Phase stability and kinetics of methane hydrate formation in presence of calcium and magnesium carbonate     

Ekta Chaturvedi  Krishan Patidar  Sukumar Laik 《Marine Georesources & Geotechnology》2019,37(1):57-66

The huge amount of methane hydrate deposits identified in deep marine sediments is considered as the new resource for future energy. Since carbonates are one of the major components of marine sediments, in the present study, an investigation has been made to study methane hydrate stability and kinetics in the presence of CaCO₃ and MgCO₃. Effect of the presence of carbonates on the solubility of methane in the system has also been examined as it directly affects the hydrate formation process. It has been observed that in presence of CaCO₃ and MgCO₃, the hydrate formation is inhibited. Comparative studies have also been done in the presence of artificial seawater to consider the effect of presence of different salts. Mole consumption of methane gas during hydrate formation in different carbonate samples was measured using real gas equation and found to be minimum in CaCO₃ in seawater sample due to the combined effect of the presence of CaCO₃ and different salts of seawater. An increase in nucleation and induction time was also observed demonstrating the inhibition of hydrate formation in the presence of these components. Further, the decrease in hydrate formation rate also confirmed the inhibition effect of CaCO₃ and MgCO₃ on hydrate formation.  相似文献   

Physical processes causing the formation of hypoxia off the Changjiang estuary after Typhoon Chan-hom, 2015     

GUO Yaru  RONG Zengrui  LI Bo  XU Zhao  LI Pixue  LI Xiaodan 《海洋湖沼学报（英文）》2019,(1):1-17

Severe hypoxia was observed in the submarine canyon to the east of the Changjiang estuary in July 14, 2015, two days after typhoon Chan-hom. The oxygen concentration reached as low as 2.0 mg/L and occupied a water column of about 25 m. A ROMS model was con?gured to explore the underlying physical processes causing the formation of hypoxia. Chan-hom passed through the Changjiang estuary during the neap tide. The strati?cation was completely destroyed in the shallow nearshore region when typhoon passing. However, it was maintained in the deep canyon, though the surface mixed layer was largely deepened. The residual water in the deep canyon is considered to be the possible source of the later hypoxia. After Chan-hom departure, not only the low salinity plume water spread further of fshore, but also the sea surface temperature(SST) rewarmed quickly. Both changes helped strengthen the strati?cation and facilitate the formation of hypoxia. It was found that the surface heat ?ux, especially the solar short wave radiation dominated the surface re-warming, the of fshore advection of the warmer Changjiang Diluted Water(CDW) also played a role. In addition to the residual water in the deep canyon, the Taiwan Warm Current(TWC) was found to ?ow into the deep canyon pre-and soon post-Chan-hom, which was considered to be the original source of the hypoxia water.  相似文献   

Recent satellite-derived sea ice volume flux through the Fram Strait: 2011–2015   总被引：1，自引：0，他引：1  

毕海波  王云鹤  张文峰  ZHANG Zehu  LIANG Yu  ZHANG Yi  胡文敏  付敏  黄海军 《海洋学报(英文版)》2018,37(9):107-115

The Fram Strait(FS) is the primary region of sea ice export from the Arctic Ocean and thus plays an important role in regulating the amount of sea ice and fresh water entering the North Atlantic seas. A 5 a(2011–2015) sea ice thickness record retrieved from Cryo Sat-2 observations is used to derive a sea ice volume flux via the FS. Over this period, a mean winter accumulative volume flux(WAVF) based on sea ice drift data derived from passivemicrowave measurements, which are provided by the National Snow and Ice Data Center(NSIDC) and the Institut Francais de Recherche pour d'Exploitation de la Mer(IFREMER), amounts to 1 029 km~3(NSIDC) and1 463 km~3(IFREMER), respectively. For this period, a mean monthly volume flux(area flux) difference between the estimates derived from the NSIDC and IFREMER drift data is –62 km~3 per month(–18×10~6 km~2 per month).Analysis reveals that this negative bias is mainly attributable to faster IFREMER drift speeds in comparison with slower NSIDC drift data. NSIDC-based sea ice volume flux estimates are compared with the results from the University of Bremen(UB), and the two products agree relatively well with a mean monthly bias of(5.7±45.9) km~3 per month for the period from January 2011 to August 2013. IFREMER-based volume flux is also in good agreement with previous results of the 1990 s. Compared with P1(1990/1991–1993/1994) and P2(2003/2004–2007/2008), the WAVF estimates indicate a decline of more than 600 km~3 in P3(2011/2012–2014/2015). Over the three periods, the variability and the decline in the sea ice volume flux are mainly attributable to sea ice motion changes, and second to sea ice thickness changes, and the least to sea ice concentration variations.  相似文献   

Modeling of rising methane bubbles during production leaks from the gas hydrate sites of India     

N. Vedachalam  S. Ramesh  P. Udaya Prasanth  G. A. Ramadass 《Marine Georesources & Geotechnology》2018,36(8):966-973

Natural gas hydrates is considered as a strategic unconventional clean hydrocarbon resource in the energy sector. Understanding the behavior of the rising methane gas bubbles during production leaks from the deep marine gas hydrate reservoirs well head is essential for environmental impact studies and to design environmental monitoring systems. Numerical model for quantitatively characterizing the vertical dissolution pattern of the wellhead released methane gas bubbles is analyzed for three potential gas hydrate locations in India. Simulation results indicate that the methane bubbles with diameter of 10?mm can transport methane gas till 650, 800, and 750?m from the seabed in the Krishna–Godavari(KG), Mahanadi and Andaman basins respectively. Results brought out that potential well head damage during methane hydrate production at 1050?m water depth could release up to 28?m³ of methane gas, in which 50% of the molar mass shall get dissolved within 40?m of water column from the seafloor.  相似文献   

SO2 emissions at Mt. Etna with particular reference to the period 1993–1995     

N. Bruno  T. Caltabiano  R. Romano 《Bulletin of Volcanology》1999,60(6):405-411

The variations in sulfur dioxide (SO₂) emission from the Summit Craters of Mt. Etna were determined, with particular reference to the period 1993–1995. Vehicle-based weekly measurements of SO₂ flux, using a correlation spectrometer (COSPEC), suggest new input of magma into the main feeder system of the volcano between 1993 and 1995. Minimal flux values (<1000 t/day) preceded the two eruptive events in the period 1987–1995. Only approximately 9.5% of the magma that contributed the SO₂ emission was erupted during the same period. Received: 3 November 1997 / Accepted: 21 September 1998  相似文献   

关于煤层甲烷资源量分级的思考     

刘建华  唐修义 《中国煤田地质》1999,11(3):18-21

通过对淮南煤田西部煤层甲烷资料的分析, 选择了煤炭储量的类别、煤层甲烷含量的有效测点密度和评价验证钻孔中参数的获取情况作为煤层甲烷资源量分级的综合指标, 建立了包括实证、控制、概略、远景和潜在等五个级别的煤层甲烷资源量的分级标准。  相似文献   

MATHEMATICAL MODEL OF SLUDGE SEDIMENTATION     

ZHOU Kezhao  + 《国际泥沙研究》1999,(3)

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A remote sensing model of CO2 flux for wheat and studying of regional distribution     

Renhua Zhang  Xiaomin Sun  Zhilin Zhu  Hongbo Su  Gang Chen 《中国科学D辑(英文版)》1999,42(3):325-336

A model for calculating CO₂ flux in the wheat field and an algorithm for estimating CO₂ flux in the mejonal scale were presented using the remote sensing data and supplementary micpo-met~orological data. First of all a-longertenn measurement wae carried out during winter wheat growing period in Yucheng Experimental Station udng the spectmradiometer system, the thermal infrared radiometer system, the Bowen-ratio device as well as the eddy-correlation device. Two kinds of issues concerning remote sensing and CO₂ flux can be obtained. Based on the obeervations a remote sensing model was estabilished. Then when the NOAA-AVHRR passed over the experimental area simultaneous measurements were carried out with the satellites. A regional distribution image for CO₂ flux over wheat canopy in North China (500×500 km²) was made using the supplementary ground data and NOAA-AVHRR remote sensing data which was calibrated by the synchronous observation. The sources and sinks for CO₂ fluxes in the region can be seen obviously. Project supported by the National Natural Science Foundation of China (Grant Nos. 49671058, 49890330)  相似文献   

古尔班通古特沙漠的辐射热量交换分析   总被引：29，自引：13，他引：16  

魏文寿  董光荣 《中国沙漠》1997,17(4):335-341

位于新疆准噶尔盆地的古尔班通古特沙漠是我国第二大沙漠。根据古尔班通古特沙漠的自然条件,对不同下垫面区域的太阳短波辐射和大气长波辐射热量进行了测量。结果表明:在晴天状况下,流动沙丘和固定沙丘的热量交换差异主要是由地表状况、沙层性质和气温等因素决定的。流动沙丘区反射率与长波辐射大于固定沙丘区,并且日、季变化明显。长波最大辐射值出现在午后,近似于太阳总辐射,最小值出现在日出前;沙层热通量随着深度的增加而增大,而辐射热量传输则随其深度的增加而减小,无论是流动沙层还是固定沙层,其热通量的零界面深度却基本一致(9月份),均在30~35cm之间。根据上述结果,本文还讨论了沙漠区在热量交换过程中,辐射热量差异引起的沙漠小气候效应和沙漠对区域气候的反馈作用。  相似文献   

Sensitivity analysis of sediment flux derived by laser diffraction and acoustic backscatter within a reservoir     

Stefan Haun  Laura Lizano 《国际泥沙研究》2018,33(1):18-26

A combination of two indirect methods to measure sediment flux is presented in this study to evaluate suspended sediment transport in a hydropower reservoir. The acoustic backscatter signal (ABS) from an Acoustic Doppler Current Profiler (ADCP) is therefore applied in pre-defined transects within the reservoir in combination with a Laser In-Situ Scattering Transmissometry – stream lined device (LISST-SL). The stationary LISST-SL derived suspended sediment concentration (SSC) measurements are used to calibrate the ABS. From the LISST-SL measurements a time series of SSC is obtained. This enables, in addition, a comprehensive data analysis to evaluate the influence of natural fluctuations of the SSC on the calculated sediment flux, which should be taken into account when assessing sediment transport. Furthermore SSC measurements are done with the LISST-SL close to the reservoir bed. In areas close to the bed no information regarding the ABS is available from the ADCP measurements due to the side-lobe interference. In various studies the information from the last three valid cells is used for extrapolation. However, as result of a comparison of the LISST-SL measurements with extrapolated SSC values from the ADCP measurements it can be seen that, especially in deep reservoirs, this method has to be adapted to the in-situ conditions.  相似文献