• KSBB Journal
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• v.28 no.5
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• pp.275-281
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• 2013

Soil microbial community analysis of farmland soil sprayed with lye in order to use fertilizer in Nigeria was performed. As a control, two kinds of soils not sprayed with lye, located in Eungo and Lagos with general practice in agriculture was selected. Soil sprayed with lye was pH 8.25 through alkalization reaction, while the other soil samples were pH 6.22 and 5.94. Substrate utilization and species diversity index of soil sprayed with lye were low than that of the other soils with the analysis of Biolog ecoplate. As a result of principal component analysis, the relationship between three samples was low. Microbial community analysis was performed by DGGE and most of them were soil uncultured bacterium. Especially, Uncultured Acidobacteria and Uncultured Methylocystis sp., which had been isolated from the rhizosphere of soybean grown in that site were discovered in the soil sprayed with lye.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.83-86
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• 2003

Soil Aquifer Treatment (SAT) is a technique in which secondary- or tertiary-treated wastewater is infiltrated through unsaturated soil and stored in the saturated zone. In SAT, contaminants are removed by physical and biochemical reactions taking place in soils. In this study, a numerical model was developed to predict changes in water quality during SAT operations. The contaminant species considered in the model were ammonium, nitrate, dissolved organic carbon, and dissolved oxygen. The model was calibrated against experimental data obtained from one dimensional soil column tests conducted for 84 days. The calibrated model will be used to find out optimum conditions for the pilot- and regional-scale SAT operations to be scheduled for the next phase of this project.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2000.05a
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• pp.145-148
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• 2000

• Journal of the Earthquake Engineering Society of Korea
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• v.27 no.1
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• pp.25-35
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• 2023

Considering the non-linear behavior of structure and soil when evaluating a nuclear power plant's seismic safety under a beyond-design basis earthquake is essential. In order to obtain the nonlinear response of a nuclear power plant structure, a time-domain SSI analysis method that considers the nonlinearity of soil and structure and the nonlinear Soil-Structure Interaction (SSI) effect is necessary. The Boundary Reaction Method (BRM) is a time-domain SSI analysis method. The BRM can be applied effectively with a Perfectly Matched Layer (PML), which is an effective energy absorbing boundary condition. The BRM has a characteristic that the magnitude of the response in far-field soil increases as the boundary interface of the effective seismic load moves outward. In addition, the PML has poor absorption performance of low-frequency waves. For this reason, the accuracy of the low-frequency response may be degraded when analyzing the combination of the BRM and the PML. In this study, the accuracy of the analysis response was improved by adjusting the PML input parameters to improve this problem. The accuracy of the response was evaluated by using the analysis response using KIESSI-3D, a frequency domain SSI analysis program, as a reference solution. As a result of the analysis applying the optimal PML parameter, the average error rate of the acceleration response spectrum for 9 degrees of freedom of the structure was 3.40%, which was highly similar to the reference result. In addition, time-domain nonlinear SSI analysis was performed with the soil's nonlinearity to show this study's applicability. As a result of nonlinear SSI analysis, plastic deformation was concentrated in the soil around the foundation. The analysis results found that the analysis method combining BRM and PML can be effectively applied to the seismic response analysis of nuclear power plant structures.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.5
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• pp.352-357
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• 2009

Due to rapid consumption of hydrogen peroxide, large amount of hydrogen peroxide is required when Fenton reaction is applied to the contaminated soil. In this study, acetate was employed as a ligand of $Fe^{2+}$ to enhance the efficiency of removal of phenanthrene by securing the stability of hydrogen peroxide. 0.5 ${\sim}$ 3 times of acetate (2${\sim}$12mM) was added to compare with molar concentration of $Fe^{2+}$. Low initial concentration of hydrogen peroxide was 0.7% to eliminate side effect of removal efficiency. The results showed that hydrogen peroxide lifetime was lasted up to 72 hours, or more than 50 times of normal lifetime. Phenanthrene removal efficiency was improved up to 70% due to stabilized hydrogen peroxide. Ferrous ion was oxidized to ferric ion and oxidation-reduction was repeated during the reaction. Finally ferric ion was reduced to ferrous by $HO_2$. It was confirmed that, due to the influence of hydrogen peroxide, pH was acid region and it remained at the range of 4 ${\sim}$ 5 when 8 mM or more of acetate was added. Acetate which was used as the ligand of Fe was also decomposed by Fenton reaction. The decomposition time of acetate was slower than phenanthrene. Therefore, it was able to come to the conclusion that phenanthrene was superior to acetate at the competition for decomposition. Through the results of this study, it was able to identify the possibilities to improve the efficiency of Fenton reaction in the contaminated soil and its economic feasibility, and to move to more realistic technique through research expanded to neutral pH region.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.2
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• pp.95-102
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• 2014

In this paper, a coupling scheme for applying finite element analysis(FEA) programs, such as, LS-DYNA and MIDAS/Civil, to a nonlinear soil structure interaction analysis by the boundary reaction method(BRM) is presented. With the FEA programs, the structure and soil media are discretized by linear or nonlinear finite elements. To absorb the outgoing elastic waves to unbounded soil region as much as possible, the PML elements and viscous-spring elements are used at the outer FE boundary, in the LS-DYNA model and in MIDAS/Civil model, respectively. It is also assumed that all the nonlinear elements in the problem are limited to structural region. In this study, the boundary reaction forces for the use in the BRM are calculated using the KIESSI-3D program by solving soil-foundation interaction problem subjected to incident seismic waves. The effectiveness of the proposed approach is demonstrated with a linear SSI seismic analysis problem by comparing the BRM solution with the conventional SSI solution. Numerical comparison indicates that the BRM can effectively be applied to a nonlinear soil-structure analysis if motions at the foundation obtained by the BRM for a linear SSI problem excluding the nonlinear structure is conservative.

• Journal of Environmental Science International
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• v.17 no.1
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• pp.97-105
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• 2008

This study examined the contaminated soils with an indicator of TPH using SVE (Soil Vapor Extraction) and biological treatments. Their results are as follows. Water content in the polluted soils slowly decreased from 15% during the initial experimental condition to 10% during the final condition. Purification of polluted soils by Bioventing system is likely to hinder the microbial activity due to decrease of water content. Removal rate of TPH in the upper reaction chamber was a half of initial removal rate at the 25th day of the experiment. The removal rate in the lower reaction chamber was 45% with concentration of 995.4 mg/kg. When the Bioventing is used the removal rate at the 14th day of the experiment was 53%, showing 7 day shortenting. Since the Bioventing method control the microbial activity due to dewatering of the polluted soil, SVE method is likely to be preferable to remove in-situ TPH. The reactor that included microbes and nutrients showed somewhat higher removal rate of TPH than the reactor that included nurtients only during experimental period. In general, the concentration showed two times peaks and then decreased, followed by slight variation of the concentration in low concentration levels. Hence, in contrast to SVE treatment, the biological treatment tend to show continuous repetitive peaks of concentration followed by concentration decrease.

• Journal of Environmental Science International
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• v.9 no.5
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• pp.437-441
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• 2000

A study on the removal of Pb ion from Pb-contaminated soil was carried out using ex-site extraction process. Tartaric acid (TA) and iminodiacetic acid sodium salt(IDA) as a washing agent were evaluated as a function of concentration reaction time mixing ratio of washing agent and recycling of washing agent. TA showed a better extraction performance than IDA. The optimum washing condition of TA and IDA were in the ratio of 1:15 and 1:20 between soil and acid solution during 1 hr reaction. The total concentrations of Pb ion by TA and IDA at three repeated extraction were 368.8 ppm and 267.5 ppm respectively. The recovery of Pb ion from washing solution was achieved by adding calcium hydroxide and sodium sulfide form the precipitation of lead hydroxide and lead sulfide and optimum amounts of sodium sulfide and calcium hydroxide were 7 g/$\ell$ for the TA washing solution and 4 g/$\ell$, 5g/$\ell$ for the IDA washing solution respectively. The efficiency of recycle for TA and IDA washing solution were 78.8% , 95.1%, and 89.2%, 96.6% at third extractions under $Na_2S$ and $Ca(OH)_2$, respectively.

• Journal of Soil and Groundwater Environment
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• v.21 no.4
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• pp.50-59
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• 2016

Spatial and temporal changes in nitrification activities and distribution of microbial population of ammonia oxidizing bacteria (AOB) and ammonia oxidizing archaea (AOA) in paddy soils were investigated. Soil samples were collected in March and October 2015 from rice paddy with and without the presence of confined animal feeding operations. Incubation experiments and quantitative polymerase chain reaction showed that AOA's contribution to nitrification kinetics was much higher in locations where organic nitrogen in animal waste is expected to significantly contribute to overall nitrogen budget, and temporal variations in nitrification kinetics were much smaller for AOA than AOB. These differences were interpreted to indicate that different microbial responses of two microbial populations to the types and concentrations of nitrogen substrates were the main determining factors of nitrification processes in the paddy soils. The copy numbers of ammonium monooxygenase gene showed that AOA colonized the paddy soils in higher numbers than AOB with stable distribution while AOB showed variation especially in March. Although small in numbers, AOB population turned out to exert more influence on nitrification potential than AOA, which was attributed to higher fluctuation in AOB cell numbers and nitrification reaction rate per cells.

• Structural Engineering and Mechanics
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• v.59 no.4
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• pp.739-759
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• 2016

The failure of civil engineering systems is a consequence of decision making under uncertain conditions. Generally, buried flexible pipes are designed for their transversal behavior to prevent from the important failure mode of buckling. However, the interaction effects between soil and pipe are neglected and the uncertainties in their properties are usually not considered in pipe design. In this regard, the present research paper evaluates the effects of these uncertainties on the uncertainty of the critical buckling hoop force of flexible pipes shallowly buried using the subgrade reaction theory (Winkler model) and First-Order Second-Moment (FOSM) method. The results show that the structural uncertainties of the studied pipes and those of the soil properties have a significant effect on the uncertainty of the critical buckling hoop force, and therefore taking into account these latter in the design of the shallowly flexible pipes for their buckling behavior is required.