• Geomechanics and Engineering
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• 제14권3호
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• pp.301-306
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• 2018

Stabilization of clayey soil has been studied from past to present by mixing different additives to the soil to increase its strength and durability. In recent years, there has been an increasing interest in stabilization of soils with natural pozzolans. Despite this, very few studies have investigated the impact of pozzolanic additives under freeze-thaw cycling. This paper presents the results of an experimental research study on the durability behavior of clayey soils treated with lime and perlite. For this purpose, soil was stabilized with 6% lime content by weight of dry soil (optimum lime ratio of the the soil), perlite was mixed with it in 0%, 5%, 10%, 20%, 25% and 30% proportions. Test specimens were compacted in the laboratory and cured for 7, 28 and 84 days, after which they were tested for unconfined compression tests. In addition to this, they were subjected to 12 closed system freeze-thaw cycles after curing for 28 days. The results show that the addition of perlite as a pozzolanic additive to lime stabilized soil improves the strength and durability. Unconfined compressive strength increases with increased perlite content. The findings indicate that using natural pozzolan which is cheaper than lime, has positive effect in strength and durability of soils and can result cost reduction of stabilization.

• 한국환경과학회지
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• 제18권2호
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• pp.205-213
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• 2009

A laboratory experiment was conducted to investigate nitrogen removal from plating wastewater by a soil reactor. A combination of soil, waste oyster shell and activated sludge were used as a loading media in a soil reactor. The addition of 20% waste oyster shell and activated sludge to the soil accelerated nitrification (88.6% ${NH_4}^{+}-N$ removal efficiency) and denitrification (84.3% ${NO_3}^{-}-N$ removal) in the soil reactor, respectively. In continuous removal, the influent ${NH_4}^{+}-N$ was mostly converted to nitrate nitrogen in the nitrification soil reactor and only a small amount of ${NH_4}^{+}-N$ was found in the effluent. When methanol was added as a carbon source to the denitrification soil reactor, the average removal efficiency of ${NO_3}^{-}-N$ significantly increased. The ${NO_3}^{-}-N$ removal by methanol addition in the denitrification soil reactor was mainly due to denitrification. The phosphorus was removed by the waste oyster shell media in the nitrification soil reactor. Moreover, the phosphorus removal in the denitrification soil reactor was achieved by synthesis of bacteria and the denitrification under anaerobic conditions. The approximate number of nitrifiers and denitrifiers was $3.3{\times}10^5\;MPN/g$ soil at a depth of $1{\sim}10\;cm$ and $3.3{\times}10^6\;MPN/g$ soil at a depth of $10{\sim}20\;cm$, respectively, in the soil reactor mixed with a waste oyster shell media and activated sludge.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2001년도 추계학술발표회
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• pp.195-198
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• 2001

Bioremediation of hazardous hydrophobic organic compounds, such as polycyclic aromatic hydrocarbons (PAHs), is a major environmental concern due to their toxic and carcinogenic properties. Bue to their low solubility in water, the compounds are microbiologically persistent. This work investigates optimal conditions to enhance the biodegradation of phenanthrene in water and soil-slurry systems. Biodegradation tests were performed with three different types of supplements: glucose as a general carbon source, salicylate as an enzyme inducer, and Triton X-100 as a surfactant. The tests indicate that glucose and Triton X-100 were not very effective to increase biodegradation rate, even though the number of microorganisms are highly increased in the case of glucose addition. Salicylate accelerated biodegradation of phenanthrene, but the addition above optimal concentration inhibited microbial growth. Salicylate is considered to be an attractive alternative for the successful bioremediation of PAH-contaminated soil.

• 한국농공학회논문집
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• 제47권1호
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• pp.43-50
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• 2005

This test was performed to evaluate the change of the unconfined compressive strength, strength parame¡?ters which resulted from direct shear test and oil residue percents analyzed by GC-MS as time lapse, oil addition. Unconfined compression strength of $10\%$ kerosene added by weight of dry soil recovered as time passed. In the case of $5\%$ kerosene added, the strength recovered as much as clean clayey soil after about 50 days passing. For the case of diesel added, the recovery of unconfined compressive strength was not shown even though about 60 days passed. The strength parameters (c, $\psi$) of kerosene added not changed but for diesel added, the cohesion was very decreased as diesel addition increased. Residual percent of kerosene in the soil was less than that of diesel as time passed.

• 자원환경지질
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• 제31권4호
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• pp.291-296
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• 1998

토양 적철석은 오염물질 및 영양분의 흡착과 미세한 입자들의 입단화 매개체로서 잘 알려져 있다. 미세하게 분말화 시킨 결정질 적철석을 두 사질 양토 (Anahuac and Crowley soils from the Southern Coastal Plain, USA)에 첨가하였을 때 나타나는 물리화학적 특성의 변화를 측정하였다. 적철석을 3% (무게비)까지 첨가하였을 때 토양의 투수율이 증가하였으나 그 이상 양을 첨가하였을 때 감소되었다. 토양의 입단안정도 (AS)는 적철석 첨가에 영향을 받지않았다. 같은 양의 적철석을 Anahuac soil과 Crolwey soil에 첨가하였을 때 높은 유기물의 함량과 낮은 Na 흡착비 (SAR: sodium adsorption ratio)를 가진 Anahuac soil은 Crowley soil에 비해 상대적으로 높은 투수율과 입단안정도를 보여주었다. 두 토양 모두 Zn 흡착은 약간 증가하였으나 인산염 흡착은 영향을 받지않았다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제13권3호
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• pp.59-66
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• 2008

본 연구는 유류화합물로 오염된 토양의 생물학적 정화효율을 향상시키기 위한 연구로서, 정화목표인 TPH 500 mg/kg을 달성하기 위하여 유기성 영양분과 화학적 산화를 추가적으로 연계 적용하여 생물학적 정화효율의 성능향상 시험을 수행하였다. 경유로 오염된 토양을 대상으로 시험한 결과, 생물학적으로 정화하는 과정에서 무기성 성분(N, P)을 영양분으로 사용하여 정화한 경우에서 보다(정화효율 80.2%) 유기성 영향분인 퇴비와 액분을 사용한 경우가 각각 84.4%, 92.2%로 높은 정화효율을 보여주었다. 난분해성 물질을 함유한 토양의 생물학적 정화과정에서 tailing 현상이 일어나는 기간에 화학적 산화와 생물학적 정화를 병행하였을 때 TPH 농도를 134 mg/kg로 떨어뜨려 정화효율 98.1%를 얻은 반면에 생물학적 정화만 진행한 경우 TPH 1,073 mg/kg로 정화효율 84.7%를 나타내 화학적 산화의 병행처리가 더 효과적임을 알 수 있었다.

• 한국토양비료학회지
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• 제48권6호
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• pp.634-640
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• 2015

Chelating agents have been proposed to improve the efficiency of phytoextraction of heavy metal hyperaccumulator. However, little studies to elucidate mechanism of chelating agents to increase cadmium (Cd) extractability have been conducted. The objectives of this study were to evaluate effect of different chelating agents on Cd extractability and to determine mechanism of Cd mobilization affected by these agents. An arable soil was spiked with inorganic Cd ($CdCl_2$) to give a total Cd concentration of $20mgCdkg^{-1}$. Ethylenediaminetetraacetic acid (EDTA) and citric acid (CA) were selected and mixed with the arable soil at the rates of 0 and $5mmolkg^{-1}$. The mixture soils were incubated at $25^{\circ}C$ for 4 weeks in dark condition. Concentration of F1 Cd fractions (water soluble) significantly increased with addition of EDTA but did not changed with addition of CA. Especially; concentration of F5 Cd fractions (residual) significantly increased with addition of CA. Increase in water soluble with EDTA might be attributed to complexation of Cd and EDTA. Dissolved organic carbon concentration significantly increased with EDTA addition, but did not with CA implying that considerable amount of CA was decomposed to inorganic carbon by microorganism. Log activity of carbonate ($CO_3{^{2-}}$) which might be generated from CA increased with addition of CA. Increase in residual Cd fraction might be due to precipitation of Cd as $CdCO_3$. As a result, EDTA was effective in increasing Cd extractability, by contrast CA had significant effect in reducing Cd extractability.

• 한국환경보건학회지
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• 제23권4호
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• pp.97-103
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• 1997

Carbofuran was incubated for four weeks in three differenf types of paddy soil samples at 25$\circ$C. The soil samples prepared in the present study were as follows: control soil, 3% cellulose added soil and 10% cellulose added soil. The degradation rate of carbofuran significantly decreased by the addition of cellulose to soil(p<0.05). The initial pH of soils was 5.0. After incubation for four weeks, the pH of 10% cellulose added soil sample was lower than those of control soil and 3% cellulose added soil. According to increased organic carbon content of the soil, redox potentials of soils decreased. The decreased degradation rate of carbofuran in 10% cellulose added soil was related to the highly negative redox potentials in contrast with the oxidised conditions of control soil and 3% cellulose added soil.

• 한국지하수토양환경학회지:지하수토양환경
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• 제18권7호
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• pp.63-72
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• 2013

This study estimated stabilization efficiency of As and heavy metal contaminated agricultural soil in abandoned mine through pot experiment. Also contaminants uptake of plant (lettuce) was compared as function of amendment (limestone, steelmaking slag and the mixture of these) addition. In soil solution analysis, concentration of contaminants in soil solutions which added limestone or steelmaking slag were lower than that of the mixture. Especially in As analysis, concentration with 5% (wt) addition of steelmaking slag showed the lowest value among those with other amendments. This seems that As stabilization happens through Fe adsorption during precipitation of Fe by pH increasing. Leachability of As in stabilized soil by TCLP was represented similar result with soil solution analysis. However leachability of heavy metals in stabilized soil was similar with that of non-stabilized soil due to dissolution of alkali precipitant by weak acid. Contaminants uptake rate by plant was also lower when limestone or steelmaking slag was used. However this study revealed that concentration of contaminants in soil solution didn't affect to the uptake rate of plant directly. Because lower $R^2$ (coefficient of determination) was represented in linear regression analysis between soil solution and plant.

• 한국의류학회지
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• 제23권7호
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• pp.1030-1039
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• 1999

The effect of surfactant mixture 9on detergency and soil redeposition in a dry-cleaning system was investigated employing Aerosol OT as an anionic surfactant and Span 80 as a nonionic surfactant. The effect of charge system on soil deposition was also investigated in order to determine the optimum condition at which soil redeposition is minimum,. Soil deposition instead of soil redeposition on cotton, polyester and wool fabrics was measured employing petroleum solvent and perchloroethylene as organic solvents. The results were as follows. 1. Surface tension or interfacial tension was not changed by the addition of any surfactant or surfactant mixtures. In petroleum solvent however interfacial tension between solrent and water decreased when surfactants were added and increased when surfactants were mixed,. 2. The maximum amount of water solubilization increased as the mole fraction of Aerosol OT increased and more water was solubilized in petroleum solvent than in perchloroethylene. 3. The detergency of cotton was greater and the soil deposition rate was lower in Span 80 solution than in Aerosol OT solution. The soil deposition on cotton fabric decreased when water was solubilized in Aersol OT solution 4. The detergency and soil deposition rate of polyester fabric did not change by the surfactant type of the addition of surfactant mixture and soil deposition rate increased bywater solubilization. 5. Soil deposition on wool fabric was very high when Arosol OT was employed in perchloroethylene and the soil deposition did not change greatly by water solubilization.