracting capacity and showed the better correlation between Cd content in soil and brown rice compared to the latter.