Tropospheric methane in the mid-latitudes of the Southern Hemisphere     

P. J. Fraser  M. A. K. Khalil  R. A. Rasmussen  L. P. Steele 《Journal of Atmospheric Chemistry》1984,1(2):125-135

Results of more than 800 new measurements of methane (CH₄) concentrations in the Southern Hemisphere troposphere (34–41° S, 130–150° E) are reported. These were obtained between September 1980 and March 1983 from the surface at Cape Grim, Tasmania, through the middle (3.5–5.5 km) to the upper troposphere (7–10 km). The concentration of CH₄ increased throughout the entire troposphere over the measurement period, adding further support to the view that CH₄ concentrations are currently increasing on a global scale. For data averaged vertically through the troposphere the rate of increase found was 20 ppbv/yr or 1.3%/yr at December 1981. In the surface CH₄ data a seasonal cycle with a peak to peak amplitude of approximately 28 ppbv is seen, with the minimum concentration occurring in March and the maximum in September–October. A cycle with the same phase as that seen at the surface, but with a significantly decreased amplitude, is apparent in the mid troposphere but no cycle is detected in the upper tropospheric data. The phase and amplitude of the cycle are qualitatively in agreement with the concept that the major sink for methane is oxidation by hydroxyl radicals. Also presented is evidence of a positive vertical gradient in methane, with a suggestion that the magnitude of this gradient has changed over the period of measurements.  相似文献   

The global distribution of methane in the troposphere   总被引：6，自引：0，他引：6  

L. P. Steele  P. J. Fraser  R. A. Rasmussen  M. A. K. Khalil  T. J. Conway  A. J. Crawford  R. H. Gammon  K. A. Masarie  K. W. Thoning 《Journal of Atmospheric Chemistry》1987,5(2):125-171

Methane has been measured in air samples collected at approximately weekly intervals at 23 globally distributed sites in the NOAA/GMCC cooperative flask sampling network. Sites range in latitude from 90° S to 76° N, and at most of these we report 2 years of data beginning in early 1983. All measurements have been made by gas chromatography with a flame ionization detector at the NOAA/GMCC laboratory in Boulder, Colorado. All air samples have been referenced to a single secondary standard of methane-in-air, ensuring a high degree of internal consistency in the data. The precision of measurements is estimated from replicate determinations on each sample as 0.2%. The latitudinal distribution of methane and the seasonal variation of this distribution in the marine boundary layer has been defined in great detail, including a remarkable uniformity in background levels of methane in the Southern Hemisphere. We report for the first time the observation of a complete seasonal cycle of methane at the South Pole. A significant vertical gradient is observed between a sea level and a high altitude site in Hawaii. Globally averaged background concentrations in the marine boundary layer have been calculated for the 2 year-period May 1983–April 1985 inclusive, from which we find an average increase of 12.8 ppb per year, or 0.78% per year when referenced to the globally averaged concentration (1625 ppb) at the mid-point of this period. We present evidence that there has been a slowing down in the methane growth rate.Presented at the Conference on the Scientific Application of Baseline Observations of Atmospheric Composition (SABOAC), Aspendale, Australia, 7–9 November 1984.  相似文献   

Termites and global methane—another assessment     

P. J. Fraser  R. A. Rasmussen  J. W. Creffield  J. R. French  M. A. K. Khalil 《Journal of Atmospheric Chemistry》1986,4(3):295-310

New CH₄ emission data from a number of Northern and Southern Hemispheric, tropical and temperate termites, are reported, which indicate that the annual global CH₄ source due to termites is probably less than 15 Tg. The major uncertainties in this estimate are identified and found to be substantial. Nevertheless, our results suggest that termites probably account for less than 5% of global CH₄ emissions.  相似文献   

广州地区稻田甲烷排放及中国稻田甲烷排放的空间变化   总被引：13，自引：0，他引：13  

沈壬兴  卢巨祥 《地球科学进展》1995,10(4):387-392

１９９３年在广州地区采用中国科学院大气物理研究所研制的自动采集和分析系统测量了稻田甲烷的排放率，首次获得了占我国２０－２５％左右水稻收获面积的华南地区稻田甲烷排放特征值。从而宏观地使我国五个主要水稻生态区的甲烷排放率都有了实测资料。稻田甲烷排放率的季节变化主要与气温及灌溉水状态的变化的较大关系，日变化规律以下午出现极大为主。本实验田的甲烷排放率低。  相似文献   

Automated in-situ monitoring of atmospheric non-methane hydrocarbon concentrations and gradients     

A. H. Goldstein  B. C. Daube  J. W. Munger  S. C. Wofsy 《Journal of Atmospheric Chemistry》1995,21(1):43-59

A fully automated system measuring C2–C6 hydrocarbon concentrations and vertical gradients was installed at Harvard Forest in Petersham, Massachusetts, using a gas chromatograph with dual flame ionization detectors and cryogenic sample preconcentration. Measurements were made simultaneously at two heights above the forest canopy at forty five minute intervals, continuously from July 1992 to the present. Data for concentration gradients were combined with CO₂ flux measured by eddy correlation to determine the rates of production of biogenic hydrocarbons by the forest.  相似文献   

Estimates of monoterpene and isoprene emissions from the forests in Switzerland   总被引：1，自引：0，他引：1  

S. Andreani-aksoyoglu  J. Keller 《Journal of Atmospheric Chemistry》1995,20(1):71-87

Emission rates of biogenic volatile organic compounds emitted by the forests were estimated for five geographical regions as well as for all Switzerland. Monoterpene and isoprene emissions rates were calculated for each main tree species separately using the relevant parameters such as temperature, light intensity and leaf biomass density. Biogenic emissions from the forests were found to be about 23% of the total annual VOC emissions (anthropogenic and biogenic) in Switzerland. The highest emissions are in July and lowest in January. Calculations showed that the coniferous trees are the main sources of the biogenic emissions. The major contribution comes from the Norway spruce (picea abies) forests due to their abundance and high leaf biomass density. Although broad-leaved forests cover 27% of all the forests in Switzerland, their contribution to the biogenic emissions is only 3%. Monoterpenes are the main species emitted, whereas only 3% is released as isoprene. The highest emission rates of biogenic VOC are estimated to be in the region of the Alps which has the largest forest coverage in Switzerland and the major part of these forests consists of Norway spruce. The total annual biogenic VOC emission rate of 87 ktonnes y^–1 coming from the forests is significantly higher than those from other studies where calculations were carried out by classifying the forests as deciduous and coniferous. The difference is attributed to the high leaf biomass densities of Norway spruce and fir (abies alba) trees which have a strong effect on the results when speciation of trees is taken into account. Besides the annual rate, emission rates were calculated for a specific period during July 4–6, 1991 when a photochemical smog episode was investigated in the Swiss field experiment POLLUMET. Emission rates estimated for that period agree well with those calculated for July using the average temperatures over the last 10 years.  相似文献   

粘滑失稳及其物理场时空分布的实验研究   总被引：6，自引：3，他引：6  

邓志辉  马胜利 《地震地质》1995,17(4):305-310

摩擦滑动的物理场实验研究表明：（１）能量空间分布的差异是失稳的重要条件，单发型大事件常发生于高能量向低能量的突变带或高能量背景区内的相对低能量区；（２）单发型大事件的孕育过程常常经历若干个能量输入输出循环，产生多个前兆阶段，并在失稳前源区常有一个弱化过程。小震或群发型事件失稳前常常只有一个能量积累与强化的过程，失稳前兆阶段性反映较差；（３）粘滑失稳时断层的位错与声发射的大小未见明显关系  相似文献   

电感耦合等离子体发射光谱法测定高铁三水铝土矿中的主量和次量元素     

黄肇敏  崔萍萍  周素莲 《矿产与地质》2007,21(4):476-478

采用电感耦合等离子体发射光谱法,同时测定高铁三水铝土矿中的Si、Fe、Al、Ti、Mn、V、As、P等元素。对影响其光谱测量的各种因素进行了较为详细的研究,确定了最佳的试验测定条件。结果表明,该方法的检出限为0.0012-0.061μg/mL,回收率为95.4%-107.4%,主量元素相对标准偏差在1%-3%之间,次量元素相对标准偏差在2%-6%之间。该方法准确、快速、简便,应用于高铁三水铝土矿的测定,结果令人满意。  相似文献   

Raman spectra of methane hydrate up to 86 GPa     

Shin-Ichi Machida  Hisako Hirai  Taro Kawamura  Yoshitaka Yamamoto  Takehiko Yagi 《Physics and Chemistry of Minerals》2007,34(1):31-35

High-pressure Raman studies of methane hydrate were performed using a diamond anvil cell in the pressure range of 0.1–86 GPa at room temperature. Raman spectra of the methane molecules revealed that new softened intramolecular vibration mode of ν ₁ appeared at 17 GPa and that the splitting of vibration mode of ν ₃ occurred at 15 GPa. The appearance of these two modes indicates that an intermolecular attractive interaction increases between the methane molecules and the host water molecules and between the neighboring methane molecules. These interactions might result in the exceptional stability of a high-pressure structure, a filled ice Ih structure (FIIhS) for methane hydrate, up to 40 GPa. At 40 GPa, a clear change in the slope of the Raman shift versus pressure occurred, and above 40 GPa the Raman shift of the vibration modes increased monotonously up to 86 GPa. A previous XRD study showed that the FIIhS transformed into another new high-pressure structure at 40 GPa. The change in the Raman spectra at 40 GPa may be induced by the transition of the structure.  相似文献   

湿地甲烷氧化测定方法及主要控制因子研究综述     

王维奇  曾从盛  仝川 《福建地理》2007,(3)

湿地甲烷氧化是控制湿地甲烷通量的重要因子.本文对湿地甲烷氧化的测定方法与主要控制因子进行了综述.湿地甲烷氧化的测定方法主要包括未添加甲烷氧化抑制剂培养法和添加甲烷氧化抑制剂培养法.湿地甲烷氧化是诸多因子综合作用的结果,控制湿地甲烷氧化的因子包括湿地生态系统类型、温度、土壤湿度、底物、pH值等.比较而言,底物的浓度(甲烷和氧化性物质)以及土壤湿度是更为重要的环境因子.  相似文献