• 한국균학회지
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• 제28권2호
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• pp.93-96
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• 2000

완효성비료원을 혼합처리해서 배양시 0.1%와 0.5% 첨가구의 경우 잡균오염율은 나타나지 않았고 무처리에 비해서 배양일수가 약간 빨라졌고 초발이 소요일수는 $2{\sim}3$일 정도 빨라졌으며 수량성에 있어서는 수량이 모두 증가하였으나$(10{\sim}28%)$, 첨가량이 증가할수록 수량성과 생체효율성은 감소하는 경향을 보였다. 완효성비료 첨가배지의 화학성분은 첨가량이 많아질수록 총질소, 암모니아태 및 질산태 질소, 칼리, 인산등은 증가하였다. 완효성비료처리배지에서 생산된 버섯자실체의 이화학적 특성은 암모니아태 질소와 질산태 질소의 경우 무처리구 보다 낮은 경향이었으며 다른 무기성분들은 무첨가와 비슷한 경향을 보였다.

• 한국세라믹학회지
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• 제49권6호
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• pp.608-613
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• 2012

We investigated the property changes of MgO powders sintered at temperatures ranging from $700^{\circ}C$ to $1900^{\circ}C$ for 5minutes at a pressure of 2.7 GPa for a high-pressure high-temperature(HPHT) diamond synthesis process. The physical properties of the sintered MgO powders were characterized by optical microscopy, field emission scanning electron microscopy (FE-SEM), Vickers hardness tests, and by the apparent density, and X-ray diffractometry. An optical micro-analysis showed that white MgO powders became black after sintering due to carbon contamination from the graphite heat source. FE-SEM revealed the growth in the grain size of the MgO powders from $0.3{\mu}m$ to $50{\mu}m$ after sintering at $1700^{\circ}C$. The hardness and apparent density increased to $1800^{\circ}C$ while the samples were dedensified at $1900^{\circ}C$ due to the growth of isolated pores. According to the XRD analysis, no phase transformation occurred in the MgO powders. These results suggest that HPHT-sintered MgO powders can show an accelerated sintering process characterized by grain neck growth, pore connections, isolated pore growth and dedensification in 5 minutes, while these processes with the conventional sintering process take at least 5 hours.

• 멤브레인
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• 제31권6호
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• pp.393-403
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• 2021

생체 내 변화에서 효소는 중요한 촉매이다. 효소의 안정성과 재사용성은 촉매 과정에서 중요한 요소이다. 적합한 기질에 효소 고정화는 특정 미세환경의 조성을 통해 효소 활동성을 높인다. 다양한 종류의 분리막이 각각의 생체적합성과 막 표면의 친수성/소수성 조절 용이도에 따라 기질로 사용되었다. 본 논문에서는 셀룰로스, 폴리아크릴로니트릴(PAN), 폴리디메틸실록산(PDMS), 폴리비닐리덴플루오라이드(PVDF), 폴리에테르설폰(PES) 고분자 분리막이 소개되고 토의되었다. 고정화 효소를 이용한 유기오염물의 생물적 분해는 제약 회사 및 섬유 회사 등에서 발생하는 오염물질을 친환경적으로 감소할 수 있는 방법이다. 효소 고정화 생물반응기(EMBR)로 기름의 가수분해를 제어할 수 있고 이를 통해 탄소 배출량 감소 및 환경오염을 줄일 수 있다. EMBR로 만들 수 있는 바이오에탄올과 바이오디젤은 화석 연료의 대체제이다.

• Nuclear Engineering and Technology
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• 제54권8호
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• pp.2792-2800
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• 2022

In the core of the WWR-K reactor, a long-term irradiation of tristructural isotopic (TRISO)-coated fuel particles (CFPs) with a UO₂ kernel was carried out under high-temperature gas-cooled reactor (HTGR)-like operating conditions. The temperature of this TRISO fuel during irradiation varied in the range of 950-1100 ℃. A fission per initial metal atom (FIMA) of uranium burnup of 9.9% was reached. The release of gaseous fission products was measured in-pile. The release-to-birth ratio (R/B) for the fission product isotopes was calculated. Aspects of fuel safety while achieving deep fuel burnup are important and relevant, including maintaining the integrity of the fuel coatings. The main mechanisms of fuel failure are kernel migration, silicon carbide corrosion by palladium, and gas pressure increase inside the CFP. The formation of gaseous fission products and carbon monoxide leads to an increase in the internal pressure in the CFP, which is a dominant failure mechanism of the coatings under this level of burnup. Irradiated fuel compacts were subjected to electric dissociation to isolate the CFPs from the fuel compacts. In addition, nondestructive methods, such as X-ray radiography and gamma spectrometry, were used. The predicted R/B ratio was evaluated using the fission gas release model developed in the high-temperature test reactor (HTTR) project. In the model, both the through-coatings of failed CFPs and as-fabricated uranium contamination were assumed to be sources of the fission gas. The obtained R/B ratio for gaseous fission products allows the finalization and validation of the model for the release of fission products from the CFPs and fuel compacts. The success of the integrity of TRISO fuel irradiated at approximately 9.9% FIMA was demonstrated. A low fuel failure fraction and R/B ratios indicated good performance and reliability of the studied TRISO fuel.

• 한국수산과학회지
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• 제55권5호
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• pp.514-523
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• 2022

Concentrations of perfluoroalkyl substances (PFASs) were measured in seawater, sediment, and biota collected from Gunsan coast, Korea to investigate their occurrence, distribution, and risk of exposure to humans through seafood consumption. The total concentrations of PFASs in seawater, sediment, and biota ranged from 5.97 to 74.9 ng/L, 0.01 to 13.3 ng/g dry weight, and 0.02 to 5.73 ng/g wet weight, respectively. Predominant PFAS compounds differed across matrices, indicating that the distribution of PFASs in multiple environmental samples is governed by their carbon-chain length. The concentrations of PFASs in seawater were significantly negatively correlated with salinity (P<0.01), suggesting terrestrial input (including land-used PFASs) as the major source of PFAS contamination in coastal environments. The estimated daily intakes (EDIs) of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) through seafood consumption were 0.05 and 0.06 ng/kg body weight/day, respectively. The EDIs of PFOA and PFOS measured in this study were lower those the proposed by the United States Environmental Protection Agency and Canada guidelines, indicating limited health risk for Korean population from PFASs through consumption of seafood from Gunsan coastal environment.

• 한국지하수토양환경학회지:지하수토양환경
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• 제29권3호
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• pp.1-13
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• 2024

This study investigated the hydrogeochemical and microbiological characteristics of freshwater on Ulleung Island, a volcanic island in the Ulleung Basin on the East Coast of Korea. The shallow groundwater (CSW, NRGW) and the surface water (SISW) samples are classified as Na-HCO₃ type, reflecting an alkaline rock type and an oxidizing environment due to the influence of a highly permeable pyroclastic rock layer. In contrast, the deep groundwater sample (DMW) is classified as Ca-HCO₃ type, suggesting the influence of deep-sourced carbon dioxide and reducing conditions. Microbial communities in the water samples are generally dominated by Proteobacteria, with the relative abundance of major genera varying depending on water quality and environmental conditions. Network analysis reveals the ecological characteristics of microbial communities adapted to specific environments. The presence of pathogenic genera in the shallow groundwater suggests potential groundwater contamination, necessitating appropriate management to ensure its use as drinking water or domestic water. The findings of this study provide valuable insights into the ecological characteristics of Ulleung Island's groundwater resources and can inform future groundwater management strategies.

• 대한환경공학회지
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• 제38권12호
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• pp.641-646
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• 2016

토양 유기물은 농작물에 영양분을 공급하는 중요한 토양 구성분이며 오염물질의 이동을 감소시켜 인체 및 생태에 미치는 영향을 완충하는 역활을 한다. 최근 지구온난화를 야기하는 온실기체의 싱크탱크 역활이 부각되면서 토양 유기물에 대한 조사 및 관리방안에 대한 관심이 고조되고 있다. 본 연구의 목적은 첫째, 환경부 토양측정망 495개 지점에서 채취한 토양의 유기물함량을 측정하여 지역별, 토지용도별 토양 유기물함량을 파악하고자 하였고 둘째, 토양 유기물 함량 측정방법인 Tyurin산화법과 강열감량법(LOI)의 상관관계를 조사하였다. Tyurin법과 강열감량법으로 토양 유기물 함량을 조사한 결과 평균은 각 각 1.90%, 2.92%로 나타났다. 토지용도별 유기물 함량 순서는 Tyurin법 및 강열감량법 모두 유사하였다. 여전히 자연환경 요소가 많이 남아있거나 토양으로 유기물 유입이 지속적으로 일어나는 임야, 종교용지, 공원은 비교적 높은 유기물함량을 보이나, 유기물 유입이 상대적으로 적은 대지와 대부분 사질토양으로 구성된 학교용지는 낮은 유기물함량을 보였다. Tyurin법과 강열감량법간 회귀분석결과 y(Tyurin) = 0.6257x(LOI) + 0.0602 (P-value < 0.001)와 같은 회귀식이 얻어졌고 결정계수 $R^2=0.749$로 나타나 상관성이 높았다. Tyurin법과 강열감량법을 비교한 결과 강열감량법의 결과치가 Tyurin법에 비해 크게 측정되지만 Tyurin법과 상관관계가 성립되는 바 여러 토지용도에서 많은 양의 토양시료를 측정해야 하는 목적에서는 강열감량법 적용도 가능할 것으로 판단된다.

• 한국산업보건학회지
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• 제25권3호
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• pp.301-311
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• 2015

Objectives: Operators of overhead traveling crane in a ship assembly factory perform work to transmit large vessel blocks to an appropriate working process. Hazardous matters such as metal dusts, carbon monoxide, carbon dioxide, ozone, loud noise and fine particles are generated by variable working activities in the factory. The operators could be exposed to the hazardous matters during the work. In particular, welding fumes comprised of ultra fine particles and heavy metals is extremely hazardous for humans when exposing a pulmonary through respiratory pathway. Occupational lung diseases related to welding fumes are increasingly on an upward tendency. Therefore, the objective of this study is to assess properly unknown occupational exposure to the welding fumes among the operators. Methods: This study intended to clearly determine an equivalence check whether or not chemical constituents and composition of the dusts, which existed in the driver's cab, matched up with generally known welding fumes. Furthermore, computational fluid dynamics program(CFD) was used to identify a ventilation assessment in respect of a contamination distribution of welding fumes in the air. The operators were investigated to assess personal exposure levels of welding fumes and respirable particulate. Results: The dust in an operation room were the same constituents and composition as welding fumes. Welding fumes, which caused by the welding in a floor of the factory, arose with an ascending air current up to a roof and then stayed for a long time. They were considered to be exposed to the welding fumes in the operation room. The personal exposure levels of welding fumes and respirable particulate were 0.159(n=8, range=0.073-0.410) $mg/m^3$ and 0.138(n=8, range=0.087-0.178) $mg/m^3$, respectively. They were lower than a threshold limit value level($5mg/m^3$) of welding fumes. Conclusions: These findings indicate that an occupational exposure to welding fumes can exist among the operators. Consequently, we need to be keeping the operators under a constant assessment in the operator process of overhead traveling crane.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2000년도 춘계학술발표대회
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• pp.89-91
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• 2000

Polynuclear aromatic hydrocarbon (PAH) compounds are highly carcinogenic chemicals and common groundwater contaminants that are observed to persist in soils. The adherence and slow release of PAHs in soil is an obstacle to remediation and complicates the assessment of cleanup standards and risks. Biological degradation of PAHs in soil has been an area of active research because biological treatment may be less costly than conventional pumping technologies or excavation and thermal treatment. Biological degradation also offers the advantage to transform PAHs into non-toxic products such as biomass and carbon dioxide. Ample evidence exists for aerobic biodegradation of PAHs and many bacteria capable of degrading PAHs have been isolated and characterized. However, the microbial degradation of PAHs in sediments is impaired due to the anaerobic conditions that result from the typically high oxygen demand of the organic material present in the soil, the low solubility of oxygen in water, and the slow mass transfer of oxygen from overlying water to the soil environment. For these reasons, anaerobic microbial degradation technologies could help alleviate sediment PAH contamination and offer significant advantages for cost-efficient in-situ treatment. But very little is known about the potential for anaerobic degradation of PAHs in field soils. The objectives of this research were to assess: (1) the potential for biodegradation of PAH in field aged soils under denitrification conditions, (2) to assess the potential for biodegradation of naphthalene in soil microcosms under denitrifying conditions, and (3) to assess for the existence of microorganisms in field sediments capable of degrading naphthalene via denitrification. Two kinds of soils were used in this research: Harbor Point sediment (HPS-2) and Milwaukee Harbor sediment (MHS). Results presented in this seminar indicate possible degradation of PAHs in soil under denitrifying conditions. During the two months of anaerobic degradation, total PAH removal was modest probably due to both the low availability of the PAHs and competition with other more easily degradable sources of carbon in the sediments. For both Harbor Point sediment (HPS-2) and Milwaukee Harbor sediment (MHS), PAH reduction was confined to 3- and 4-ring PAHs. Comparing PAH reductions during two months of aerobic and anaerobic biotreatment of MHS, it was found that extent of PAHreduction for anaerobic treatment was compatible with that for aerobic treatment. Interestingly, removal of PAHs from sediment particle classes (by size and density) followed similar trends for aerobic and anaerobic treatment of MHS. The majority of the PAHs removed during biotreatment came from the clay/silt fraction. In an earlier study it was shown that PAHs associated with the clay/silt fraction in MHS were more available than PAHs associated with coal-derived fraction. Therefore, although total PAH reductions were small, the removal of PAHs from the more easily available sediment fraction (clay/silt) may result in a significant environmental benefit owing to a reduction in total PAH bioavailability. By using naphthalene as a model PAH compound, biodegradation of naphthalene under denitrifying condition was assessed in microcosms containing MHS. Naphthalene spiked into MHS was degraded below detection limit within 20 days with the accompanying reduction of nitrate. With repeated addition of naphthalene and nitrate, naphthalene degradation under nitrate reducing conditions was stable over one month. Nitrite, one of the intermediates of denitrification was detected during the incubation. Also the denitrification activity of the enrichment culture from MHS slurries was verified by monitoring the production of nitrogen gas in solid fluorescence denitrification medium. Microorganisms capable of degrading naphthalene via denitrification were isolated from this enrichment culture.

• 대한환경공학회지
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• 제33권3호
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• pp.202-211
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• 2011

본 연구는 소양호를 대상으로 장기간 동안 다매체 내 수은 농도 분포를 조사하였으며 소양호 총수은(TM; total mercury) 농도는 $1.17{\pm}1.09ng/L$ 나타났다. 표층수 총 수은 농도를 보면 시간적 및 공간적 변이에 대한 통계적 유의성을 찾아볼 수 없었으나, 탁도 및 입자성 유기탄소(particulate organic carbon; POC)의 농도와 뚜렷한 양의 상관성(P-value<0.01)이 있는 것으로 관측되었다. 또한 소양호의 경우 수은 유입원이 선행연구에서 언급된 대기 침적보다는 장마철 runoff로 인한 유입이 더 중요하다는 것을 나타낸다. 어류 내 수은은 한강과 소양호에서 총 22종의 어류를 채취하였으며, 어류 내 평균 총수은 농도는 0.073 ppm(습중량)으로 나타나, 우리나라의 기준치(0.5 ppm) 및 미국 EPA의 기준치(0.3 ppm)에 비해 낮은 농도를 보였다. 그러나 미국 EPA의 RfD(reference dose)를 바탕으로 본 연구에서 계산된 적정 기준치인 0.07 ppm을 상회하는 어류가 전체의 42%를 차지해 우리나라만의 어류섭취 관리대책이 필요하다. 어류를 채취한 세 지점, 한강, 신이리, 양구는 동일한 종에서 뚜렷하게 다른 농도 분포를 보였는데, 상류일수록 더 높은 농도를 나타냈다. 이는 호수의 부영양화 차이로 인한 지점별 어류 성장 속도의 차이가 원인인 것으로 생각된다. 소양호 저서퇴적물의 수은 농도 분포는 $69.9{\sim}98.3{\mu}g/kg$으로 나타나 미국 미네소타 주의 Voyageurs National Park에서의 연구 결과($102{\sim}364{\mu}g/kg$)보다 약간 낮게 나타났다.