• Title, Summary, Keyword: Transport in soil

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The Characteristics of Bioremediation for VOCs in Soil Column (VOCs처리를 위한 미생물의 토양복원화 특성)

  • 손종렬;장명배
    • Proceedings of the Korean Environmental Health Society Conference
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    • pp.9-12
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    • 2002
  • Diffusive transport of volatile organic compounds(VOCs) and their degradation by bacteria in unsaturated soils are couple by poorly understood mass transfer kinetics at the gas/water interface. Determination of the fate of VOCs in unsaturated soil is necessary to evaluate the feasibility of natural attenuation as a VOC remediation strategy. The objective of this study was to develop a mechanistically based mathematical model that would consider the interdependence of VOC transport, microbial activity, and sorptive interaction in a moist, unsaturated soil. Because the focus of the model was on description of natural attenuation, the advective VOC transport that is induced in engineered remediation processes such as vapor extraction was not considered. The utility of the model was assessed through its ability to describe experimental observations form diffusion experiments using toluene as a representative VOC in well-defined soil columns that contained a toluene degrading bacterium, Pseudomonas Putida, as the sole active microbial species. The coefficient for gas-liquid mass-transfer, K$\sub$LA/, was found to be a key parameter controlling the ability of bacteria to degrade VOCs. This finding indicates that soil size and geometry are likely to be important parameters in assessing the possible success of natural attenuation of VOCs in contaminated unsaturated soils.

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Comparison of Contaminant Transport between the Centrifuge Model and the Advection Dispersion Equation Model

  • Young, Horace-Moo;Kim, Tae-Hyung
    • Journal of Soil and Groundwater Environment
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    • v.8 no.3
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    • pp.8-12
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    • 2003
  • The centrifuge test result on capped sediment was compared to the advection- dispersion equation proposed for one layered to predict contaminant transport parameters. The fitted contaminant transport parameters for the centrifuge test results were one to three orders of magnitude greater than the estimated parameters from the advection-dispersion equation. This indicates that the centrifuge model over estimated the contaminant transport phenomena. Thus, the centrifuge provides a non-conservative approach to modeling contaminant transport. It should be also noted that the advection-dispersion equation used in this study is a one layered model. Two layered modeling approaches are more appropriate for modeling this data since there are two layers with different partitioning coefficients. Further research is required to model the centrifuge test using two-layered advection-dispersion models.

Breakthrough Curves and Miscible Displacement of Cadmium Through Double-Layered Reclaimed Soils Amended with Macroporous Granule

  • Kim, Hye-Jin;Ryu, Jin-Hee;Kim, Si-Ju;Park, Mi-Suk;Chung, Doug-Young
    • Korean Journal of Soil Science and Fertilizer
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    • v.44 no.1
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    • pp.15-21
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    • 2011
  • Transport of heavy metals such as Cd is affected by several rate-limiting processes including adsorption and desorption by exchange reactions in soils. In this study, column transport and batch kinetic experiments were performed to assess Cd mobility in a double-layered soil with a reclaimed saline and sodic soil (SSS) as top soil and macroporous granule (MPG) as a bottom layer. For individual soil layer having different physical and chemical properties, Cd was considered to be nonlinear reactivity with the soil matrix in layered soils. The dispersive equation for reactive solutes was solved with three types of boundary conditions for the interface between soil layers. The adsorption of Cd with respect to the saline-sodic sandy loam and the MPG indicated that the nature of the sites or the mechanisms involved in the sorption process of Cd was different and the amounts of Cd for both of samples increases with increasing amounts of equilibrium concentration whereas the amount of Cd adsorbed in saline-sodic sandy loam soil was higher than that in MPG. The results of breakthrough curve indicating relative Cd retardation accompanied by layer material and sequence during leaching showed that the number of pore volumes to reach the maximum relative concentration of 1 increased in the order of MPG, SSS, and double layer of SSS-MPG. Breakthrough curves (BTCs) from column experiments were well predicted with our double-layered model where independently derived solute physical and retention parameters were implemented.

Multiphase Modeling on the Convective Transport of an Organic Solvent through Unsaturated Soils (비포화 토양층 내 유기 용매의 이류 이동에 대한 다상 모델링)

  • Lee Kun Sang
    • Journal of Soil and Groundwater Environment
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    • v.9 no.3
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    • pp.20-26
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    • 2004
  • In-situ photolysis is one of the most promising ways to clean up a soil contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). This study focuses on the mathematical description and model development of the convective upward transport of an organic solvent driven by evaporation and photodecomposition at the surface as the major transport mechanism in the clean up process. A finite-element-based numerical model was proposed to incorporate effects of multiphase flow on the distribution of each fluid, gravity as a driving force, and the use of van Genutchen equation for more accurate description of k-S-p relations. This paper presents results of extensive numerical calculations conducted to investigate the various parameters that play a role in the solvent migration through a laboratory-scale unsaturated soil column. The numerical results indicate that gravity affects significantly on the fluids distribution and evaporation for highly permeable soils. The soil texture has a profound influence on the fluid saturation profile during evaporation process. The amount of solvent convective motion increases with increasing evaporation rates and decreasing initial water saturation. Simulations conducted in this study have shown that the developed model is very useful in analyzing the effects of various parameters on the convective migration of an organic solvent in the soil environments.

Modeling Fate and Transport of Organic and Nitrogen Species in Soil Aquifer Treatment-(I) Model Development and Verification (토양/대수층 처리(soil aquifer treatment)에서 유기물과 질소화합물 제거와 이송 모델링-(I) 모델 개발 및 검증)

  • Kim Jung-Woo;Kim Jeong-Kon;Cha Woo-Suk;Choi Hee-Chul
    • Journal of Soil and Groundwater Environment
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    • v.10 no.3
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    • pp.9-15
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    • 2005
  • Soil aquifer treatment is a water reuse technology that secondary or tertiary treated wastewater is infiltrated into the aquifer in which physical and biochemical reactions occur. Major consideration in SAT is the removal and transport of DOC and nitrogen species. In this study, reaction mechanism in SAT was examined considering nitrification, denitrification and organic oxidation. In addition, SAT modeling system was developed as the reaction mechanism was applied to groundwater flow and transport model. In verification of the reaction module by 1-dimensional unsaturated soil column test, the experimental data of all of the species, ammonium, nitrate, DOC and DO, were well matched with the simulation results. In sensitivity analysis, ammonium partition coefficient, dissolved oxygen inhibition constant and biomass decay rate affect ammonium, DOC and DO concentration of effluent, respectively.

The Characteristics of Bioremediation for VOCs in Soil Column (VOCs 처리를 위한 미생물의 토양복원화 특성)

  • 손종렬;장명배;조광명
    • Journal of environmental and Sanitary engineering
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    • v.17 no.1
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    • pp.52-56
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    • 2002
  • The study was carried out to evaluate the characteristics of biodegradation by Pseudomonas putida G7 in soil column. The reactor system was used to investigate mass transfer of VOCs as Toluene in a column of unsaturated soil. Determination of the fate of VOCs in unsaturated soil is necessary to evaluate the feasibility of natural attenuation as a VOCs remediation strategy. The objective of this study was to develop a mechanistically based mathematical model that would consider the interdependence of VOC transport, microbial activity, and sorptive interactions in a moist, unsaturated soil. Because the focus of the model was on description of natural attenuation, the advective VOCs transport that is induced in engineered remediation processes such as vapor extraction was not considered. It can be concluded that the coefficient for gas liquid mass-transfer was found to be a key parameter controlling the ability of bacteria to VOCs. Finally, it appeared that bioremediation technology of VOCs which are difficult to be decomposed by chemical methods.

A Comparative Study of Tracer Tests in Fractured and Porous Media (단열 및 다공질 대수층에서의 추적자 시험연구)

  • 이진용;이지훈;김용철;천전용;이민효;이강근
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • pp.132-135
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    • 2001
  • To understand and compare tracer transport in fractured and porous media. multiple tracer tests were conducted in Wonju and Uiwang sites. The target media were fractured in Wonju site and porous in Uiwang site. It was known that groundwater flow for the two hydrogeologic systems could be represented using a EPM approach. However, the tracer transport in the two aquifer systems was greatly different. In this study, we analyzed the different tracer transport behavior in the two systems, from which our understanding of the tracer dispersion was greatly enhanced. we used bromide and chloride as tracers.

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The Study of Cd and Pb Characteristics on Electrokinetic Remediation of Mine Deposit (Electrokinetic 기법에 의한 광산퇴적토내 Cd과 Pb의 제거 특성에 관한 연구)

  • 윤삼석;신현무;이창언
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • pp.61-64
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    • 2001
  • In the remediation of contaminated soil by electrokinetic process, transport characteristics of contaminants are major factors. Pb is highly fixed to entire soil and not moved readily. High concentration of Cd was analyzed in the cathodic section but anodic section's concentration was lower than initial concentration. Although the Cd had high treatment effect, 50% of total mass was concentrated in cathodic section and was not flowed out readily. Most of transported Cd may be adsorbed in the cathodic side soil due to increased pH at adjacent to catholyte.

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A Study on Transport Characteristics of Fe in Soil (토양 내 철의 이동특성에 관한 연구)

  • Cho, Ki-Chul;Lee, Kyeong-Ho;Choung, Young-Heon;Cho, Sang-Won;Oh, Kwang-Joong
    • Journal of Korean Society of Environmental Engineers
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    • v.27 no.10
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    • pp.1043-1051
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    • 2005
  • In this stduy, adsorption and transport characteristics of Fe in the soil were investigated using convection-dispersion local equilibrium sorption model and two-site non-equilibrium sorption model. In batch experiments with different Fe concentration, characteristics of Fe adsorption was investigated using Freundlich and linear isotherm. Column experiments with different flow rate, organic matter content md Fe concentration were also carried out. We measured Fe concentrations in injection-liquid and in effluent, and then applied them to CXTFIT program. As a result of column experiments, some parameters(D, R, ${\beta}$, ${\omega}$) used in two-site non-equilibrium adsorption model were obtained. Characteristics of Fe transport were analyzed using the parameters(D, R, ${\beta}$, ${\omega}$) obtained from the CXTFIT program, Consequently, characteristics of Fe transport in the soil were predicted through two-site non-equilibrium adsorption model.

Development of Mathematical Model for Both Solute Transport in Snow and Isotopic Evolution of Snowmelt (눈 속에서의 용질이동 및 융설의 동위원소변동에 관한 모델개발)

  • Lee, Jeonghoon
    • Journal of Soil and Groundwater Environment
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    • v.17 no.5
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    • pp.31-39
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    • 2012
  • Chemical and isotopic variations of snowmelt provide important clues for understanding snowmelt processes and the timing and contribution of snowmelt to catchment or watershed in spring. The newly developed model includes a hydraulic exchange between mobile and immobile water (${\omega}$), and isotopic exchanges between both mobile water and ice ($f_1$) and immobile water and ice ($f_2$). Since the new model is based on the mobile-immobile water conceptualization, which is widely used for describing chemical tracer transport in snow, it allows simultaneous calculations of chemical as well as isotopic variations in snowpack discharge. We compare the model results with a study of solute transport and isotopic evolution of snowmelt in snow, using artificial rain-on-snow experiments with conservative anion ($Br^-$). These observations are used to test the newly developed model and to better understand physical processes in a seasonal snowpack where our model simulates the chemical and isotopic variations.