• Journal of Soil and Groundwater Environment
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• v.6 no.2
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• pp.23-30
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• 2001

Column tests were carried out to examine the effect of surfactant solution conditions on the surfactant-enhanced remediation of soil columns contaminated by toluene. The conditioned parameters of the surfactant solution for the column tests were concentration, pH, temperature and flow rate. The test results revealed that an optimum condition was achieved for 4% (v/v) of concentration, 10 of pH, $20^{\circ}C$ of temperature and 4 mL/min of flow rate respectively. The removal of 95% of toluene was obtained when optimal conditions of each surfactant solution parameter were simultaneously met. This was a marked improvement and removal efficiency increased by 6-19% compared to that with unadjusted conditions. The optimum range of these parameters may be useful for a surfactant-based remediation in the aquifer contaminated by toluene.

• Journal of Soil and Groundwater Environment
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• v.12 no.2
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• pp.47-54
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• 2007

The partitioning tracer method has been studied as an alternative method for detecting and characterizing the distribution of nonaqueous phase liquids (NAPLs) contaminants in subsurface. The reliability of the partitioning tracer method depends on accurate measurements of partition coefficients of the partitioning tracers between water and NAPLs. In this study, partition coefficients of several alcohol tracers between water and benzene, toluene, ethylbenzene, xylene, and BTEX mixtures are estimated using the modified approach of equivalent alkane carbon number (EACN). Agreements between the measured and estimated partition coefficients were generally observed in experiments. Based on these results, it is confirmed that the partition coefficients of tracers are readily obtained without experiments if the EACN values for the tracers and LNAPLs are known.

• Economic and Environmental Geology
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• v.34 no.4
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• pp.417-422
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• 2001

Sutfactants may be used in remediation of subsoil and aquifer contaminated with hydrophobic compounds. The objectives of this study were to select potentially suitable sUlfactants that solubilize toluene present as a contaminant and to determine the effectiveness of toluene removal from Ottawa sand by the selected surfactants. Material used as the model soil was Ottawa sand and the organic used as model contaminant was toluene. Used experimental methods were separatory funnel experiment and shaker table agitation/centrifugation experiments. Based on the experimental results, the following conclusions were drawn; t) In the surfactant selection, six different surfactants were chosen based on surfactant types, toxicity, and water solubility. These six were focused into two on the basis of HLB and surface tension study, separatory funnel experiment, shaker table and centrifugation experiments. The two most suitable surfactants were Sandopan JA36 (an anionic surfactant), and Pluronic L44 (a non-ionic surfactant). 2) In the shaker table agitation and centrifugation experiments, the highest recovery of the toluene was 96% which was obtained with one surfactant wash plus two water rinses using an anionic surfactant (Sandopan JA36).

• The Journal of Engineering Geology
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• v.8 no.1
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• pp.51-73
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• 1998

Hydrogeological systems in a metrnpolitan area can be understood by analyzing the groundwater disturbing factors such as constructions and land applications, the groundwater usage for domestic and industrial purposes, and the groundwater pumpage to lower the groundwater level for the structural safety of subway and underground facilities. This study is part of the study performed to understand the groundwater system in the Seoul area and it is focusing on the hydraulic properties. Groundwater well inventory, barometric efficiency measurements, pumping and slug tests, and long-term groundwater monitoring have been perfonrmed during the last 2 years. The relations between Han River and the groundwater around the river also have been observed. These observations and test data, together with the information on soil distribution, geology, and logging data are used to construct a database and GIS(Geographic Information System) presentation system using ARC/INFO. Barometric efficiencies appeared to have no special trends associated with well depths, which maeans that the degree of confinement of the crystaline rock aquifer of the Seoul area is distributed locally depending on the developrnent of fractures. Hydraulic conductivities exponentialiy decrease with well depth. The stage of Han River fluctuates according to the tidal movement of nearby seawater but the tidal effects attenuate due to the underwater dams. Groundwater levels in the Seoul area seem to have declined for the last two years,but it is not certain that the declination represents the long-term trend.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.6
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• pp.1113-1126
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• 2000

Humic substances present in landfill leachates were extracted and their characteristics were analyzed with respect to landfilling age as a basic study to evaluate the effect of humic substances on the transport and transformation of other pollutants in pollution plume contaminated by landfill leachate. Element analysis of the extracted humic substances were performed. The information on the functional groups of the humic substances molecules were obtained from the spectroscopic analysis using UV-visible, FT/IR, and fluorescence spectroscopy. The structural characteristics of the humic substances were also analyzed by $^1H$ and $^{13}C$ NMR spectroscopy. From the results of the analyses it was found that the structure of the humic substances present in landfill leachates was more aliphatic than aromatic relative to other common humic substances extracted from natural soils and water. The results indicate that the degree of humification of the humic substances were relatively low. The degree of humification, however, was increased as the landfilling age was increased.

• Economic and Environmental Geology
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• v.41 no.4
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• pp.393-403
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• 2008

Hydrogeochemistry of groundwater was studied in order to identify the influence of cow manure, distributed to a farmland as organic fertilizer, on nitrate concentrations in shallow groundwater and its spatio-temporal variations. From monitoring wells, water levels were measured using automatic data loggers, and water samples collected and analyzed in Feb., April, June and Oct. 2007. The average electric conductivity and concentration of nitrate in the groundwater show the highest levels in April and decline in subsequent sampling times. Decreases in dissolved oxygen(DO) and nitrate concentrations from April to Oct. and corresponding increases in $HCO_3$ concentrations indicate denitrification processes by microorganisms. Spatial variation of nitrate concentration appeared to be affected by the redox conditions of groundwater controlled by geochemical reactions of Mn, Fe and DOC contents.

• Water for future
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• v.16 no.4
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• pp.245-252
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• 1983

Recently river water pollution in Korea is given rise to serious problem in aspect of crop production, drinking well, water contamination and etc. Under these urgent situations, it is prime importance to protect water resources from pollutants. An environmental isotope survey of the groundwater form the shallow alluvial and the underlying crystalline rock aquifer of the Han River Basin has been undertaken, Analysis of the data has I) confirmed the hypothesis that the groundwater from the metropolitan area is recharged from the river whereas that form the non-urbanized region of the Basin is replenished by the infiltrating precipitation; ii) shown that crystalline rock aquifers are recharged by the ground water form the overlying alluvium. Old groundwater is a group of wells with tritium values in the range of 0 to 2 TU. These low values indicate that the water sampled was recharged much ealier, at least a few decades, than the other groundwater samples of higher tritium content. The low values in this region may, in fact, reflect the effect of the impermeable clay layers which impede infilteration from the surface. Stable isotope evidence confirmed that a recharge in the karst area occurs at a significantly greater elevation than that to the alluvial aquifer. An analysis of the tritium level collected over an annual cycle suggests that the residence time of groundwater is probably not more than a few months. There does not appear to be any correlation between the trace level of Zn, Mn and Pb in the groundwater and the mechanism of the recharge.

• Water for future
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• v.29 no.5
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• pp.215-222
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• 1996

An expression for the cross covariance of the logconductivity and the head in nonstationary porous formation is obtained. This cross covariance plays a key role in the inverse problem, i.e., in inferring the statistical characteristics of the conductivity field from head data. The nonstationary logconductivity is modeled as superposition of definite linear trend and stationary fluctuation and the hydraulic head in saturated aquifers is found through stochastic analysis of a steady, two-dimensional flow. The cross covariance with a Gaussian correlation function is investigated for two particular cases where the trend is either parallel or normal to the head gradient. The results show that cross covariances are stationary except along separation distances parallel to the mean flow direction for the case where the trend is parallel to head gradient. Also, unlike the stationary model, the cross covariance along distances normal to flow direction is non-zero. From these observations we conclude that when a trend in the conductivity field is suspected, this information must be incorporated in the analysis of groundwater flow and solute transjport.

• Journal of Korean Society of Water and Wastewater
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• v.13 no.4
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• pp.62-71
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• 1999

The containment retardation capacities of four different aquifers were evaluated in a preliminary study for development of bank filtration in the Young San river area. $NO_3-N$, $NO_2-N$, $NH_4^+-N$, Fe, Mn, phenol, and chloride were selected as the target contaminants and a nonreactive tracer, respectively. Batch isotherm tests were conducted to measure the partition coefficients of the target contaminants. The mass transport parameters of nonreactive tracer were estimated from column tests. From the results of bath isotherm tests, it was shown that lower stream aquifer materials have greater partition coefficients of $NO_3-N$, $NH_4^+-N$, Mn, and phenol than the upper stream aquifer materials; however, there was no significant position-dependent trend for Fe. All aquifer materials tested have the same range of partition coefficients for $NO_2-N$. Column tests showed that the molecular diffusion of Cl- was much less than the mechanical dispersion; and there was no significant difference between the estimated dispersivities of tested aquifer materials. Consequently, it seems that the difference in the containment retardation capacities between four aquifers tested in this study would primarily result not from hydrodynamic dispersion but from partitioning.

• Journal of the Korean Society of Groundwater Environment
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• v.7 no.1
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• pp.8-14
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• 2000

The present day, interest in low flow statistics has been increased, primarily because of the increase in water demands and the contamination of water quality and the limitation of water resource development and the annual water supply stability. The model for estimating low flow statistics is points of this study chosen catchments in the Youngsan basin. For the purpose of this study. the low-flow discharge at 23 points, where absent gauging station is unmeasured and the data is used for the model. Finally, the regional formula to estimate the low flow statistics at the unmeasured point is proposed.