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Habitat Fragmentation by a Levee and Its Impact on Frog Population in the Civilian Control Zone
Jaehyoung Ju,Jae Hyun Kim,Kim・Seung Ho Kim 한국습지학회 2016 한국습지학회지 Vol.18 No.2
본 연구는 민간인통제구역에 건설된 제방으로 인한 생태계 분절이 양서류 서식지에 미치는 영향을 알아보기 위해 수행되었다. 이를 위해 제방 한편에 두 논(사이트 1, 2)과 제방 옆을 지나는 수내천(사이트 3), 그리고 제방 다른 편의 관개수로가 위치한 논(사이트 4)에 대해 7개월간에 걸쳐 조사를 실시하였다. 조사 결과, 주로 논과 수변지역에 많이 서식하는참개구리(295개체), 청구개리(n=220개체), 옴개구리(124개체)가 주로 발견되었고 한국산 개구리(8개체)와 두꺼비(3개체)도 일부 확인되었다. 이 양서류들은 계절에 따른 물 공급 상황의 변화에 따라 논과 하천 지역에서 양적 변화를 보여사이트 1,2,3에서 두드러지게 나타났으나 제방 반대편의 사이트 4에서는 풍부한 수자원에도 불구하고 양적 변화가 적은것으로 나타났다. 가뭄철 수내천에 물이 말라 이 지역 개구리들이 현저히 감소했을 때에도 물이 풍부하고 거리가 비슷한제방 건너편의 사이트 4보다는 제방 같은 편의 사이트 1, 2 지역에서 다수의 개구리들의 존재가 확인되었다. We examined whether an artificial levee constructed on prime amphibian habitat influences fragmentation. Four different sites on both sides of a levee in the Civilian Control Zone(CCZ) were probed. Sites 1 and 2 are rice paddies on one side of the levee, and Site 3 is the stream that locates in the same side. All the three sites have water conditions of seasonal variance. On the other side, Site 4 consists of rice paddies with a stable condition of water supply, irrigated through a canal. The research sites were frequented and the frog populations were closely monitored. The investigation identified five species. Pelophylax nigromaculatus was the most frequent (n=295), followed by Hyla japonica (n=220) and Glandirana rugosa (n=124). Three Bufo gargarizans and eight Rana coreana were also found. The amphibians, however, were found to relocate themselves according to water condition to rice paddies or stream only within one side of the levee. Despite having ample sources of water and foods, Site 4 lacked large populations of frogs, even when droughts came. Both the species dominance index and the richness index indicated a more favorable living condition of the one side of the levee (Sites 1 and 2) over the other.
Seo, Young-ju,Park, Seongmin,Kang, Hyery,Ahn, Yun-Ho,Lim, Dongwook,Kim, Se-Joon,Lee, Jaehyoung,Lee, Joo Yong,Ahn, Taewoong,Seo, Yongwon,Lee, Huen Elsevier 2016 APPLIED ENERGY Vol.178 No.-
<P>A replacement technique has been regarded as a promising strategy for both CH4 exploitation from gas hydrates and CO2 sequestration into deep-ocean reservoirs. Most research has been focused on replacement reactions that occur in sI hydrates due to their prevalence in natural gas hydrates. However, sII hydrates in nature have been also discovered in some regions, and the replacement mechanism in sII hydrates significantly differs from that in sI hydrates. In this study, we have intensively investigated the replacement reaction of sII (C3H8 + CH4) hydrate by externally injecting CO2/N-2 (50:50) gas mixture with a primary focus on powder X-ray diffraction, Raman spectroscopy, NMR spectroscopy, and gas chromatography analyses. In particular, it was firstly confirmed that there was no structural transformation during the replacement of C3H8 + CH4 hydrate with CO2/N-2 gas injection, indicating that sll hydrate decomposition followed by sI hydrate formation did not occur. Furthermore, the cage-specific replacement pattern of the C3H8 + CH4 hydrate revealed that CH4 replacement with N-2 in the small cages of slI was more significant than C3H8 replacement with CO2 in the large cages of sII. The total extent of the replacement for the C3H8 + CH4 hydrate was cross-checked by NMR and GC analyses and found to be approximately 54%. Compared to the replacement for CH4 hydrate with CO2/N-2 gas, the lower extent of the replacement for the C3H8 + CH4 hydrate with CO2/N-2 gas was attributable to the persistent presence of C3H8 in the large cages and the lower content of N-2 in the feed gas. The structural sustainability and cage-specific replacement observed in the C3H8 + CH4 hydrate with external CO2/N-2 gas will have significant implications for suggesting target gas hydrate reservoirs and understanding the precise nature of guest exchange in gas hydrates for both safe natural gas production and long-term CO2 sequestration. (C) 2016 Elsevier Ltd. All rights reserved.</P>
Lim, Dongwook,Ro, Hyeyoon,Seo, Young-ju,Lee, Joo Yong,Lee, Jaehyoung,Kim, Se-Joon,Park, Youngjune,Lee, Huen American Chemical Society 2017 ENERGY AND FUELS Vol.31 No.1
<P>Natural gas hydrates, known to exist in both continental margins and permafrost regions, have received tremendous attention, owing to their potential use as an unconventional natural gas resource. Among the options to develop natural gas hydrates, a gas exchange method using an external CO2 or N-2/CO2 mixture is considered one of the most promising technologies because (i) the process can prevent structural destruction of the gas hydrate deposits by swapping CO, or N-2/CO2 for CH4 molecules and (ii) injected CO2, a global warming gas, can be sequestered and locked away through the formation of thermodynamically stable CO, or N-2/CO2 hydrate. During and after N-2/CO2 injection, however, the progress of gas exchange and the stability of the mixed CH4/N-2/CO2 hydrate must be monitored. In this study, the electrical resistivity of CH4 hydrate before, during, and after N-2/CO2 swapping was investigated using a lab-constructed tube-type reactor system for in situ electrical resistance measurement. The natural environment of a gas-hydrate-bearing sediment was simulated by forming CH4 hydrate in the pore spaces of glass beads, and its electrical properties were examined. Finally, changes in electrical resistivity were used to interpret CH4 recovery yields, while the guest composition of the gas hydrate was simultaneously analyzed by gas chromatography.</P>
Lee, Yohan,Choi, Wonjung,Seo, Young-ju,Lee, Joo Yong,Lee, Jaehyoung,Seo, Yongwon Elsevier 2018 APPLIED ENERGY Vol.228 No.-
<P><B>Abstract</B></P> <P>This study investigated a structural transition induced by cage-dependent guest exchange in the CH<SUB>4</SUB> + C<SUB>3</SUB>H<SUB>8</SUB> hydrate with CO<SUB>2</SUB> injection for CH<SUB>4</SUB> recovery and CO<SUB>2</SUB> sequestration. The influence of the CO<SUB>2</SUB> replacement on the crystalline structure of initial CH<SUB>4</SUB> + C<SUB>3</SUB>H<SUB>8</SUB> hydrates and the cage-dependent distribution of guest molecules were quantitatively investigated using powder X-ray diffraction, <SUP>13</SUP>C nuclear magnetic resonance spectroscopy, and gas chromatography. The quantitative analyses demonstrated that the CO<SUB>2</SUB> occupation caused the depletion of C<SUB>3</SUB>H<SUB>8</SUB> molecules in the large 5<SUP>12</SUP>6<SUP>4</SUP> cages of structure II hydrates, thereby resulting in the subsequent transformation into CO<SUB>2</SUB>-rich sI hydrates and the coexistence of structure I and structure II hydrates after the replacement. The guest-exchange behavior observed from time-dependent Raman spectra indicated that the replacement rate was increased with an increase in pressure of injected CO<SUB>2</SUB> and that the extent of the replacement was enhanced at higher pressure of injected CO<SUB>2</SUB>. Overall experimental evidence of the partial structural-transition replacement suggests that CO<SUB>2</SUB> molecules first occupied structure II hydrates predominantly with the rapid guest exchange at the surface and that the initial structure II hydrates were subsequently converted to the CO<SUB>2</SUB>-rich structure I hydrates from the surface to the inner side. Precise identification of the mechanism responsible for the partial structural transition occurring in the CH<SUB>4</SUB> + C<SUB>3</SUB>H<SUB>8</SUB> - CO<SUB>2</SUB> replacement will be very helpful in developing a strategy for actual CO<SUB>2</SUB> injection into structure II gas hydrate reservoirs for energy recovery and CO<SUB>2</SUB> sequestration.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The guest exchange behavior during replacement was quantitatively investigated. </LI> <LI> The CO<SUB>2</SUB> occupation induced the depletion of C<SUB>3</SUB>H<SUB>8</SUB> in the large 5<SUP>12</SUP>6<SUP>4</SUP> cages of sII. </LI> <LI> The partial structural transition occurred in the CH<SUB>4</SUB> + C<SUB>3</SUB>H<SUB>8</SUB> - CO<SUB>2</SUB> replacement. </LI> <LI> The replacement was more significant at higher pressure of injected CO<SUB>2</SUB>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>