• Title/Summary/Keyword: 중염소

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Meta-Analysis of Risk Factors for Contamination of Environmental Waters by Legionella (환경수계 레지오넬라균 오염 지표의 메타분석)

  • Zo, Young-Gun
    • Korean Journal of Microbiology
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    • v.49 no.4
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    • pp.424-428
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    • 2013
  • To identify risk factors for Legionella contamination, water quality variables routinely measured in examination of natural and city waters were meta-analyzed for significance of correlation to Legionella incidences. For evaluation of abundance of Escherichia coli as a risk factor, which is currently used as an indicator of Legionella contamination in an official guideline in Korea, odds ratio (OR) of above-cutoff total coliform counts for Legionella presence/absence was used as the effect size in the meta-analysis. The OR was estimated as 1.05 (0.36-3.12, 95% CI), and the probability of having identical odds reached 0.92. Also, ORs from individual studies showed significant heterogeneity (P=0.008), which contributed to 63% of total variance of the ORs. In the case of heterotrophic plate count (HPC), the OR for Legionella presence/absence was 2.72 (2.04-3.63) with highly significant deviation from identical odds (P<0.0001). ORs from different studies were seemingly homogeneous ($Q_{df=8}$=12.7, P=0.12). Turbidity and concentrations of chlorine, iron ion and cupper ion were other routine variables that could be considered as risk factors. However, statistical measures from different studies were not uniform enough to develop an appropriate effect size while the number of studies reporting the variables was also small (3-5). In conclusion, HPC appeared to be appropriate as indicator of Legionella contamination, rather than fecal bacteria contamination. HPC may imply abundance of habitats (amoebas and biofilms) of Legionella in water. This result warrants further studies for standardizing protocols and cutoff values to infer Legionella risks from HPC.

Effects of Fragmentation on the Bird Community in Agricultural Landscapes (농촌 경관에서 파편화가 조류 군집에 미치는 영향)

  • 박찬열;이우신
    • Korean Journal of Environment and Ecology
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    • v.16 no.1
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    • pp.22-33
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    • 2002
  • This study was conducted to investigate the effects of fragmentation on the bird community in Seongduck-ri and Hanggum-ri agricultural landscapes of Kangha-myon, Yangpyong-gun, Kyonggido. We analyzed the composition of tree species, forest environmental structures, structures of agricultural landscapes, avifaunas and guild structures. Number and density of tree species ranging from 6 to 10cm in D.B.H. were high in Seongduck-ri, but basal area was high in Hanggum-ri. Coverages of foliage layers under two meters and over 12 meters were high in Hanggum-ri. Meanwhile, Seongduck-ri agricultural landscapes consisted of twelve patches, dominated by Larix leptolepsis and Robinia pseudoacacia Hanggum-ri landscapes was composed of eleven patches, and dominated by Pinus rigida, Castanea crenate, Larix leptolepsis and paddy field. Dominant bird species showed the same order in two study areas, thirty-six species of birds were observed in Hanggum-ri landscapes, but twenty species were in Seongduck-ri landscapes. Number of species and density belonging to hole-, bush-, ground-nesting and water-, bush-, ground-foraging guild were high in Hanggum-ri landscapes. Number of species and density belonging to hole-nesting guild showed the high value in Hanggum-ri landscapes that was not fragmented. It could be attributed to the low human disturbance and relative high density of medium and large trees in D.B.H. Also, number of species and density belonging to bush-, ground- and water- foraging guild showed the high value in Hanggum-ri landscapes that had the high foliage amounts in the foliage layer under two meters. It will be related with the paddy field, dry field and brook, which patches covered the 28.4% of Hanggum-ri landscapes. Therefore, road not only dominate the heterogeneous patch in agricultural landscapes, but also easily cause the human disturbance. Thus, road construction would decrease the natural patch diversity and edge effects that are important for sustaining the diverse avifauna in agricultural landscapes.

Evaluation of Apparent Chloride Diffusion Coefficient and Surface Chloride Contents of FA concrete Exposed Splash zone Considering Crack Width (비말 지역에 노출된 FA 콘크리트의 균열을 고려한 겉보기 염화물 확산계수 및 표면 염화물량 평가)

  • Yoon, Yong-Sik;Kwon, Seung-Jun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.23 no.6
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    • pp.18-25
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    • 2019
  • The cracks occurred during service life of concrete structure should be considered in durability design, because of the concrete's material property which is weak in tensile strength. In this study, the fly ash concrete mixtures considering 2 levels of strength is designed and outdoor exposure tests are conducted for those concrete specimens. The exposure environment is set to a splash zone, and in order to evaluate the effect of crack width on the behavior of chloride diffusion, the crack width of up to 1.0 mm is generated at intervals of 0.1 mm at each concrete mixture. After that, apparent chloride diffusion coefficient and surface chloride contents are deducted considering 3 levels of exposure periods(180 days, 365 days, 730 days). The diffusion coefficients of two types of mixture increase with the increase of crack width, and the diffusion coefficients decrease with the increase of exposure periods. In addition, the effect of the crack width on the diffusion coefficient is reduced as the exposure periods increase, which is attributed to the extra hydrate by chloride ion reducing the diffusivity of concrete. The behavior of the surface chloride contents does not significantly change by the increase in crack width, compared to the behavior of apparent chloride diffusion coefficient. Also, In the high strength FA concrete mixture, the surface chloride contents are 78.9 % ~ 90.7 % than the normal FA strength concrete mixture. Thus, Surface chloride contents have correlation with the strength of concrete.

Products and pollutants of half dried sewage sludge and waste plastic co-pyrolysis in a pilot-scale continuous reactor (반 건조 하수슬러지와 폐플라스틱 혼합물의 파일롯 규모 연속식 열분해에 의한 생산물과 발생 오염물질)

  • Kim, YongHwa;Chun, Seung-Kyu
    • Journal of the Korean Applied Science and Technology
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    • v.34 no.2
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    • pp.327-337
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    • 2017
  • A continuous low temperature ($510^{\circ}C{\sim}530^{\circ}C$) pyrolysis experiment in a pilot-scale of 85.3 kg/hr was carried out by the mixed feedstock of half dried digested sewage sludge and waste plastics. As a result, the amount of pyrolysis gas generated was maximum 68.3% of input dry mass and scored $40.9MJ/Nm^3$ of lower heating value (LHV), and the percentage of air inflow caused by continuous pyrolysis was 19.6%. The oil was produced 4.2% of the input dry mass, and the LHV was 32.5 MJ/kg. The sulfur and chlorine contents, which could cause corrosion of the facility, were found to be 0.2% or more respectively. The carbide generated was 27.5% of the input dry mass which shows LHV of 10.2 MJ/kg, and did not fall under designated waste from the elution test. The concentration of carbon monoxide, sulfur oxides and hydrogen cyanide of emitted flu gas from pyrolysis gas combustion was especially high, and dioxin (PCDDs/DFs) was within the legal standards as $0.034ng-TEQ/Sm^3$. Among the 47 water pollutant contents of waste water generated from dry flue gas condensation, several contents such as total nitrogen, n-H extract and cyanide showed high concentration. Therefore, the merge treatment in the sewage treatment plants after pre-treatment could be considered.

Characteristics and Sampling of Dioxins/Furans from Emission Gas and Fly Ash Produced in Municipal Waste Incinerator (도시 소각로 쓰레기 소각후 생성된 폐가스 및 비산재중에 포함된 다이옥신류의 측정 및 특성고찰)

  • Lim, Chae-Hyun;Kim, Hee-Taik;Sohn, Jung-Hyun;Chang, Yoon-Seok
    • Applied Chemistry for Engineering
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    • v.8 no.5
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    • pp.790-795
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    • 1997
  • Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofuransfurans are the archetype of toxic chemicals. So it has absorbed public attention. The majors primary sources of PCDDS and PCDFs are chemical, thermal and photochemical reactions. Municipal solid waste incinerator facilities has been reported as the major contributors of dioxins to the environment. In this paper, Dioxins and furans were examined emission gas and fly ash produced during combustion in municipal solid waste incinerator. More effective method for sampling, extraction was described. The sample was extracted using a soxhlet method and purified using silicagel, alumina and carbon fibre HPLC to remove interfering compound. The extract was then analyzed by HRGC/HRMS. The result of this study showed recovery standard was good and the data resembled those of thermal processes. Total dioxins and furans were $1076.20pg/Nm^3$ and $1452.34pg/Nm^3$ respectively. The amount of highly chlorinated compound was more than that of lowly chlorinated compound. The 2,3,7,8-substituted TCDD was Just 0.34% of the total dioxins/furans amount.

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Durability and Crack Control of Concrete Using Fluosilicates Based Composite (규불화염계 복합 조성물을 혼입한 콘크리트의 균열제어 및 내구성)

  • Yun, Hyun-Do;Yang, Il-Seung;Kim, Do-Su;Khil, Bae-Su;Han, Seung-Gu
    • Journal of the Korea Concrete Institute
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    • v.18 no.1 s.91
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    • pp.57-64
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    • 2006
  • The crack presented in concrete structures causes a structural defect, the durability decrease, and external damages etc. Therefore, it is necessary to improve durability through the effort to control the crack. Fluosilicic acid($H_2SiF_6$) is recovered as aqueous solution which absorbs $SiF_4$ produced from the manufacturing of industrial-graded $H_3PO_4$ or HF. Generally, fluosilicates prepared by the reaction between $H_2SiF_6$ and metal salts. Addition of fluosilicates to cement endows odd properties through unique chemical reaction with the fresh and hardened cement. Mix proportions for experiment were modulated at 0.45 of water to cement ratio and $0.0{\sim}2.0%$ of adding ratio of fluosilicate salt based inorganic compound. To evaluate correlation of concrete strength and adding ratio of fluosilicate salt based inorganic compound, the tests were performed about design strength(21, 24, 27 MPa) with 0.5% of adding ratio of fluosilicate salt based inorganic compound. Applications of fluosilicate salt based inorganic compound to reduce cracks resulted from plastic and drying shrinkage, to improve durability are presented in this paper. Durability was evaluated as neutralization, chloride ion penetration depth, freezing thawing resistant tests and weight loss according reinforcement corrosion. It is ascertained that the concrete added fluosilicate salt based inorganic compound showed m ability to reduce the total area and maximum crack width significantly as compared non-added concrete. In addition, the durability of concrete improved because of resistance to crack and watertightness by packing role of fluosilicate salt based inorganic compound obtained and pozzolanic reaction of soluble $SiO_2$ than non-added concrete.

Improvement of Durability and Change of Pore Structure for Concrete Surface by the Penetrative Surface Protection Agent (함침계 표면보호제에 의한 콘크리트 표면의 세공구조 변화 및 내구성 향상)

  • Kang, Suk-Pyo;Kim, Jung-Hwan
    • Journal of the Korea Concrete Institute
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    • v.18 no.1 s.91
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    • pp.125-132
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    • 2006
  • Recently, surface finishing and protection materials were developed to restore performance of the deteriorated concrete and inhibiting corrosion of the reinforcing-bar. For this purpose, surface protection agent as well as coatings are used. Coatings have the advantage of low Permeability of $CO_2,\;SO_2$ and water. However, for coatings such as epoxy, urethane and acryl, long-term adhesive strength is reduced and the formed membrane of those is blistered by various causes. Also when organic coatings are applied to the wet surface of concrete, those have a problem with adhesion. On the other hand, surface protection agent penetrates into pore structure in concrete through capillary and cm make a dense micro structure in concrete as a result of filling effect. Furthermore, the chemical reaction between silicate from surface protection agent and cement hydrates can also make a additional hydration product which is ideally compatible with concrete body. The aim of this study is to examine the effect of penetrative surface protection agent(SPA) by evaluating several concrete durability characteristics. The results show that the concrete penetrated surface protection agent exhibited higher durability characteristics for instance, carbonation velocity coefficient, resistance to chemical attack and chloride ion penetration than the plain concrete. These results due to formation of a discontinuous macro-pore system which inhibits deterioration factors of concrete by changed the pore structure(porosity and pore size distributions) of the concrete penetrated surface protection agent.

Changes in the Concentrations of the Tap Water Chlorination By-Products by Heating during Cooking, and Human Ingestion Exposure (조리시 가열에 따른 수돗물 중 염소소독부산물의 농도 변화와 인체 섭취 노출)

  • 김희갑;이수형
    • Environmental Analysis Health and Toxicology
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    • v.14 no.1_2
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    • pp.35-43
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    • 1999
  • A number of disinfection by-products (DBPs) are formed as a result of the addition of chlorine into the public water supply and some of them have been suggested to cause adverse health effects on humans. However, the estimation of human ingestion exposure to each DBP has been performed simply by multiplying the concentration of a chemical in the cold tap water by the volume of water consumed during a given period of time. However, a questionnaire concerning water consumptions administered to sixty people residing in Chunchon showed that the volume of tap water consumed accounted for approximately 70% of the total volume of water consumed and that of heated water represented approximately 94% of tap water ingested. Heating durations for water-containing foods (e. g., soups and pot stews) and heated beverages (e. g., barley tea) were grouped into 10, 20, 30, and 35 minutes. Based on these time frames, an aluminum pot containing one liter of tap water was heated for the above respective time periods using a gas range to determine the variations of the concentrations of individual DBPs by heating. The pH and total residual chlorine were measured before and after heating. Collected water samples were carried to the laboratory and analyzed for eight DBPs and total organic carbon. Chloroform, bromodichloromethane, chloral hydrate, 1, 2-dichloro-2-propanone, 1, 1, 1-trichloropropanone, and dichloroacetonitrile were not detected following heating for 10 minutes and longer. The concentration of dichloroacetic acid (DCAA) was elevated with heating duration, resulting in the averages of 2.0, 3.1, 4.7, and 12 times the initial concentration, respectively, for 10, 20, 30, and 35 minute heating periods. On the other hand, the concentration of trichloroacetic acid (TCAA) decreased with heating duration, with 0.65, 0.40, 0.34, and 0.19 times lower than the initial concentration. Therefore, it is suggested that ingestion exposure to DCAA increases with heating duration but that ingestion exposure to TCAA decreases. In addition, while the amount of DCAA was elevated at the initial time periods (10 or 20 minutes) and then slowly decreased, that of TCAA was rapidly decreased. In conclusion, water-heating processes during cooking influence the concentrations of individual DBPs in the tap water, with lower levels for volatile DBPs and TCAA, and higher levels for DCAA. Therefore, concentration change needs to be taken into consideration in the estimation of human ingestion exposure to DBPs.

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Dioxins and Health: Human Exposure Level and Epidemiologic Evidences of Health Effects (다이옥신과 건강: 인체 노출 수준 및 건강영향에 대한 역학적 연구)

  • Jang, Jae-Yeon;Kwon, Ho-Jang
    • Journal of Preventive Medicine and Public Health
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    • v.36 no.4
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    • pp.303-313
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    • 2003
  • General information is summarized, that is necessary to introduce a scientific assessment of the human health and exposure issue concerning dioxin and dioxin-like compound. Scientific literatures were reviewed to assess the background exposures to the dioxin-like compounds for normal residents. Epidemiologic studies were also reviewed to assess malignant and nonmalignant sweets of dioxins. In 1997, the International Agency for Research on Cancer classified 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) as a human carcinogen, primarily based on occupational cohort studies. The US Environmental Protection Agency made the same decision in it's Draft Dioxin Reassessment. Epidemiologic evidences point to a generalized excess of all cancers, without any pronounced excess at specific sites. Reported non-cancer effects included a range of conditions affecting most systems. Among them, chloracne, elevation in gamma glutamyl transferase(GGT), and alterations in reproductive hormones are related to TCDO, Other adverse outcomes, such as lipid concentrations, diabetes, circulatory and heart diseases, immunologic disorders, neurobehavioral effects, and developmental outcomes require further study before their respective relationships to TCDD can be more definitively assessed.

Ecotoxicity Assessment of Leachate from Disposal Site for Foot-and-Mouth Disease Carcasses (구제역 가축 매몰지 침출수 독성영향평가)

  • Kim, Dongwoo;Yu, Seungho;Chang, Soonwoong;Lee, Junga
    • Journal of the Korean GEO-environmental Society
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    • v.15 no.8
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    • pp.5-11
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    • 2014
  • In this study, chemical analysis and ecotoxicity tests of leachate from disposal site for foot-and-mouth disease carcasses (FMD leachate) were conducted to collect fundamental data that will be used to develop environmental risk assessment tools for FMD leachate. For chemical analysis, concentration of $Cl^-$, $NH{_4}{^+}-N$, Korea standard method indicators for detection of leachate released from animal carcasses burial site into groundwater and NRN (Ninhydrin-Reactive Nitrogens), a newly suggested screening test indicator to detect groundwater contamination by FMD leachate, were assessed. For ecotoxicity tests, luminescent bacteria (V. fischeri), micro-algae (P. subcapitata) and water flea (D. magna) were selected as test species. Correlation analysis between the concentration of $Cl^-$, $NH{_4}{^+}-N$, NRN and the toxicity to V. fischeri was performed to identify the better indicators to monitor FMD leachate contamination. From regression analysis, the concentration of the indicators in FMD leachate contaminated sample that induced halfmaximal toxic effect to V. fischeri was evaluated. Results obtained from this study can be applied to assess the risk by FMD leachate and to establish the guideline to manage risk in relation to FMD leachate.