初冬季节青藏高原清水河地区甲烷排放率变化(英)     

JIN Hui-Jun  CHENG Guo-Dong 《冰川冻土》1998,(4)

As the globally largest area covered by high altitudinal permafrost, the Qinghai-Tibet Plateau may contribute substantially to atmospheric CH4 budget when global warming. Preliminary observations on CH4 emission at Qingshuihe from November 5 to 14, 1995 show that alpine grassland may be a small source for atmospheric CH4 during early winter. The emission rates of CH4 from moist grassland surface varied from-16. 1 to 23. 9 μg. m-2h-1, with an average of 1. 82 μg. m-2h-1. Emission rates of CH4 from water surface of Qingshuihe River were from -21. 0 to 37. 1 μg. m-2h-1, with an average of 1. 56 μg. m-2h-1. The emission rates of CH at 30 to 200 cm in depth ranged from-69. 0 to 36. 0 μg. m-2h-1, with the average rate at these depths varying from -2. 15 to 2. 04 μg' m-2h-1. The mean emission rates of CH4 in the active layer and permafrost indicate the lower part of active layer tends to release CH4, CH4 is absorbed at low rates in the middle section and in the vicinity of permafrost table, and net fluxes of CH4 is emitted from the soils in the upper part. During the observation periods, the methane concentrations in static chambers and emission rates of grassland and water surface displayed noticeable diurnal variations. The water/ice content may play important role in the spatial variations of methane emission rates. The emission rates of methane is weakly correlated with the ground temperatures at sampling depths and air temperatures. The observed emission rates of methane from the comparatively dry and sandy grassland soils are quite low compared with that observed in the permafrost regions in the high latitudes.  相似文献   

探头不同耦合方式AE法岩石应力测量效果比较     

丁原辰 《地球物理学进展》1998,13(3):67-73

以凯瑟效应测量岩石试样先存应力,声发射探头与试样的耦合是不共重要环节,国内外学者采用的耦合方法,归结起来主要是面耦合与线耦合两种方式,作者以同一试样作了这两种耦合方法的对比实验,证实地耦合的测量效果优于面耦合,作者指出：使用圆柱状试样不仅制作简便,节省制作费用,而且由于探头与试样作线耦合获得更高的测量精度。  相似文献   

Gas emission prediction and recovery in underground coal mines   总被引：2，自引：0，他引：2  

Leszek W. Lunarzewski 《International Journal of Coal Geology》1998,35(1-4)

Strata gas can be released and captured from non-active and active gas resources either from virgin or relaxed strata, both prior to and when mining activities take place. The high and irregular gas emissions associated with high production longwall mining have provided a need to optimise the methods used to predict these gas levels and the ventilation requirements for gas dilution. A forecast of gas emissions during development drivage and longwall mining indicated possible gas and ventilation problems requiring the introduction of various gas drainage techniques and in maintaining the necessary air quantities in ventilation systems to satisfy the statutory gas limitations for various coal production rates. Although there are sound principles used in world-recognised methods of gas emission prediction, a new approach developed from long-term practical experience in underground gassy coal mine practices and gas-rock mechanics studies appear most suitable for local conditions and mining systems in use. The Lunagas ‘Floorgas' and ‘Roofgas' geomechanical and gas emission models offer an effective solution to these problems. Both programs are the most advanced engineering, numerical tools available to calculate gas source contributions to total gassiness and improve the accuracy and quality of gas control, gas capture technologies and ventilation system design.  相似文献   

B0712+472: a new radio four-image gravitational lens     

N. Jackson  S. Nair  I. W. A. Browne  P. N. Wilkinson  T. W. B. Muxlow  A. G. de Bruyn  L. Koopmans  M. Bremer  I. Snellen  G. K. Miley  R. T. Schilizzi  S. Myers  C. D. Fassnacht  D. S. Womble  A. C. S. Readhead  R. D. Blandford  & T. J. Pearson 《Monthly notices of the Royal Astronomical Society》1998,296(3):483-490

A new four-image gravitational lens system, B0712+472, has been discovered during the Cosmic Lens All-Sky Survey. This system consists of four flat-spectrum radio images that are also seen on a Hubble Space Telescope ( HST ) image, together with the lensing galaxy. We present MERLIN, VLA and VLBA maps and WHT spectra of the system as well as the HST images. The light distribution of the lensing galaxy is highly elongated and so too is the mass distribution deduced from modelling. We suggest a redshift of ∼1.33 for the lensed object; the lens redshift will require further investigation. The discovery of this new system further increases the ratio of four-image to two-image lens systems currently known, exacerbating problems of required ellipticity of matter distributions in lensing galaxies.  相似文献   

A new look at the isotropy of narrow-line emission in extragalactic radio sources     

Chris Simpson 《Monthly notices of the Royal Astronomical Society》1998,297(2):L39-L43

We undertake a quantitative investigation, using Monte Carlo simulations, of the amount by which quasars are expected to exceed radio galaxies in optical luminosity in the context of the 'receding torus' model. We compare these simulations with the known behaviour of the [O  III ] λ5007 and [O  II ] λ3727 emission lines and conclude that [O  III ] is the better indicator of the strength of the underlying non-stellar continuum.  相似文献   

Sources and sinks of atmospheric methane   总被引：7，自引：0，他引：7  

D. H. Ehhalt  U. Schmidt 《Pure and Applied Geophysics》1978,116(2-3):452-464

In 1972 average mixing ratio of methane in the troposphere was 1.41 ppm and 1.3 ppmv for the northern and southern hemisphere, respectively, which corresponds to a total amount of 4×10¹⁵ g of CH₄ present in the atmosphere. Most is of recent biologic origin.¹⁴C analyses show that no more than 20 percent is released by fossil sources. The various ecosystems producing CH₄ are discussed and the total annual production is estimated to lie between 5.5×10¹⁴ g/yr and 11×10¹⁴ g/yr. The corresponding turnover times for atmospheric CH₄ range from 4 to 7 yrs. The destruction of CH₄ takes place mainly in the troposphere, most probably through the reaction of CH₄ + OH CH₃ + H₂O. About 10 percent of the CH₄ is destroyed in the stratosphere. The CH₄ cycle contributes on the order of 1 percent to the atmospheric carbon cycle.  相似文献   

Mitigating Agricultural Emissions of Methane   总被引：7，自引：0，他引：7  

A.R. Mosier  J.M. Duxbury  J.R. Freney  O. Heinemeyer  K. Minami  D.E. Johnson 《Climatic change》1998,40(1):39-80

Agricultural crop and animal production systems are important sources and sinks for atmospheric methane (CH4). The major CH4 sources from this sector are ruminant animals, flooded rice fields, animal waste and biomass burning which total about one third of all global emissions. This paper discusses the factors that influence CH4 production and emission from these sources and the aerobic soil sink for atmospheric CH4 and assesses the magnitude of each source. Potential methods of mitigating CH4 emissions from the major sources could lead to improved crop and animal productivity. The global impact of using the mitigation options suggested could potentially decrease agricultural CH4 emissions by about 30%.  相似文献   

Comparison of manual and automatic methods for measurement of methane emission from rice paddy fields   总被引：29，自引：0，他引：29  

Zheng Xunhu  Wang Mingxing  Wang Yuesi  Shen Renxing  Li Jing  J. Heyer M. Kogge  Li Laotu  Jin Jisheng 《大气科学进展》1998,15(4):569-579

The methane emission flux from rice paddies was simultaneously measured with automatic and manual methods in the suburban of Suzhou. Both methods were based on the static chamber/ GC-FID techniques. Detail analysis of the experimental results indicates: a) The data of methane emission measured with the automatic method is reliable. b) About 11 or 19 o’clock of local time is recommended as the optimum sampling time for the manual spot measurement of methane emission from rice paddies. The methane emission fluxes measured by manual sampling at local time other than the optimum time have to be corrected. The correction coefficient may be determined by automatic and continuous measurement. c) In order to get a more accurate result, an empirical correction factor, such as 18%, is recommended to correct the seasonally total amount of measured methane emission by enlarging the au-tomatically measured data or reducing the manually measured ones.  相似文献   

中国地区气溶胶的辐射强迫及其气候响应试验   总被引：15，自引：3，他引：12  

胡荣明  石广玉 《大气科学》1998,22(6):917-525

根据国内测定的排放因子数据和国家、部委及各省市统计年鉴公布的排放源数据,得到的中国大陆的1°×1°网格精度的SO2的排放分布,计算了中国地区人为扰动气溶胶的辐射强迫。应用近期开发的二维能量平衡模式计算了由该种气溶胶所引起的中国地区地面温度变化。模式结果表明,最大辐射强迫和最大地面温度变化都集中在中国的沿海和四川地区。最大辐射强迫达3 W/m2。  相似文献   

Evidence of the Link between Broad Emission Line Regions and Accretion Disks in Active Galactic Nuclei     

Yun Xu    Xin-Wu Cao Shanghai Astronomical Observatory  Chinese Academy of Sciences  Shanghai  Graduate School of Chinese Academy of Sciences  Beijing 《中国天文和天体物理学报》2007,7(1):63-70

1 INTRODUCTION Most bright active galactic nuclei (AGNs) exhibit broad emission lines, with full width at half maximum (FWHM ≥ 103 km s?1) (Peterson et al. 1999). Some type 1 AGNs could have very broad emission lines (FWHM≥ 20 000 km s?1). Type 2 AGNs s…  相似文献