• Bulletin of the Korean Chemical Society
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• 제24권4호
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• pp.413-420
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• 2003

A gas chromatography/mass spectrometric assay method was developed for the simultaneous determination of neutral and bacis twenty-five disruptors $(ED_S)$ in frog and fish. Afther homogenization and sonication of 5 g of sample, purification was achieves in one step with a solid phase extraction procedure using silica gelflorisl. Eluton was performed with 50mL of acetone : n-hexane (1 : 9) solution. The eluate was concentrated to approximately 10uL and dissolves with 100 uL of hexane and analyzed by GC-MS (SIM). The peaks had good chromatographic properties and the extraction of these compounds from sample also gave relatively high recoveries with small variatoins. Detection limits were 0.1 ng/g for 4-nitrotoluene, benzophenone, hexachlorobenzene, atrazine, malathion, o,p-DDT, o,p-DDT and permethrin, and 0.2 ng/g for heptachlor epoxide, γ-chlordane, α-chlordane, p,p'-DDE, p,p'-DDD, cypermethrin and fenvalerate, and 0.3 ng/g for trifluralin, metribuzin, alachlor, dieldrin and p,p'-DDT, and 0.5 ng/g for heptachlor, aldrin and parathion, and 0.7 ng/g for endrin, and 0.8 ng/g for nitrofen. The recoveries were between 33 and 109%. The method was used to analyze twenty-five frogs and forty-six fishes fishes samples caught from various regions in Korea. Benzophenone was detected at concentration of up to 17.2 ng/g in frog or fish. Heptachlor, aldrin, γ-chlordane, p,p'-DDE, p,p'-DDD, endrin and o,p-DDD were detected at concentrations of 0.7-12.5 ng/g in frog or fish. Also significant leveles of dieldrin (up to 22.5 ng/g) were observed. The developed method may be valuable to be used to the national monitoring project of EDS in biota samples.

• 한국세라믹학회지
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• 제43권2호
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• pp.121-125
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• 2006

[ $LiFePO_4$ ] is one of the promising materials for cathode material of secondary lithium batteries due to its high energy density, low cost, environmental friendliness and safety. $LiFePO_4$ was synthesized by the solid-state reaction method at 500 - 800°C. The crystal structure of $LiFePO_4$ was analyzed by X-ray powder diffraction. The samples synthesized at 600 and $700^{\circ}C$ showed a single phase of a olivine structure. The particle sizes were increased and the specific surface areas were decreased with heating temperatures. The electrochemical performance was investigated by coin cell test. The discharge capacities at 0.1 C-rate were 118 mAh/g and 112 mAh/g at $600^{\circ}C,\;700^{\circ}C$, respectively. In an attempt to improve the electrical conductivity of cathode materials, $LiFePO_4/graphite$ composite was prepared with various graphite contents. The electrical conductivity and discharge capacity were increased with increasing the graphite contents in composite samples. The rate capabilities at high current densities were also improved.

• 한국광물학회지
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• 제24권3호
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• pp.225-234
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• 2011

2009년 3월 17일 채집된 황사 총시료(TSP)의 개별 입자에 대하여, 고분해 주사전자현미경 및 에너지분산 X선 분광분석을 이용한 광물학적 특성 및 혼합상태 분석을 실시하였다. 황사 입자들 중, 석영, 사장석, K-장석, 각섬석, 흑운모, 백운모, 녹니석, 방해석 등은 비교적 조립질 입자로 산출되며, 이들 입자는 앓은 극미립 일라이트질 점토광물 층으로 피복되어 있다. 극미립 점토광물 입자들은 또한 개별 점토 덩어리를 형성한다. 조립질 방해석 외에 나노섬유 방해석들이 개별적으로 또는 집합체로 큰 입자를 피복하거나 점토광물과 함께 덩어리를 형성한다. 입자의 주 광물에 따라 광물학적 분류를 실시하고 빈도를 구하였다. 이번 TSP의 단일입자 광물학적 특성 및 혼합상태는 기존의 $PM_{10}$ 분석 결과와 거의 차이가 없었다.

• 자원환경지질
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• 제53권3호
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• pp.297-306
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• 2020

보오크사이트로부터 알루미나를 생산하는 Bayer 공정 부산물인 레드머드는 높은 pH와 나트륨(Na)의 함량으로 폐기물로 분류되어, 발생량을 줄이거나 재활용하는 공정의 개발은 환경적으로 중요한 이슈이다. 본 연구에서는 레드머드 내 다량 함유된 철(Fe)을 자원가치를 갖는 품위(56wt.%) 이상으로 향상시키고자 레드머드에 활성탄과 황을 혼합하여 마이크로웨이브 가열 시험을 수행하였다. 가열 소성과정에서 레드머드 혼합물 분말시료는 유리화된 다공성 구조의 결합체로 변화되었으며, X-선 회절분석을 통하여 산출물은 침철석, 영가철(Fe⁰, iron), 자류철석(Fe_1-xS) 및 황철석(FeS₂) 등으로 구성됨을 확인하였다. 가열 소성 결과물은 왕수분해를 통하여 Fe을 용해시키고, NaCl을 첨가하여 Fe을 침전 회수하였다. 레드머드 내 Fe의 회수는 시험 조건별로 상이하게 나타났으며, 단순히 레드머드를 마이크로웨이브 가열한 시료 내 Fe은 그 함량이 49.0wt.% 였다. 그러나, 활성탄을 첨가한 시료 및 활성탄과 황을 첨가한 레드머드 시료의 가열 소성 결과물 내 Fe의 함량은 각각 58.0wt.%, 59.5wt.% 로서 철 자원가치 품위인 56wt.%를 초과하였다.

• 한국산업보건학회지
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• 제6권1호
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• pp.17-27
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• 1996

This study was designed to survey exposure levels of formaldehyde among workplaces in some plywood industries and to compare three sampling methods including the impinger method(IM, NIOSH method No. 3500), the solid sorbent tube method(SS, NIOSH method No. 2541), and the passive bubbler monitor method(PB, SKC). The survey was conducted in seven particle board manufacturing factories, two resin manufacturing factories and two plywood manufacturing factories in Incheon area during the period from March 6 to April 20, 1995. The workplaces included were the hot/cold press, the roller/spreader, the soaking/drying, and the reaction/mixing areas. The results were as follows; 1. The average(GM, GSD) concentrations of formaldehyde by sampling methods were 0.11(4.43) ppm by IM, 0.27(2.03) ppm by SS, and 0.29(2.04) ppm by PB, respectively. The concentrations by 1M method were statistically very significantly lower than those of SS and PB methods, particularly at low air borne concentrations of formaldehyde (p<0.001). 2. The area average concentrations of formaldehyde by workplaces measured with PB bubblers were 0.23(2.08) ppm from the press, 0.23(1.77) ppm from the spreader, 0.24(1.51) ppm from the soaking, and 0.46(1.96) ppm from the reaction areas, respectively. The personal average concentrations of formaldehyde by workplaces measured with PB bubblers were 0.30(1.77) ppm from the press, 0.33(1.54) ppm from the spreader, 0.36(1.46) ppm from the soaking, and 0.84(1.19) ppm from the reaction areas, respectively. 3. No statistically significant differences of formaldehyde concentrations among workplaces except the reaction area(p<0.001) were found. 4. Formaldehyde concentrations from personal samples were higher than those of from area sam pies in all workplaces studied. But no statistically significant differences of formaldehyde concentrations both area and personal samples were found. In conclusion, this study found that although formaldehyde concentrations in some plywood industries in Incheon area were below the regulatory limit of 1 ppm, they were over the limits recommended by NIOSH and ACGIH. This study also suggests that the impinger method may underestimate true formaldehyde concentrations. It implies that there will be more workplaces not meeting current regulatory limit if either the solid sorbent or passive bubbler methods were used instead of the impinger method. It is suggested that passive monitors will be a reasonable alternative for area and personal sampling of formaldehyde if the accuracy and validity of passive monitors be verified before use.

• 한국습지학회지
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• 제9권1호
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• pp.107-114
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• 2007

This study aimed to investigate the hexachlorobenzene (HCB) dechlorinating ability of sediment microbes collected from a natural canal receiving secondary effluents from an industrial estate and nearby factories. Nine sites along the stream and one in the estuary in the Gulf of Thailand into which the canal spills were specified and sampling for sediment and water. Preliminary analysis of the sediments showed that the first four sites nearest to the discharging location were contaminated by HCB within the range of 0.18 to 1.25 ppm. Apart from that, 1,3,5-trichlorobenzene which has never been commercially produced or used in any manufacturing processes except for the transformation from higher chlorinated benzene was also identified in the range of 0.16 to 0.24 ppm. This suggested a possibility of sporadically HCB contamination in this stream. Of more important, people in the community along this canal earn their living by coastal fishery; hence, posing a risk of spreading HCB and its less chlorinated congeners via food chain from caught marine creatures to human. As a result, there is an urgent need to understand the behavior of HCB dechlorination in this stream sediment which can lead to a clean-up action in the future. Serum bottles with sediment slurries (sediment to water ratio of 1:1 (v/v) and filtered to remove particles larger than 0.7 mm) from each site were inoculated with 2 mg/l of HCB, kept anaerobically in the dark at room temperature without any nourishment, and analyzed for HCB and its less-chlorinated congeners every 6 days. Total chemical oxygen demand, suspended solids, and volatile suspended solids were in the range of 21,492-73,584, 158,100-518,100 and 6,000-32,700 mg/l, respectively. It was found that all sediment slurries began to dechlorinate HCB in 12 to 30 days and the HCB was completely removed within 42 to 60 days or so. On the other hand, there was no HCB dechlorination occurred in the controlled set which was sterilized by autoclaving prior to the addition of HCB. This implies that the HCB transformation was solely due to microorganisms' activities. HCB was dechlorinated principally via pentachlolobenzene to 1,2,3,5-tetrachlorobenzene and terminated at 1,3,5-trichlorobenzene which is the major pathway as reported by many researchers. Dichlorobenzene has not been detected in any samples within the dechlorination period of 60 days. The results indicate that the microbial matrix in the sediment of this stream has an outstanding capability to dechlorinate HCB. Existing substrates and nutrients which mainly sorbed onto the solid phase and the typical temperature in Thailand were sufficient and suitable to promote the activities of these HCB-dechlorinating microbes.

• Asian Journal of Atmospheric Environment
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• 제11권2호
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• pp.96-106
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• 2017

In this study, measurements of size-segregated particulate matter (PM) emitted from the combustion of rice straw, pine needles, and sesame stem were conducted in a laboratory chamber. The collected samples were used to analyze amounts of organic and elemental carbon (OC and EC), water-soluble organic carbon (WSOC), humic-like substances (HULIS), and ionic species. The light absorption properties of size-resolved water extracts were measured using ultraviolet-visible spectroscopy. A solid-phase extraction method was first used to separate the size-resolved HULIS fraction, which was then quantified by a total organic carbon analyzer. The results show that regardless of particle cut sizes, the contributions of size-resolved HULIS ($=1.94{\times}HULIS-C$) to PM size fractions ($PM_{0.32}$, $PM_{0.55}$, $PM_{1.0}$, and $PM_{1.8}$) were similar, accounting for 25.2-27.6, 15.2-22.4 and 28.2-28.7% for rice straw, pine needle, and sesame stem smoke samples, respectively. The $PM_{1.8}$ fraction revealed WSOC/OC and HULIS-C/WSOC ratios of 0.51 and 0.60, 0.44 and 0.40, and 0.50 and 0.60 for the rice straw, pine needle, and sesame stem burning emissions, respectively. Strong absorption with decreasing wavelength was found by the water extracts from size-resolved biomass burning aerosols. The absorption ${\AA}ngstr{\ddot{o}}m $ exponent values of the size-resolved water extracts fitted between 300 and 400 nm wavelengths for particle sizes of $0.32-1.0{\mu}m$ were 6.6-7.7 for the rice straw burning samples, and 7.5-8.0 for the sesame stem burning samples. The average mass absorption efficiencies of size-resolved WSOC and HULIS-C at 365 nm were 1.09 (range: 0.89-1.61) and 1.82 (range: 1.33-2.06) $m^2/g{\cdot}C$ for rice straw smoke aerosols, and 1.13 (range: 0.85-1.52) and 1.83 (range: 1.44-2.05) $m^2/g{\cdot}C$ for sesame stem smoke aerosols, respectively. The light absorption of size-resolved water extracts measured at 365 nm showed strong correlations with WSOC and HULIS-C concentrations ($R^2=0.89-0.93$), indicating significant contribution of HULIS component from biomass burning emissions to the light absorption of ambient aerosols.

• Advances in environmental research
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• 제6권3호
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• pp.159-171
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• 2017

A successful oil well drilling depends largely on a good mud Program. During drilling, mud provides sufficient hydrostatic pressure, removes drill cuttings and cools drill bits. Mud additives are always required to provide sufficient hydrostatic pressure to ensure borehole stability. Barium Sulphate ($BaSO_4$) also known as barite is the prevalent weighting material but there is needed to develop local materials to augment the use of Barite. The present search is concerned on the early Carboniferous succession exposed in Um Bogma Formation, west central Sinai, Egypt as a new weighting agent in drilling fluids. The increases in the cost of drilling fluids and a shortage of using barite have introduced the locale dolomite as alternative weighting materials. The rheological properties of mud drilling samples weighted by local dolomite samples are being examined and investigated to know its potential to be used as a weighting material in drilling mud. Two mud samples were prepared which comprised of fresh water, caustic soda, bentonite and the weighting material. The weighting materials are added to achieve the required density. The first sample: Water-based mud with commercial barite of density between 10.00 lb/gm and 18.00 lb/gm. The second sample: Water-based mud with dolomite of density between 10.00 lb/gm and 18.00 lb/gm. These samples were analyzed and the density, rheological properties, aging of barite and dolomite and solid contents were investigated. At 10.00 lb/gm, the yield point of dolomite was $20.00lb/100ft^2$ and barite $22.00lb/100ft^2$ while the 10 second gel strength of dolomite was $30.00lb/100ft^2$ and $22.00lb/100ft^2$ for barite. Similarly, little difference was observed in plastic and apparent viscosities. At 10.00 lb/gm, the plastic and apparent viscosities of dolomite were 8.00 cp and 20.00 cp while barite was 8.00 cp and 24.00 cp. The result show that dolomite mud sample gave a little higher yield point and gel strength than barite mud sample. Therefore, dolomite has the potential to be used as weighting material in drilling mud in place of barite thereby enhancing the local content initiative of the government. When dolomite is sourced locally and used it will reduce overall mud and drilling costs.

• 한국환경농학회지
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• 제33권4호
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• pp.381-387
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• 2014

BACKGROUND: Garlic (Allium sativum) extract has been allowed as commercial biopesticide material for pesticidal activity in the Environmentally-friendly Agriculture Promotion Act. Nine commercial biopesticides containing A. sativum extract have been marketed in Korea. However, the analytical method of the active substances in these materials has not been studied. METHODS AND RESULTS: Cartridge clean-up method for the determination of dimethyl disulfide(DMDS), diallyl disulfide(DADS), and diallyl trisulfide(DATS) in biopesticides containing A. sativum extract was developed and validated by gas chromatography(GC). The clean-up method was optimized using hydrophilic lipophilic balance (HLB) solid phase extraction(SPE) cartridges for the bioactive sulfides in biopesticides containing A. sativum extract, and the eluate was analyzed to quantify the DMDS, DADS, and DATS using the GC. The developed method was validated, and the LOQ and recovery rates of DMDS, DADS, and DATS were 0.226, 0.063, and $0.051mg\;L^{-1}$ and 80.6, 84.8, and 73.1%, respectively. From the nine commercial biopesticide samples, contents of DMDS, DADS, and DATS were analyzed using the developed method and results showed $2.3mg\;L^{-1}$, respectively. CONCLUSION: The developed method could be used in determining the quality of biopesticides for the manufacture of commercial biopesticides containing A. sativum extract.

• 한국환경보건학회지
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• 제40권6호
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• pp.435-441
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• 2014

Objectives: Bisphenol A, or BPA, is a chemical component in polycarbonate plastic with which many people come into contact every day. A great deal of controversy has arisen over its safety since this material, which is known to disrupt the human endocrine system and cause neurological difficulties and cancer, is commonplace in beverage containers, food can liners, and receipt paper rolls. In this study, we determined the levels of exposure to BPA of workers in the service industry depending on the number of receipts contacted. Methods: The participants were 16 male and 18 female workers employed in the service industry. Using a questionnaire, we investigated general and job characteristics. Urine samples were collected and analyzed by the LC-MS/MS technique after enzymatic hydrolysis and solid phase extraction (SPE). Results: The geometric mean (GM) concentration of urinary BPA from all subjects was 1.02 ng/ml. Workers were exposed significantly to more BPA according to the number of receipts they contacted, their work experience, and working hours per day. The BPA concentration of those who touched more than 100 receipts per day was 3.09 ng/ml, while that of the other participants was 0.61 ng/ml. It was shown that wearing gloves can protect from BPA exposure. Conclusion: We determined the urinary BPA concentrations of workers in service industry and found that the contact with receipts could increase the BPA exposure of service workers.