• Economic and Environmental Geology
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• v.45 no.2
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• pp.121-135
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• 2012

Soil dispersion and heavy metal leaching with two heavy metal-contaminated soils were studied to derive the optimal dispersion condition in the course of developing the remedial technology using magnetic separation. The dispersion solutions of pyrophosphate, hexametaphosphate, orthophosphate and sodium dodecylsulfate (SDS) at 1 - 200 mM and the pH of solutions was adjusted to be 9 - 12 with NaOH. The clay content of suspension as an indicator of dispersion rate and the heavy metal concentration of the solution were tested at the different pHs and concentrations of the dispersion solution during the experiment. The dispersion rate increased with increasing the pH and dispersion agent concentration of the solution. The dispersion efficiency of the agents showed as follows: pyrophosphate > hexametaphosphate > SDS > orthophosphate. Arsenic leaching was sharply increased at 50 mM of phosphates and 100 mM of SDS. The adsorption of $OH^-$, phosphates and dodecysulfate on the surface of Fe- and Mn-oxides and soil organic matter and the broken edge of clay mineral might decrease the surface charge and might increase the repulsion force among soil particles. The competition between arsenic and $OH^-$, phosphates and dodecylsulfate for the adsorption site of soil particles might induce the arsenic leaching. The dispersion and heavy metal leaching data indicate that pH 11 and 10 mM pyrophosphate is the optimum dispersion solution for maximizing dispersion and minimizing heavy metal leaching.

• Korean Journal of Soil Science and Fertilizer
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• v.24 no.2
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• pp.95-101
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• 1991

The results of relationships between colloidal stability and soil pH on three Hawaii's volcanic ash soils developed under the three different rainfall conditions can be summarized as follows: 1. The Hilo soil only revealed the increase of colloidal stability by becoming for from Z.P.C point to either side of pH. 2. Hilo and Kawaihae soils, however, showed the increase of colloidal stability only in the higher pH range than their Z.P.C. 3. $P_2O_5$ drying procers decreased colloidal stability kof these soils because of so called irreversible drying characteristics of amorphous materials and the decrement was in order of: Akaka>Hilo>Kawaihae expressing positive correlation with content of amorphous materials in them. 4. The difference of colloidal stability curves among three soils can easily be interpreted by DLVO theory considering 0.1N-HCl amount added to decrease their soil pH, respectively. The addition of large amount of 0.1N-HCl into Akaka and Kawaihae soils did not effectively develop the positive charge but resulted in the shrink of diffuse double layer thickness inducing large attraction forces among soil particles.

• Korean Journal of Soil Science and Fertilizer
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• v.13 no.2
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• pp.65-70
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• 1980

This experiment was aimed at selecting the most suitable dispersing agent to the Korean soils. The particle size distribution of 18 soil samples representing the great soil groups in Korea was analysed with 5 different dispersing agents by pipette-method. Passing percent of 0.05, 0.02 and 0.002mm in diameter was used for the comparision of the dispersion capacity of chemical agents. The results obtained are as follows; 1. The influence of chemical agents on dispersion seemed to be greater to finer soil particles. The passing percents of 0.002mm showed a great differences according to the chemical agents used, while little differences was observed in those of 0.05mm. 2. It was showed that sodium pyrophosphate had the highest dispersion capacity for the most of Korean soils, the dispersion capacity of sodium hexametaphosphate was also high enough except for volcanic ash soils. 3. It was recommendable that sodium hexametaphosphate could widely be used as a dispersing agent in the routine analysis of soil particle size distribution except for the Volcanic ash soils. 4. The dispersion of Volcanic ash soils was rather poor when chemical agents used. Therefore, special care should be taken for the dispersion of allophane soils.

• Journal of Soil and Groundwater Environment
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• v.11 no.6
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• pp.28-34
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• 2006

Laboratory column tests using $Cl^-$ tracer were conducted to study the correlation of soil particle distribution and hydrodynamic dispersion mechanism with three kinds of ununiformed soil samples, in which the ratio of gravel and sand versus silt and clay is 24.5 for S-1 soil, 4.48 for S-2 soil, and 0.4 for S-3 soil. Chloride breakthrough curves with time were fitted with gaussian functions. The relative concentrations of chloride were converged to 1.0 after 0.7 hours for S-1, 6.3 hours for S-2, and 389 hours for S-3. Average linear velocity, longitudinal dispersion coefficient, and longitudinal dispersivity were calculated by chloride breakthrough curves. Longitudinal dispersion coefficients were $1.20{\times}10^{-4}\;m^2/sec$ for S-1, $8.87{\times}10^{-7}\;m^2/sec$ for S-2, and $1.94{\times}10^{-9}\;m^2/sec$ for S-3. Peclet numbers calculated by the molecular diffusion coefficient of chloride and the mean grain diameters of soils were $2.59{\times}10^2$ for S-1, $6.27{\times}10^0$ for S-2, and $1.35{\times}10^{-4}$ for S-3. Mechanical dispersion was dominant for the hydrodynamic dispersion mechanism of S-1. Both mechanical dispersion and molecular diffusion were dominant for the hydrodynamic dispersion mechanism of S-2, but mechanical dispersion was ascendant over molecular diffusion. Hydrodynamic dispersion in S-3 was occurred mainly by molecular diffusion. When plotting three soils on the graph of $D_L/D_m$ versus Peclet number produced by Bijeljic and Blunt (2006), the values of $D_L/D_m$ for S-1 and S-2 were more than 2.0 order compared to their graph. S-3 was not plotted on their graph because the Peclet number was as small as $1.35{\times}10^{-4}$.

• Journal of Korea Water Resources Association
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• v.31 no.6
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• pp.795-806
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• 1998

Soil moisture is affected by regional climate, soil characteristics and land surface condition, etc,. Especially, the changes in land surface condition is more than other factors, which is mainly due to rapid urbanization and industrialization. This study is to evaluate how the change of land surface condition impacts on soil moisture field evolution using a simple model of soil moisture dynamics. For the quantification of soil moisture field, the first half of the paper is spared for the statistical characterization based on the first- and second-order statistics of Washita '92 and Monsoon '90 data. The second half is for evaluating the impact of land cover changes through simulation study using a model for soil moisture dynamics. The model parameters, the loss rate and the diffusion coefficient, have been estimated using the observed data statistics, where the changes of surface conditions are considered into the model by applying various parameter sets with different second-order statistics. This study is concentrated on evaluating the impact due to the changes of land surface condition variability. It is because we could easily quantify the impact of the changes of its areal mean based on the linear reservoir concept. As a result of the study, we found; (1)as the variability of land surface condition, increases, the soil moisture field dries up more easily, (2)as the variabilit y of the soil moisture field is the highest at the beginning of rainfall and decreases as time goes on to show the variability of land surface condition, (3)the diffusion effect due to surface runoff or water flow through the top soil layer is limited to a period of surface runoff and its overall impact is small compared to that of the loss rate field.

• The Journal of Engineering Geology
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• v.16 no.1 s.47
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• pp.15-21
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• 2006

Sandy soils obtained from the field were examined by the way of particle analyses. The hydraulic conductivity values of the disturbed soil samples were measured by the falling head method. Then the correlations between the hydraulic conductivity and particle distribution were defined. The soil which was a product of the weathering of the granitic rocks belonged to sand and loamy sand area in a sand-silt-clay triangular diagram. The measurements of hydraulic conductivity were $1.15X10^{-5}\sim7.31X10^{-4}cm/sec$ which is the range of sand and silt. It was clearly observed that the hydraulic conductivity measurements of the sandy soils showed stronger correlations with the particle variances rather than the mean grain sizes. The larger the variances, the smaller the hydraulic conductivity measurements. The sandy soil which was a product of weathered granite and whose mean grain size was $0.38\sim1.97mm$ showed regression curves of $y=6.0E-5x^{-1.4}$ in a correlations between hydraulic conductivity and particle variances. Accordingly, it is clearly concluded that making estimates with-out any consideration about particle variances can produce serious errors.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2001.09a
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• pp.239-243
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• 2001

대수층에서 오염물질의 이동은 대류, 확산, 흡착 등의 물리화학적 현상에 영향을 받는다. 지하수 유동과 오염 물질 운송에 관련된 분석은 지하수 자원의 관리와 평가, 복원사업에 필요한 요소이다. 본 연구의 목적은 사질대수층에서의 2차원 plume 모니터링을 통하여 오염운의 관측치와 모사치를 비교하므로써 종분산지수와 종/횡분산지수비를 결정하는 것이다. 실내 자유면 대수층 실험에서 MT3D를 이용한 case study로부터 추정된 종분산지수는 0.4 cm였으며 횡/종분산지수비는 1/5로 나타났다.

• Korean Journal of Soil Science and Fertilizer
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• v.40 no.1
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• pp.57-63
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• 2007

Soil aggregation has been considered as an important factor not only for increasing soil productivity and soil quality but also improving nutrient use availability and water use efficiency. However, the relationship between soil aggregation and soil properties hasn't well reported for Korean soils. Objective of this research was to identify the relationship among soil water-stable aggregate (WSA), soil properties and soil dispersion ratio. Soil samples were analyzed for water-stable aggregate, Middleton's dispersion ratio, and soil physical and chemical properties. Water-stable aggregate was significantly correlated to soil textural properties, soil organic matter, and exchangeable cations. Middleton's dispersion ratio was significantly correlated with water-stable aggregate ($r=-0.76^{***}$). Regression equation for water-stable aggregate was estimated by Middleton's dispersion ratio (Y=-0.79X + 96.49; $r^2=0.58^{**}$). In this research, we conclude that water-stable aggregate was significantly correlated with some soil properties and was able to be estimated by rapid and easily measurable Middleton's dispersion ratio.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1999.10a
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• pp.61-64
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• 1999

산성침출수에 의한 광산폐기물 매립지 근처의 지하 환경의 오염 및 대처 방안의 효과를 수치적으로 예측하였다. 이를 위하여 지하토양에서 Darcy 법칙을 사용한 침출수의 흐름과 이산-분산에 의한 오염물질의 이동현상을 예측하기 위하여 Galerkin 유한요소법을 활용하였다. 토양오염의 지연을 위하여 석회석 차수막을 연직형과 수평형을 도입하여 그 효과를 조사하였다. 수평차수막에서의 수착이 오염물질의 이동을 지연시키는데 상당한 효과가 있는 것으로 나타났다. 반면에 연직차수막은 지하수의 우회유동으로 인한 오염물질의 확산이 가중되고 있는 것으로 예측되었다. 전반적으로 침출수의 흐름은 광산매립지 제방 근처에서 강하게 일어나는 것으로 나타났다. 이를 근거로 차수막의 효과적인 설치방안이 고안되어야 할 것으로 보인다.

• Korean Journal of Environmental Agriculture
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• v.37 no.4
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• pp.317-323
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• 2018

BACKGROUND: This study was conducted to evaluate the water-dispersible clay content of paddy soils over the country in the summer rainy season as affected by cultivated years using heavy agro-machinery and soil properties such as texture and exchangeable sodium percentage. METHODS AND RESULTS: Water-dispersible clay content of 16 soil series of Korean paddy soils over the country were investigated in summer rainy season from July to August, 2006 by Middleton's method. Water-dispersible clay content ranged from non-detected to 4.8%, showing maximum value from the fine textured soils and high clay dispersibility in average from the coarse textured soils. Longer cultivated years using agro-machinery more than 40 hp result in higer water-dispersible clay content for 60% of studied paddy soils with less than 5% of exchangeable sodium percentage (ESP). Exceptionally, soils with relatively big difference of ESP at about 10 percent showed higher water-dispersible clay content with higher ESP. CONCLUSION: Long years of cultivation using agro-machinery with more than 40 hp enhanced water-dispersiblility of clay in approximately 60% of the studied paddy fields except for salt-affected soils.