• 환경위생공학
• /
• 제16권4호
• /
• pp.69-76
• /
• 2001

The catalytic oxidation of volatile organic compounds (VOCs), which were benzene and toluene, was studied in the supercritical carbon dioxide($SC-CO_2$) media. In $SC-CO_2$ media, the deep oxidation conversion of VOCs was increased with the temperature and pressure. The deep oxidation conversion in SC -$CO_2$ media is better than that in air media at same pressure condition. This can be explained by the solubility of VOCs in $SC-CO_2$. The many intermediates produced by the partial oxidation of VOCs were detected from off-line samples. The intermediates were Identified as benzene, toluene, benzaldehyde, phenol, naphthalene, 1,1`-biphenyl, benzoic acid, 3-methylphenol, 1,1'-(1,2-ethanediyl)bis- benzene, 1,1'-(1,2-ethene- diyl)bis-benzene, anthracene, and so on. The amount of intermediates was decreased as the molar radio of oxygen to carbon dioxide was decreased. When the molar ratio of oxygen to carbon dioxide was 1 : 16, the deep conversion was kept constant. Thus, the catalytic oxidation process in $SC-CO_2$ media can be combined on-line with supercritical fluid extraction of environmental matrices and supercritical regeneration of used adsorbent. Thus, the nontoxic $SC-CO_2$ media process was suggested as the new VOCs control technology.

• 한국해양학회지:바다
• /
• 제26권2호
• /
• pp.110-123
• /
• 2021

시화호 인근 연안 퇴적물에서 유기물 분해 특성, 퇴적물로부터의 영양염 용출 및 주요 조절요인을 파악하기 위해 공극수와 퇴적물 내 지화학 성분, 혐기성 유기물 분해율, 황산염 환원율 및 저층 영양염 용출률을 측정하였다. 연구정점은 소래포구 인근 정점(E0), 송도갯벌 정점(E1), 오이도 선착장 부근 정점(E3), 시화 조력발전소 수문 앞 정점(E5)으로 선정하였다. 유기탄소와 공극수 내 암모니아, 인산염 농도는 정점 E0에서 가장 높게 나타났으며, 외측 해역(정점 E1, E3, E5)으로 갈수록 점진적으로 감소하였다. 혐기성 유기물 분해율과 황산염 환원율은 정점 E0에서 각각 260.6 mmol C m^-2 d^-1와 91.4 mmol S m^-2 d^-1로 외측 정점들보다 각각 4-9배, 6-54배 높게 나타났다. 혐기성 유기물 분해에서 황산염 환원이 차지하는 비율은 정점 E3, E5에서 11-23%로 미미한 것으로 나타났으나, 정점 E0, E1에서는 47-70%로 황산염 환원에 의해 혐기성 유기물 분해가 주도되는 것으로 나타났다. 또한, 혐기성 유기물 분해율과 황산염 환원율은 용존 유기탄소와 상관성이 매우 높은 것으로 나타났다(r² = 0.795, 0.777). 한편, 정점 E0, E1, E3에서 퇴적물로부터 용출된 무기질소와 무기인은 각각 일차생산자가 요구하는 무기질소와 무기인의 120-510%와 26-178%를 공급하는 것으로 나타났다. 이상의 결과들은, 시화호 인근 연안 퇴적물 내 유기물 분해는 이용 가능한 용존 유기탄소의 공급에 의해 조절되고 있으며, 과도한 유기물 분해는 저층 영양염 용출을 촉진시켜 부영양화를 야기할 수 있음을 의미한다.

• 한국해양학회지:바다
• /
• 제8권3호
• /
• pp.317-326
• /
• 2003

연안수에서 유기 화합물의 정량적인 특성을 파악하기 위하여 인천 연안 지역, 포항의 영일만을 포함한 형산강 지역 그리고 부산 연안 지역에서 시료를 채취하였다. 또한 강화도와 세어도에서 고정관측도 하였다. 연안수의 총유기탄소(TOC)와 염분과의 상관 관계 및 화학적 산소요구량(COD)과 염분과의 상관 관계를 이용하여 추정한 하천에서 연안역으로 유입되는 총유기탄소의 riverine end-member 값은 5.32 mg C/l, 화학적 산소요구량의 riverine end-member 값은 8.87 mg $O_2$/1로 나타났다 고온 촉매 산화(HTCO)방법을 이용하여 측정한 총유기탄소와 화학적 산소요구량을 비교한 결과 화학적 산소요구량은 총유기탄소의 약 47%를 반영하는 것으로 나타났다. 총유기탄소와 화학적 산소요구량에 대한 상관 관계식은 COD(mgO$_2$,/1)=0.61$\times$TOC(mg C/l)-0.03,($R^2$=0.66)으로 이 관계식을 이용하면 기존에 보고된 화학적 산소요구량으로 총유기탄소를 추정하는데 활용할 수 있을 것으로 판단된다.

• Carbon letters
• /
• 제4권4호
• /
• pp.180-184
• /
• 2003

The role of KOH in the one-stage KOH-activation of rice straws was studied using FTIR, XPS, TGA, and DTG techniques. It was found that at the impregnation, KOH extracts to some extent the lignin component from rice straw and reacts with hydroxyl groups. On heat-treatment, the impregnated KOH facilitates intermolecular condensation reaction on one hand but retards the thermal degradation of cellulose molecules on the other hand. The oxygen-containing surface functional groups newly created by oxidation of KOH may facilitate the bulk, not controlled, consumption of carbon atoms so that the effective porosities may not be able to be developed by the one-stage activation process.

• Journal of Ecology and Environment
• /
• 제42권3호
• /
• pp.128-138
• /
• 2018

Background: This study investigated the variation of soil organic carbon in four land cover types: natural and mixed forest, cultivated land, Eucalyptus plantation and open bush land. The study was conducted in the Birr watershed of the upper Blue Nile ('Abbay') river basin. Methods: The data was subjected to a two-way of ANOVA analysis using the general linear model (GLM) procedures of SAS. Pairwise comparison method was also used to assess the mean difference of the land uses and depth levels depending on soil properties. Total of 148 soil samples were collected from two depth layers: 0-10 and 10-20 cm. Results: The results showed that overall mean soil organic carbon stock was higher under natural and mixed forest land use compared with other land use types and at all depths ($29.62{\pm}1.95Mg\;C\;ha^{-1}$), which was 36.14, 28.36, and 27.63% more than in cultivated land, open bush land, and Eucalyptus plantation, respectively. This could be due to greater inputs of vegetation and reduced decomposition of organic matter. On the other hand, the lowest soil organic carbon stock under cultivated land could be due to reduced inputs of organic matter and frequent tillage which encouraged oxidation of organic matter. Conclusions: Hence, carbon concentrations and stocks under natural and mixed forest and Eucalyptus plantation were higher than other land use types suggesting that two management strategies for improving soil conditions in the watershed: to maintain and preserve the forest in order to maintain carbon storage in the future and to recover abandoned crop land and degraded lands by establishing tree plantations to avoid overharvesting in natural forests.

• Bulletin of the Korean Chemical Society
• /
• 제18권8호
• /
• pp.814-818
• /
• 1997

The chemical waste treatment, APEG (alkali/polyethylene glycol) process has been shown to be effective for the dechlorination of PCBs in transformer oil. Considerable amount of PCBs, however, still remains in the waste exceeding the 25-50 ppm limit set by regulatory agency. A new thermal regeneration technology has been developed in our laboratory for disposal of hazardous organic wastes. Due to the limited oxidation of carbon surface through the reverse movement of flame front to oxidant flow, this technology was termed counterflow oxidative system (COS). Specially, the oxidant flow in the COS process is a principal parameter which determines the optimum conditions regarding acceptable removal and destruction efficiency of adsorbed organic wastes at minimal carbon loss. The COS process, under optimum conditions, was found to be very effective and the removal and destruction efficiency of 99.99% or better was obtained for residual PCBs in the waste while bulk (≥90%) of carbon was recovered. Any toxic formation of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzo furans (PCDFs) were not detected in the regenerated carbon and impinger traps. The results of surface area measurement showed that the adsorptive property of regenerated carbon is mostly reclaimed during the COS process.

• 폴리머
• /
• 제37권1호
• /
• pp.61-65
• /
• 2013

본 실험에서는, 양극산화 처리된 탄소섬유의 표면변화가 탄소섬유강화 복합재료의 기계적 계면특성을 통하여 살펴보았다. 양극산화 처리된 탄소섬유의 표면특성은 FTIR, XPS, 그리고 SEM을 통하여 알아보았다. 복합재료의 기계적 계면특성은 층간전단강도(interlarminar shear strength; ILSS)와 임계세기인자(critical stress intensity factor; $K_{IC}$) 그리고 임계변형속도에너지(critical strain energy release rate; $G_{IC}$)를 통하여 고찰하였다. 실험결과 양극산화에 의한 각각의 표면 처리된 탄소섬유는 표면특성의 변화를 가져오며, 복합재료의 ILSS, $K_{IC}$, 그리고 $G_{IC}$같은 기계적 계면특성은 탄소섬유의 양극산화를 통하여 향상되어진다. 전해질이 20% 황산/질산(3/1)일 때 다른 전해질보다 기계적 물성의 가장 큰 향상을 보였다. 이는 양극산화로 탄소섬유와 매트릭스 사이의 계면결합력의 향상때문이라 판단된다.

• Ocean and Polar Research
• /
• 제32권3호
• /
• pp.291-297
• /
• 2010

In the summer of 2008 (August 4-14), vertical and horizontal distributions of inorganic nutrients and dissolved organic carbon (DOC) were measured in the southwestern East Sea. Concentrations of DOC were determined for the first time in the southwestern East Sea using the high-temperature combustion oxidation (HTCO) method, and results were compared with those measured by another laboratory. Concentrations of DOC ranged from 58 to 104 ${\mu}M$ in the upper 200 m, showing a typical decreasing pattern with depth. Generally, concentrations of DOC were relatively lower, with higher nutrient concentrations, in the upper layer of the coastal upwelling zone. Concentrations of DOC ranged from 54 to 64 ${\mu}M$ in the deep Ulleung Basin (200-1500 m), and were higher than those in the Pacific and Atlantic oceans. In association with rapid vertical ventilation of the euphotic, this difference indicates a larger accumulation of semi-labile DOC in the deep East Sea than in the major oceans. A correlation between apparent oxygen utilization (AOU) and DOC in the deep ocean of the East Sea revealed that only a small portion (<10%) of the sinking DOC, relative to the sinking particulate organic carbon (POC), contributes to microbial degradation. Our results present an important data set of DOC in the East Sea, which plays a critical role in carbon cycle modeling and sequestration.

• 한국환경보건학회지
• /
• 제37권1호
• /
• pp.64-72
• /
• 2011

This study was performed to assess the removal efficiency on nitrogen, phosphorus and organic carbon in wastewater by spatial separation and internal recycling in a modified oxidation ditch process (modified OD). The performances of the modified OD were evaluated via laboratory-scale experiments. The process was operated at hydraulic retention times of 6-48 hours and solid retention times of 17-38 days. We found that organic carbon removal efficiency increased after the modified OD operation period. T-N removal efficiency remained stable; average T-N concentration of effluent was 8.02 mg/l after modified OD operation. In contrast, T-P concentration of effluent was over 1 mg/l. Nitrogen and phosphorus removal efficiency of modified OD at HRT 12 hr were 83.1% and 74.1%, respectively. Also, maximum efficiency was found at SRTs from 20 to 30 days. T-N removal efficiency was 83.1% at a C/N ratio from 3.0 to 3.5. However, T-N removal efficiency decreased at C/N ratios over 3.5. Also, T-P removal efficiency increased with HRT at C/P ratios in the same condition. Maximum efficiency was 74.1% at a C/P ratio from 25 to 28. T-N removal efficiency was 79.2% and T-P removal efficiency was 65.3% after M4 mode operation (added to the internal recycle line connected to the anoxic reactor). The modified OD with spatial separation and internal recycling developed in this study is, therefore, believed to be an improvement for solving problems in the nutrient removal technologies.

• 한국환경농학회지
• /
• 제40권4호
• /
• pp.295-312
• /
• 2021

BACKGROUND: Global warming is one of the most pressing environmental issues which concomitantly complicates global climate change. Methane emission is a balance between methanogenesis and methane consumption, both of which are driven by microbial actions in different ecosystems producing methane, one of the major greenhouse gases. Paddy fields are major sources of anthropogenic methane emissions and could be compounded by organic fertilization. METHODS AND RESULTS: Literature reviews were conducted to give an overview of the global warming conditions and to present the relationship of carbon and methane to greenhouse gas emissions, and the need to understand the underlying processes of methane emission. A more extensive review was done from studies on methane emission in paddy fields under organic fertilization with greater emphasis on long term amendments. Changes in paddy soils due to organic fertilization include alterations of the physicochemical properties and changes in biological components. There are diverse phylogenetic groups of methanogens and methane oxidizing bacteria involved in methane emission. Also, multiple factors influence methanogenesis and methane oxidation in rice paddy fields under organic fertilization and they should be greatly considered when developing mitigating steps in methane emission in paddy fields especially under long term organic fertilization. CONCLUSION(S): This review showed that organic fertilization, particularly for long term management practices, influenced both physicochemical and biological components of the paddy fields which could ultimately affect methanogenesis, methane oxidation, and methane emission. Understanding interrelated factors affecting methane emission helps create ways to mitigate their impact on global warming and climate change.