• Title, Summary, Keyword: Transport in soil

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Phenanthrene으로 오염된 불포화토양내에서 오존이동 모델링

  • 정해룡;배기진;최희철
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • pp.86-88
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    • 2002
  • The mathematical model was proposed to simulate ozone transport and remediation in unsaturated soils contaminated with phenanthrene. Soil column experiments were also carried out to calibrate the mathematical model. The experimental results successfully matched with the modeling results in various soil conditions. The model proposed nondimensional fraction factor to reveal reactivity between phenanthrene and gas phase ozone and liquid phase ozone. From sensitivity analysis, the fraction factor and stoichiometric coefficient decreased as water content increased. Simulation results showed increased SOM content retarded the ozone transport and the phenanthrene removal due to increased ozone consumption.

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Multi-Region Model of Solute Transport in Soil for the Preferential Flow (Preferential 흐름에 의한 토양내의 다영역 용질이동 모델)

  • 안병기
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.42 no.2
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    • pp.71-77
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    • 2000
  • A multi-region model for solute transport through saturated soils has been developed to describe preferential flow. The model consists of numerous discrete pore groups, which are characterized by a discrete dispersion coefficient, flow velocity, and porosity . The hydraulic properties for each pore group are derived from a soil's hydraluic conductivity and soil water characteristic functions . Flow in pore group is described by the classical advection-disersion equation (ADE). An implict finite difference scheme was applied to the governing equation that results in a block-tridiagonal system of equations that is very efficient and allows the soil to be divided into any number of pore groups. The numerical technique is derived from methods used to solve coupled equations in fluid dynamics problems and can also be applied to the transport of interacting solutes. The results of the model are compared to the experimental data from published papers. This paper contributes on the characteristics of the method when applied to the parallel porosity model to describe preferential flow of solutes in soil.

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Development a numerical model of flow and contaminant transport in layered soils

  • Ahmadi, Hossein;Namin, Masoud M.;Kilanehei, Fouad
    • Advances in environmental research
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    • v.5 no.4
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    • pp.263-282
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    • 2016
  • Contaminant transport in groundwater induces major threat and harmful effect on the environment; hence, the fate of the contaminant migration in groundwater is seeking a lot of attention. In this paper a two dimensional numerical flow and transport model through saturated layered soil is developed. Groundwater flow and solute transport has been simulated numerically using proposed model. The model implements the finite volume time splitting method to discretize the main equations. The performance, accuracy and efficiency of the out coming numerical models have been successfully examined by two test cases. The verification test cases consist of two-dimensional, groundwater flow and solute transport. The final purpose of this paper is to discuss and compare the shape of contaminant plume in homogeneous and heterogeneous media with different soil properties and control of solute transport using a zone for minimizing the potential of groundwater contamination; furthermore, this model leads to select the effective and optimum remedial strategies for cleaning the contaminated aquifers.

농경지 토양에서 N과 P의 거동 특성

  • 최태범;장윤영;이기철
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • pp.451-454
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    • 2003
  • Nonpoint source pollution of groundwater and subsurface water from irrigated agriculture is a major concern in many areas. In this study we aimed to investigate the effect of the water applied by irrigation in agricultural area on the transport of nitrogen and phosphorus originated from fertilizers applied to the surface of soil in agricultural activities. We first conducted investigation on the resdual concentrations of soil N and P in a selected agricultural area. And simulating the target area by column studies in the laboratory leaching extent of various components from the composite and urea fertilizers applied on the soil surface during irrigation was studied. Infiltration of water enhanced the leaching of nitrogen and phosphorus in both the rice paddy field soil and the patch soil. The downward N and P transport with infiltrating water was more pronounced in the patch soil column and the increased residual concentrations of N and P in the lower sections in the patch soil column was found with time.

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Modeling the sensitivity of hydrogeological parameters associated with leaching of uranium transport in an unsaturated porous medium

  • Mohanadhas, Berlin;Govindarajan, Suresh Kumar
    • Environmental Engineering Research
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    • v.23 no.4
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    • pp.462-473
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    • 2018
  • The uranium ore residues from the legacies of past uranium mining and milling activities that resulted from the less stringent environmental standards along with the uranium residues from the existing nuclear power plants continue to be a cause of concern as the final uranium residues are not made safe from radiological and general safety point of view. The deposition of uranium in ponds increases the risk of groundwater getting contaminated as these residues essentially leach through the upper unsaturated geological formation. In this context, a numerical model has been developed in order to forecast the $^{238}U$ and its progenies concentration in an unsaturated soil. The developed numerical model is implemented in a hypothetical uranium tailing pond consisting of sandy soil and silty soil types. The numerical results show that the $^{238}U$ and its progenies are migrating up to the depth of 90 m and 800 m after 10 y in silty and sandy soil, respectively. Essentially, silt may reduce the risk of contamination in the groundwater for longer time span and at the deeper depths. In general, a coupled effect of sorption and hydro-geological parameters (soil type, moisture context and hydraulic conductivity) decides the resultant uranium transport in subsurface environment.

Transport Characteristics of Cd, Cu and Zn in a Sewage Sludge-Treated Calcareous Soil (하수오니 처리 석회질 토양에서의 Cd, Cu 및 Zn 의 수송 특성)

  • Lee, Sang-Mo;Cho, Chai-Moo
    • Korean Journal of Soil Science and Fertilizer
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    • v.32 no.4
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    • pp.412-420
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    • 1999
  • A controlled column study using elution development and miscible displacement was conducted to assess heavy metal transport characteristics in sludge-untreated soil ("Control"), soil treated with an equivalent of sludge 50 and 100 dry ton $ha^{-1}$ ("Soil-Sludge mixtures"), and sewage sludge ("Sludge"). The elution curves (ECs) and the breakthrough curves (BTCs) for Cd, Cu and Zn in sludge 50 and 100 dry ton $ha^{-1}$ treated soils are not different from the sludge-untreated soil, The ECs for Cd, Cu and Zn in soil column which received a pulse of 10 mg of each Cd, Cu and Zn were similar to those of Cd, Cu and Zn in soil column which had no Cd, Cu and Zn added, but were very different with the ECs for Cd, Cu and Zn in soil column which received a pulse of Cd, Cu and Zn containing 50 mg of each metal. On the other hand, the BTCs for Cd, Cu and Zn in soil columns that were eluted with 500 and $1000mg\;L^{-1}$ of mixed solution of Cd, Cu and Zn were similar to each other, but were distinctly different with the BTCs for Cd, Cu and Zn in soil column that was eluted with $100mg\;L^{-1}$ mixed solution of Cd, Cu and Zn. Sewage sludge applied at rates of 50 and 100 dry ton $ha^{-1}$ did not affect the transport characteristics of this calcareous soil. The apparent mobility for this sludge treated soil and sludge is: Cd >Zn>Cu. The transport characteristics of Cd and Zn are similar to each other, but are different from those of Cu.

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Changes in plant hydraulic conductivity in response to water deficit

  • Kim, Yangmin X.;Sung, Jwakyung;Lee, Yejin;Lee, Seulbi;Lee, Deogbae
    • Proceedings of the Korean Society of Crop Science Conference
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    • pp.35-35
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    • 2017
  • How do plants take up water from soils especially when water is scarce in soils? Plants have a strategy to respond to water deficit to manage water necessary for their survival and growth. Plants regulate water transport inside them. Water flows inside the plant via (i) apoplastic pathway including xylem vessel and cell wall and (ii) cell-to-cell pathway including water channels sitting in cell membrane (aquaporins). Water transport across the root and leaf is explained by a composite transport model including those pathways. Modification of the components in those pathways to change their hydraulic conductivity can regulate water uptake and management. Apoplastic barrier is modified by producing Casparian band and suberin lamellae. These structures contain suberin known to be hydrophobic. Barley roots with more suberin content from the apoplast showed lower root hydraulic conductivity. Root hydraulic conductivity was measured by a root pressure probe. Plant root builds apoplastic barrier to prevent water loss into dry soil. Water transport in plant is also regulated in the cell-to-cell pathway via aquaporin, which has received a great attention after its discovery in early 1990s. Aquaporins in plants are known to open or close to regulate water transport in response to biotic and/or abiotic stresses including water deficit. Aquaporins in a corn leaf were opened by illumination in the beginning, however, closed in response to the following leaf water potential decrease. The evidence was provided by cell hydraulic conductivity measurement using a cell pressure probe. Changing the hydraulic conductivity of plant organ such as root and leaf has an impact not only on the speed of water transport across the plant but also on the water potential inside the plant, which means plant water uptake pattern from soil could be differentiated. This was demonstrated by a computer simulation with 3-D root structure having root hydraulic conductivity information and soil. The model study indicated that the root hydraulic conductivity plays an important role to determine the water uptake from soil with suboptimal water, although soil hydraulic conductivity also interplayed.

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Sediment Erosion and Transport Experiments in Laboratory using Artificial Rainfall Simulator

  • Regmi, Ram Krishna;Jung, Kwansue;Nakagawa, Hajime;Kang, Jaewon;Lee, Giha
    • Journal of the Korean GEO-environmental Society
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    • v.15 no.4
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    • pp.13-27
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    • 2014
  • Catchments soil erosion, one of the most serious problems in the mountainous environment of the world, consists of a complex phenomenon involving the detachment of individual soil particles from the soil mass and their transport, storage and overland flow of rainfall, and infiltration. Sediment size distribution during erosion processes appear to depend on many factors such as rainfall characteristics, vegetation cover, hydraulic flow, soil properties and slope. This study involved laboratory flume experiments carried out under simulated rainfall in a 3.0 m long ${\times}$ 0.8 m wide ${\times}$ 0.7 m deep flume, set at $17^{\circ}$ slope. Five experimental cases, consisting of twelve experiments using three different sediments with two different rainfall conditions, are reported. The experiments consisted of detailed observations of particle size distribution of the out-flow sediment. Sediment water mixture out-flow hydrograph and sediment mass out-flow rate over time, moisture profiles at different points within the soil domain, and seepage outflow were also reported. Moisture profiles, seepage outflow, and movement of overland flow were clearly found to be controlled by water retention function and hydraulic function of the soil. The difference of grain size distribution of original soil bed and the out-flow sediment was found to be insignificant in the cases of uniform sediment used experiments. However, in the cases of non-uniform sediment used experiments the outflow sediment was found to be coarser than the original soil domain. The results indicated that the sediment transport mechanism is the combination of particle segregation, suspension/saltation and rolling along the travel distance.

A Study on Transport Characteristics of MTBE(Methyl Tertiary Butyl Ether) in Soil (MTBE(Methyl Tertiary Butyl Ether)의 토양내 이동특성에 관한 연구)

  • Cho, Ki-Chul;Park, Chang-Woong;Choi, Won-Joon;Kang, Seung-Yub;Hwang, Jong-Hyun;Kim, Youn-Soo;Oh, Kwang-Joong
    • Journal of Korean Society of Environmental Engineers
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    • v.30 no.2
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    • pp.190-198
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    • 2008
  • In this stduy, the column experiments were carried out assuming the soil was contaminated by leakage of gasoline containing MTBE from USTs and pipes around gas stations. Then, characteristics of MTBE transport in the soil were investigated using CXTFIT program. The column experiments with different soil properties, moisture content, organic matter content and flow rate were carried out. Some parameters(D, R, $\beta$, $\omega$) used in two-site non-equilibrium adsorption model were obtained from measuring the MTBE concentration in injection-liquid and in effluent and using CXTFIT program. In addition, The characteristics of MTBE transport in the soil was found using BTCs and obtained parameters. Consequently, the advection decreased as the increase of the content of fine particle and organic, while the MTBE transport by advection was enhanced as increasing flow rate and moisture content.

Mobility of Microplastics in Subsurface Environments: Current Knowledge and Perspectives (지중환경에서 미세플라스틱의 이동성에 대한 고찰)

  • Kim, Youn-Tae;Han, Weon Shik;Yoon, Hye-On
    • Journal of Soil and Groundwater Environment
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    • v.24 no.3
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    • pp.1-12
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    • 2019
  • Plastics have become essential materials in human life for several decades. Meanwhile, the inadvertent spread of plastic debris from the use of many plastic products has raised global environmental concerns. The risk of microplastics in subsurface environment has received little attention because soil is considered to confine microplastics within the matrix. However, the concentration of microplastics in soil unavoidably increased as a result of an increase in plastic production and use. Based on lab experiments, several researches claimed that microplastics possibly penentrate soil layers. Recently, a few researches reported the occurrence of microplastics in groundwater. This study reviewed the recent reports of microplastic occurrences in soil and groundwater, and the modeling studies for simulating transport of microplastics. Additionally, the difficulties and limits in microplastics researches in soil and groundwater are discussed. Finally, several perspectives on microplastic studies in subsurface environment are suggested.