• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2004.04a
• /
• pp.19-22
• /
• 2004

Two-dimensional modeling studies using TOUGHREACT were conducted to investigate the coupling between flow and transport developed as a consequence of differences in density, dissolution/ precipitation, and medium heterogeneity. The model includes equilibrium reactions for aqueous species, kinetic reactions between tile solid phases and aqueous constituents, and full coupling of porosity and permeability changes resulting from precipitation and dissolution reactions in porous media. Generally, the evolutions in the concentrations of the aqueous phase are intimately related to the reaction-front dynamics. Plugging of the medium contributed to significant transients in patterns of flow and mass transport.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2002.04a
• /
• pp.18-21
• /
• 2002

Phytoremediation which uses plants to enhance the bioremediation through stimulation of microbial activity and root uptake, has been a topic of increasing interest. Mathematical model were developed that can be applied to various bioremediation methods in the unsaturated zone, especially phytoremediation, for simulating the fate and transport of contaminants under field conditions. A 2-year field study was conducted using 72 (1.5m long and 0.1 m diameter) column lysimeters with four treatments: Johnsongrass; wild rye grass; a rotation of Johnsongrass and wild rye grass; and unplanted fallow conditions. The developed model represented the fate and transport of contaminant both in vegetated and unplanted soils satisfactorily for field applications. Parameters related to the contaminant concentration in the water phase were the main parameters determining the contaminant fate in the vadose zone and indicated that the bioavailability can be the most important factor in the success of phytoremediation as well as bioremediation applications.

• Journal of Soil and Groundwater Environment
• /
• v.24 no.3
• /
• pp.13-23
• /
• 2019

The purpose of this study is to suggest conceptual models based on finite numerical method that can be used to assess contaminant transport through subsurface and estimate exposed concentration at contaminated site. This study tested various assumptions of the numerical models for contaminant transport in unsaturated and saturated zones to simulate the pathways to the human exposal point. For this purpose, models for seven possible scenarios of contaminant transport were simulated using the numerical code MODFLOW and MT3D. The simulation results that showed different peak concentrations and travel times were compared. In conclusion, the potential utility of the numerical models in the site specific risk analysis suggested as well as future research ramifications.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2001.04a
• /
• pp.128-131
• /
• 2001

We evaluated natural attenuation of petroleum hydrocarbons in a shallow aquifer using a modeling study. The studied shallow aquifer was severely contaminated with petroleum hydrocarbons, especially toluene, ethylbenzene and xylenes (i.e, TEX). The exact spill history was not known. Therefor we used a contaminant level in May 1999 (the first sampling date of our integrated study) as an initial contaminant concentration. we calibrated required transport parameters using the contamination levels obtained from groundwater analyses in September of 1999. For fate and transport of the petroleum contaminants, five case 2 with sorption and degradation. case 3 with sorption and degradation (half decay constant compared with case 2), case 4 with degradation but no sorption, and case 5 with sorption but no degradation. For sorption and degradation, a linear sorption isotherm and first order irreversible decay was assumed, respectively and no additional contamination source to groundwater is also assumed.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2003.04a
• /
• pp.111-114
• /
• 2003

A new monitoring system has been developed for in-situ and realtime measurement of ozone transport in unsaturated porous media using a fiber optic sensor. The calibration of the fiber optic transflection dip probe (FOTDP) system was successfully carried out at various ozone concentrations using a column with length of 30 cm and diameter of 5 cm packed with glass beads, which don't react with gaseous ozone. The breakthrough curves (BTCs) of ozone was obtained by converting the normalized intensity into ozone concentration. The FOTDP system reflected the ideal transport phenomena of gas phase ozone at various flow rates. The FOTDP system worked well for in-situ monitoring of gas phase ozone at various water saturations and in presence of SOM. However, the FOTDP system did not measure the ozone concentration at more than 70% water saturation.

• Journal of Soil and Groundwater Environment
• /
• v.25 no.1
• /
• pp.37-52
• /
• 2020

Sensitivity analysis of hydrodynamic and reaction parameters in conceptual model reflecting aquifer characteristics of Korea was performed to evaluate the uncertainty in the predicted concentrations. Among the hydrodynamic input parameters, both hydraulic conductivity (K_x) and hydraulic gradient (I) affected transport behaviors of contaminants, and resulted in same convergence concentrations with continuous injections of contaminant. However, longitudinal dispervisity (α_L) affected both transport behaviors and the convergence concentrations of contaminants. Compared to the hydrodynamic parameters, growth kinetic and degradation parameters (μ_m & K_c) more significantly affected both transport behaviors and the convergence concentrations of contaminants, indicating those parameters had higher sensitivity indices causing the uncertainties of model predictions. Considering that the sensitivity indices of both hydrodynamic and reaction parameters were a function of transport distance of groundwater, the parameters with higher sensitivity indices, a priori, need to be investigated using conceptual model reflecting site-specific aquifer characteristics before field investigation. After determining the parameters with higher sensitivity indices, the detail field investigations for the selected hydrodynamic and reaction parameters were warranted to reduce the uncertainties of model predictions.

• Environmental Engineering Research
• /
• v.24 no.3
• /
• pp.456-462
• /
• 2019

Hydrocarbon contamination is among the most challenging problems in soil remediation. Electrokinetic method can be a promising method to remediate hydrocarbon-contaminated soils. Electrokinetic method consists of different transport phenomena including electro-migration, electrophoresis, and electroosmotic flow. Electroosmotic flow is the main transport phenomenon for hydrocarbon removal in soil porous media. However, the main component of hydrocarbons is the hydrophobic organic which indicates low water solubility; therefore, it makes the electroosmotic flow less effective. The objective of the present study is to enhance electrokinetic remediation of diesel-contaminated silty sand by increasing the solubility of the hydrocarbons in the soil and then increase the efficiency. For this purpose, sodium dodecyl sulfate (SDS) was used as a catholyte. In this content, SDS 0.05 M was used as catholyte and $Na_2SO_4$ 0.1 M was used as an anolyte. Low (1 V/cm) and high (2 V/cm) voltage gradients were used in periodic and continuous forms. The best removal efficiency was observed for high voltage gradient (2 V/cm) in a periodic form, which was 63.86. This result showed that a combination of periodic voltage application in addition to the employment of SDS is an effective method for hydrocarbon removal from low permeable sand.

• Coupled systems mechanics
• /
• v.3 no.1
• /
• pp.27-52
• /
• 2014

For landfill monitoring and aftercare, long-term prognoses of emission and deformation behaviour are required. Landfills may be considered as heterogeneous porous soil-like structures, in which flow and transport processes of gases and liquids interact with local material degradation and mechanical deformation of the solid skeleton. Therefore, in the framework of continuous porous media mechanics a model is developed that permits the investigation of coupled mechanical, hydraulical and biochemical processes in municipal solid waste landfills.

• Korean Journal of Soil Science and Fertilizer
• /
• v.39 no.1
• /
• pp.29-37
• /
• 2006

In remediation of the contaminated soil, it requires to select at least more than two remediation technologies depending on the fate and transport phenomena through complicated reactions in soil matrix. Therefore, methodologies related to develop the integrated remediation technology were reviewed for agricultural soils contaminated with heavy metals. Pneumatic fracturing is necessary to implement deficiency because soil washing is not effective to remove heavy metals in the subsurface soil. But it needs to evaluate the characteristics such as essential data and factors of designated technology in order to effectively apply them in the site. In the remediation site, the important soil physical and chemical factors to be considered are hydrology, porosity, soil texture and structure, types and concentrations of the contaminants, and fate and its transport properties. However, the integrated technology can be restrictive by advective flux in the area which remediation is highly effective although both soil washing and pneumatic fracturing were applied simultaneously in the site. Therefore, we need to understand flow pathways of the target contaminants in the subsurface soils, that includes kinetic desorption and flux, predictive simulation modeling, and complicated reaction in heterogenous soil.

• Journal of Korea Soil Environment Society
• /
• v.3 no.3
• /
• pp.3-10
• /
• 1998

Acid/Base buffer capacity of soil is very important in prediction of contaminant transport for its direct impact on pH change of the system composed of soil-contaminant-water, In this research, diffuse double layer theory as well as two layer electrostatic adsorption model are applied to develop a theoretical model of buffer capacity of soil. Model application procedures are presented as well. Buffer capacity of Georgia kaolinite and Milwhite kaolinite was measured by acid-base titration. Model prediction and experimental results are compared.