• Title/Summary/Keyword: Environmental contaminants

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Bioavailability of slow-desorbable naphthalene in a biological air sparging system

  • Li, Guang-Chun;Chung, Seon-Yong;Park, Jeong-Hun
    • Advances in environmental research
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    • v.1 no.3
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    • pp.201-210
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    • 2012
  • The bioavailability of sorbed organic contaminants is one of the most important factors used to determine their fate in the environment. This study was conducted to evaluate the bioavailability of slow-desorbable naphthalene in soils. An air sparging system was utilized to remove dissolved (or desorbed) naphthalene continuously and to limit the bacterial utilization of dissolved naphthalene. A biological air sparging system (air sparging system with bacteria) was developed to evaluate the bioavailability of the slow-desorption fraction in soils. Three different strains (Pseudomonas putida G7, Pseudomonas sp. CZ6 and Burkholderia sp. KM1) and two soils were used. Slow-desorbable naphthalene continuously decreased under air sparging; however, a greater decrease was observed in response to the biological air sparging system. Enhanced bioavailability was not observed in the Jangseong soil. Overall, the results of this study suggests that the removal rate of slow-desorbable contaminants may be enhanced by inoculation of degrading bacteria into an air sparging system during the remediation of contaminated soils. However, the enhanced bioavailability was found to depend more on the soil properties than the bacterial characteristics.

A Tiered Approach of Washing and Stabilization to Decontaminate and Recycle Dredged River Sediment (세척과 안정화기술을 적용한 오염 준설토의 처리 및 재활용 시스템 개발)

  • Kim, Young-Jin;Nam, Kyoung-Phile;Lee, Seung-Bae;Kim, Byeong-Kyu;Kwon, Young-Ho;Hwang, In-Seong
    • Journal of Soil and Groundwater Environment
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    • v.15 no.2
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    • pp.47-54
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    • 2010
  • Although the demands for the dredging work have been increasing due to social and industrial reasons including national plan for restoration of four major rivers, environmental standards or management guidelines for the dredged river sediment are limited. The suggested environmental standard for the beneficial use of dredged river sediment consists of two levels, recyclable and concern, and includes eight contaminants such as metals and organic contaminants. The systematic approach to remediate dredged river sediment is also suggested. The system consists of both washing and stabilization processes with continuous multi particle separation. In the early stage, the sediments are separated into two particle sizes. The coarse-grained sediment over 0.075 mm, generally decontaminated with less trouble, follows normal washing steps and is sent for recycling. The fine-grained sediments under 0.075 mm are separated again at 0.025 mm. The particles bigger than this second separation point are treated in two ways, advanced washing for highly contaminated sediments and stabilization for less. The lab test results show that birnessite and apatite are most effective stabilizing agents among tested for Cd and Pb. The most fine residues, down-sized by continuous particle separation, are finally sent for disposal. The system is tested for metals in this study, but is expected to be effective for organic contaminants included in the environmental standard, such as PAH and PCE. The feasibility test on the field site will be followed.

Development of the Two-Zone Model to Estimate the Air Quality in Indoor Environments (실내 공기질 평가를 위한 2구획 모델의 개발)

  • 조석호;양성환;이봉헌;정성욱;이병호
    • Journal of Environmental Science International
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    • v.7 no.6
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    • pp.745-751
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    • 1998
  • The well-mixed room model has been traditionally used to predict the concentrations of contaminants in indoor environments. However, this is inappropriate because the flow fields in many indoor environments distribute contaminants non-uniformly, due to imperfect air mixing. Thus, some means used to describe an imperfectly mixed room are needed. The simplest model that accounts for imperfect air mixing is a two-zone model. Therefore, this study on development of computer program far the two-zone model is carried out to propose techniques of estimating the concentration of contaminants in the room. To do this, an important consideration is to divide a room into two-zone, i.e. the lower and upper zone assuming that the air and contaminants are well mixed within each zone. And between the zones the air recirculation is characterized through the air exchange parameter. By this basic assumption, the equations for the conservation of mass are derived for each zone. These equations are solved by using the computational technique. The language used to develope the program is a VISUAL BASIC. The value of air exchange coefficient($f_12$) is the most difficult to forecast when the concentrations of contaminants in an imperfectly mixed room are estimated by the two-zone model. But, as the value of $f_12$ increases, the air exchange between each zone increases. When the value of $f_12$ is approximately 15, the concentrations in both zone approach each other, and the entire room may be approximately treated as a single well-mixed room. Therefore, this study is available for designing of the ventilation to improve the air quality of indoor environments. Also, the two-zone model produces the theoretical base which may be extended to the theory for the multi-zone model, that will be contributed to estimate the air pollution in large enclosures, such as shopping malls, atria buildings, atria terminals, and covered sports stadia.

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Trends in Evaluation Techniques for Leaching of Heavy Metals and Nutrients according to Sediment Resuspension in Rivers and Lakes (하천 및 호소 내 퇴적물 재부유에 따른 중금속 및 영양염류 용출량 평가기법 동향)

  • Sang-Gyu Yoon;Seoyeon Han;Haewook Kim;Ihn-Sil Kwak;Jinsung An
    • Journal of Soil and Groundwater Environment
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    • v.28 no.5
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    • pp.1-11
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    • 2023
  • The phenomenon of sediment resuspension in rivers and lakes causes contaminants (heavy metals and nutrients) accumulated in the sediment to leach into the overlying water. As a result, it can lead to changes in toxic effects and eutrophication in the aquatic ecosystem. In this regard, it is important to quantitatively determine the amount of contaminants leached during sediment resuspension. In this study, methods for assessing the amount of released contaminants and the types of contaminants potentially released due to sediment resuspension were studied and summarized. Methods for assessing leaching can be divided into three groups based on the principle of causing resuspension: (i) the oscillating grid chamber method, (ii) the mechanical stirrer method, and (iii) the shaker method. It was confirmed that the types of contaminants that can potentially be released include heavy metals bound to sulfides, as well as exchangeable and labile forms of heavy metals and nutrients. To effectively manage stable aquatic ecosystems in the future, a simplified leaching test method is needed to assess in advance the risks (i.e., changes in toxic effects and eutrophication) that sediment resuspension may pose to aquatic ecosystems.

Total Diet Studies as a Tool for Ensuring Food Safety

  • Lee, Joon-Goo;Kim, Sheen-Hee;Kim, Hae-Jung;Yoon, Hae-Jung
    • Toxicological Research
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    • v.31 no.3
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    • pp.221-226
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    • 2015
  • With the diversification and internationalization of the food industry and the increased focus on health from a majority of consumers, food safety policies are being implemented based on scientific evidence. Risk analysis represents the most useful scientific approach for making food safety decisions. Total diet study (TDS) is often used as a risk assessment tool to evaluate exposure to hazardous elements. Many countries perform TDSs to screen for chemicals in foods and analyze exposure trends to hazardous elements. TDSs differ from traditional food monitoring in two major aspects: chemicals are analyzed in food in the form in which it will be consumed and it is cost-effective in analyzing composite samples after processing multiple ingredients together. In Korea, TDSs have been conducted to estimate dietary intakes of heavy metals, pesticides, mycotoxins, persistent organic pollutants, and processing contaminants. TDSs need to be carried out periodically to ensure food safety.

Assessment on the Transition of Arsenic and Heavy Metal from Soil to Plant according to Stabilization Process using Limestone and Steelmaking Slag (석회석과 제강슬래그를 이용한 오염토양 안정화에 따른 비소 및 중금속의 식물체 전이도 평가)

  • Koh, Il-Ha;Lee, Sang-Hwan;Lee, Won-Seok;Chang, Yoon-Young
    • Journal of Soil and Groundwater Environment
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    • v.18 no.7
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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.

Analysis on the Seepage Behavior of Organic Contaminants in Soil (토양에서 유기화합물질의 침투 거동 연구)

  • Lee, Jun Ho;Han, Sun Hyang;Park, Kap Song
    • Journal of Korean Society on Water Environment
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    • v.29 no.4
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    • pp.489-496
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    • 2013
  • Ground water underlying soil is vulnerable to pollution by organic chemicals through their percolation through the soil system. This study was conducted to provide information on the seepage behavior of organic chemical contaminants in clay, silty and sandy soils. Chloroform, 1,1,1-trichloroethane and trichloroethylene are readily transported through the soil; their percolated mass were 4.6-19.2 percent of the total mass applied. Tetrachloroethylene, 1,2-dichlorobenzene and 1,3-dichlorobenzene were retarded by soils due to sorption. Between 0.6 and 4.8 percent of the material applied to the surface percolated within the experimental period. Carbon tetrachloride was attenuated considerably by passage through soils. Only 0.1-0.4 percent of the mass reached the groundwater. Significant degradation of bromoform was observed. Apparent breakdown of intermediates of the brominated compounds were detected. Transformations of the brominated compounds appear to be the result of both biological and chemical processes. The effect of soil type on the mobility of organic chemical contaminants was considerable. The organic contaminants moved faster in sandy soil than in either clay or silty soils.

FIXATION OF LEAD CONTAMINANTS IN Pb-DOPED SOLIDIFIED WASTE FORMS

  • Lee, Dong-Jin;Chung, David;Hwang, Jong-Yeon;Choi, Hyun-Jin
    • Environmental Engineering Research
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    • v.12 no.3
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    • pp.101-108
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    • 2007
  • Fixation of lead contaminants in the solidification/stabilization using Portland cement has been investigated by X-ray diffraction, scanning electron microscopy and compressive strength. The presence of lead was observed to produce lead carbonate sulfate hydroxide ($Pb_4SO_4(CO_3)_2(OH)_2$), lead carbonate hydroxide hydrate ($3PbCO_3{\cdot}2Pb(OH)_2{\cdot}H_2O$) and two other unidentified lead salts in cavity areas and was observed to significantly retard the hydration of cement. By 28 days, howevere, the XRD peaks of most of the lead precipitates have essentially disappeared with only residual traces of lead carbonate sulfate hydroxide and lead carbonate hydroxide hydrate evident. After 28 days of curing, hydration appears well advanced with a strong portlandite peak present though C-S-H gel peaks are not particularly evident. Lead species produced with the dissolution of lead precipitates are fixed into the cement matrix to be calcium lead silicate hydrate (C-Pb-S-H) during cement-based solidification.