• Journal of the Korean Geographical Society
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• v.49 no.2
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• pp.221-244
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• 2014

We suggested several implications by examining geochemical properties of sediments in Simjeok, Jangdo, and Hwaeomneup mountain wetlands which are natural preservation areas. Geochemical properties of wetland sediments show that all wetlands were included in the type of fens, but their distribution patterns were different from one another. We classified three sub-groups of sediments using the two step cluster analysis on the ratio of exchangeable cations. Wetland sediments can be grouped into Ca-dominated, Mg-dominated, and K-dominated types. Simjeok wetland have Ca-dominated sediments, while the sediments of Jangdo wetland indicate the Mg-dominated and Ca-dominated characteristics. Hwaeomneup wetland is composed of K-dominated sediment mainly. Different properties in the ratio are affected by various environmental factors such as geological, pedological, and vegetational settings. Because these geochemical properties will be affected by climate change and human impacts, these will be environmental indicator in mountain wetlands and be used in wetland management. This scheme can be used for classification of mountain wetlands. Therefore, we should work on geochemical properties of wetland sediments and classification schemes based on geochemical properties not only to widen understanding in geomorphic system or ecosystem of mountain wetlands but to conserve mountain wetlands properly.

• Korean Journal of Environmental Agriculture
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• v.22 no.3
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• pp.177-184
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• 2003

Although clay can sorb significant amounts of inorganic contaminants from soils and wastewater, the hydration of exchangeable cations in clay minerals makes it hydrophilic at the clay mineral surfaces and interlayers. Thus, natural clays are often ineffective in complexing and stabilizing toxic organic contaminants in soils and groundwater environment. But, substituting these hydrated cations with cationic surfactant such as QAC(Quaternary ammonium Compound) can change the natural clay from hydrophilic to hydropobic. Furthermore functionalized organoclay can act as a powerful dual function sorbent for both toxic metals and organic compounds. It also can be used as landfill clay liners, slurry walls, nano-composite materials, petroleum tank farms, waste treatment, and filter systems. To use this modified clay minerals effectively, it is required to understand the fundamental chemistry of organoclay, synthetic procedures, its engineering application, bioavailability of sorbed ion-clay complex, and potential risk of organoclay. In this review, we investigate the use, application and historical background of the organoclay in remediation technology. The state-of-the-art of organoclay research is also discussed. Finally, we suggest some future implications of organoclay in environmental research.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.4
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• pp.341-346
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• 2016

This study was conducted to analyze soil physico-chemical properties of agricultural land composed from the river-bed sediments. We investigated the changes of soil physico-chemical properties at 30 different sampling sites containing paddy, upland and plastic film house from 2012 to 2015. pH, exchangeable calcium and magnesium decreased gradually in paddy soils during the four years, whereas the available $P_2O_5$, exchangeable Ca, Mg and EC increased in upland and plastic film house soil. For the soil physical properties, bulk density and hardness of topsoil were $1.47g\;cm^{-3}$ and 21.5 mm and those of subsoil were $1.71g\;cm^{-3}$ and 25.7 mm in paddy soils. In upland soils, bulk density and hardness of topsoil were $1.48g\;cm^{-3}$ and 15.9 mm and those of subsoil were $1.55g\;cm^{-3}$ and 16.9 mm. In plastic film house soils, bulk density and hardness of topsoil were $1.42g\;cm^{-3}$ and 14.4 mm and those of subsoil were $1.40g\;cm^{-3}$ and 18.5 mm, respectively. The penetration hardness was higher than 3 MPa below soil depth 20 cm, and it is impossible to measure below soil depth 50 cm. As these results, in agricultural anthropogenic soils dredged from river basins, the pH, amount of organic matter and exchangeable cations decreased and soil physical properties also deteriorated with time. Therefore, it is needed to apply more organic matters and suitable amount of fertilizer and improve the soil physical properties by cultivating green manure crops, deep tillage, and reversal of deep soils.

• Korean Journal of Soil Science and Fertilizer
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• v.42 no.spc
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• pp.33-39
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• 2009

The practice of supplying nutrients for paddy soil with sustaining human health and ecological soundness is to utilize indicators considering soil chemical reactions. The long-term basis experiment of fertilizer and amendment of paddy soil and an experiment of yield response of soil types on nitrogen level from 2000 till 2002were used to search indicators of nutrient supplying capacity related to soil chemical reactions. Chemical reactions of paddy soil was composed of dissociating and/or adsorbing nutrients and of decomposing soil organic matter (SOM) into $H^+$, $e^-$, $CO_2$ in paddy soil. The indicators of nutrient supplying capacity, which were established by considering soil chemical reactions, were SOM or soil protein for nitrogen and available phosphate for phosphorus and cation exchangeable capacity (CEC) and exchangeable potassium for potassium. Korea has used fertilizer recommendation equations established with the indicators of nutrient supplying capacity for paddy soil.

• Journal of Ecology and Environment
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• v.32 no.4
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• pp.295-304
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• 2009

To understand the properties of soil in Dokdo, we collected soil samples from 12 locations on Seodo and 23 locations on Dongdo, in Dokdo of Gyeongsangbuk-do Province in 2007-2008 and analyzed the soil's physical and chemical characteristics. Sand comprises the largest component (49.37%) of Dokdo soil, followed by silt (40.70%) and clay (9.93%). The soil structure consists mostly of sand loam, followed by loam and silt loam. The pH level of soils from Dokdo varied dramatically among sampling sites and seasons, ranging from 3.36 to 8.02. The total ion content of Dokdo soil also varies greatly among survey places and periods, but in general the total ion content was high in summer when vegetation develops, and low in spring. The exchangeable cation contents of the soil showed low levels in samples where the soil pH was low, including habitats dominated by Agropyron tsukushiense var. transiens and Echinochloa crus-galli, whereas the exchangeable cation contents were high where the organic contents were high, as in habitats dominated by Liriope platyphylla and Artemisia japonica subsp. littoricola. Soil N contents varied greatly among survey sites and higher N contents were found in soil inhabited by Chenopodiaceous plants than in habitats inhabited by other plants. The substantial differences in phosphorus contents among sites were related to excrement of black-tailed gulls. To understand the basic physical and chemical features of the soil on Dokdo, it will be necessary to conduct seasonal and long-term research on soil pH, ion contents, organic contents, N and P, as well as obtaining precise data from samples collected at different depths.

• Korean Journal of Environmental Agriculture
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• v.24 no.4
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• pp.326-333
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• 2005

To enhance groundwater quality and soil nutrient management in fertigated plastic film house, groundwater samples from Jinju 52, Sacheon 3, Changnyeong 3, Sancheong 4 and Namhae 2 sites and soil samples from Jinju 23 sites were collected from September to November in 2004. The average concentration of $NO_3-N$ in groundwater was $12.0mg{\ell}^{-1}$ and 20% of survey sites exceeded the limiting level $(20mg{\ell}^{-1})$ of agricultural goundwater quality. The amount of ions in groundwater was in the order of $Ca^{2+}>Na^+>Mg^{2+}>NH_4-N>K^+$ in cations and ${HCO_3}^->{SO_4}^{2-}>NO_3-N>Cl^-$ in anions. Electrical conductivity of groundwater was positively correlated with $Ca^{2+},\;Cl^-,\;Mg^{2+},\;{SO_4}^{2-},\;NO_3-N\;and\;Na^+$ concentrations. In addition, it had significantly positive correlation with sum cations and anions, respectively $({\Sigma}cations\;(me{\ell}^{-1})$ = EC values $(dS\;m^{-1}){\times}4.65,\;{\Sigma}anions\;(me{\ell}^{-1})$ = EC values $(dS\;m^{-1}){\times}7.63\;and\;{\Sigma}\;(cations+anions,\;me{\ell}^{-1})$ = EC values $(dS\;m^{-1}){\times}11.1)$. The proportions of soil chemical properties over the critical levels for crop production in fertigated plastic film house were 56.5% in pH, 47.8% in OM, 95.7% in available $P_2O_5$, 78.3% in exchangeable K, 87% in exchangeable Ca, 56.5% in exchangeable Mg and 43.5% in EC. Soil pH was positively correlated with pH $(r=0.540^{**})$ and ${HCO_3}^-$ concentration $(r=0.523^{**})$ of groundwater.

• Korean Journal of Soil Science and Fertilizer
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• v.13 no.3
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• pp.77-83
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• 1981

In order to obtain an imformation on the exchangeable potassium and it's activity ratio to other cations in wet paddy top soil grown by rice, soil samples were taken from bottomless middle size (60cm in dia, and height, respectively) round concrete pot being car ride out with an experiment on the split application of potassium in relation to lime and analysed. The pot experiment was being conducted from 1974 at a farm of the City University of Seoul and the wet soil samples were taken from the paddy in the year of 1976. The samples were extracted with $0.1N-AlCl_3$ solution and analysed regarding the elements. Results obtained are as follows : 1. Less exchangeable potassium was extracted from the soils limed than those unlimed when the same amount of potassium was applied immediatly after flooding. However, when the Potassium was applied two weeks after flooding, the reverse was observed. The fact that the exchangeable potassium is increased in the case that potassium fertilizer applied two weeks after flooding explained as due either to the prohibiting effect of iron or less abserption of potassium by the crop. 2. A remarkable decrease of exchangeable potassium of soils was observed during the vigorous growth stage of rice. 3. The activity ratio of $\frac{K}{(Fe^{{+}{+}}){\frac{1}{2}}}$ was remarkabley low after July 16th at which the soil was considerably reduced. 4. The activity ratio $\frac{K^+}{NH^+}$ of limed soil lasted highly until July 16th. It may be resulted from slow progress of ammonification caused by high pH. 5. A positive correlation was found between $Fe^{{+}{+}}$ and $Ca^{{+}{+}}$ under reduced condition. But there was no correlation between $Fe^{{+}{+}}$ and $K^+$ or $NH^+_4$, because that the concentrations of $K^+$ and $NH^+_4$ in soil fluctuates during growing season.

• Proceedings of the Korean Geotechical Society Conference
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• 1997.10a
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• pp.19-36
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• 1997

This paper discusses the reduction and subsequent recovery and increase of shear strength of clay in the vicinity of soil-cement column. Laboratory and field tests were conducted to investigate the effects on surrounding clay during and after soil-cement column installation in soft Ariake clay. Discussions were made on the mechanism of strength changes of clay by considering the thixotropic recovery, reconsolidation effect, penetration of cement slurry and diffusion of exchangeable cations. On the basis of field and laboratory observations, 10 days after column installation, the decreased shear strength of surrounding clay during mixing was recovered and 30 days later, shear strength of surrounding clay increased 30% by average. Therefore, it is recommended that the increase of shear strength of clay can be taken into consideration in the bearing capacity and stability analysis of the composite ground.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.19 no.3
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• pp.331-338
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• 2021

Extensive studies have been conducted on thermal conductivity of bentonite buffer materials, as it affects the safety performance of barriers engineered to contain high-level radioactive waste. Bentonite is composed of several minerals, and studies have shown that the difference in the thermal conductivity of bentonites is due to the variation in their mineral composition. However, the specific reasons contributing to the difference, especially with regard to the thermal conductivity of bentonites with similar mineral composition, have not been elucidated. Therefore, in this study, bentonites with significantly different thermal conductivities, but of similar mineral compositions, are investigated. Most bentonites contain more than 60% of montmorillonite. Therefore, it is believed that the exchangeable cations of montmorillonite could affect the thermal conductivity of bentonites. The effect of bentonite type was comparatively analyzed and was verified through the effective medium model for thermal conductivity. Our results show that Ca-type bentonites have a higher thermal conductivity than Na-type bentonites.

• Korean Journal of Soil Science and Fertilizer
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• v.31 no.3
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• pp.246-252
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• 1998

A survey was conducted to investigate the status of soils involving pH, electrical conductivity, total organic matter content, available phosphate and major exchangeable cations in the paddy soils sampled from 1,168 sites throughout the country. The content of soil chemical properties was lower on the average than the optimum levels for cropping. An average value showed pH 5.6, organic matter $25g\;kg^{-1}$, available phosphate $128mg\;kg^{-1}$, available silicate $72mg\;kg^{-1}$, and exchangeable potassium and the calcium and magnesium were 0.32, 4.0, $1.2cmol^+\;kg^{-1}$, respectively. Soil chemical properties was related with topography except soil pH. A soil pH and organic matter, available phosphate, exchangeable potassium increased with time while exchangeable calcium, magnesium available silicate decreased with time.