中国稻田甲烷产生和排放研究 Ⅱ.模式研究和减排措施     

任万辉  许黎  王振会  M.A.K.Khalil  R.A.Rasmussen 《气象》2004,30(7):3-7

主要介绍了近 2 0年来稻田甲烷排放的模式研究和排放量的估算以及减少稻田甲烷排放的措施。数值模式是估算稻田甲烷排放量的一条有效途径 ,模式的研究现在正处于发展阶段。介绍了几个主要的模型 ,既有物理过程模型也有经验模型。年排放量的估算范围为 6 79～ 4 1 4Tg ,随着技术的发展和大量实验的进行估算值的精度正得到不断的提高。减排措施是减少稻田甲烷排放的必要手段 ,但是目前的减排技术均处于研究阶段 ,应用还不成熟  相似文献   

发射光谱载体蒸馏法测定地质样品中微量硼铍锡银   总被引：2，自引：2，他引：2  

李滦宁  赵淑杰  王烨 《岩矿测试》2004,23(1):30-32

选择了适合的缓冲剂,利用载体蒸馏法将被测元素与基体元素分离,使Be转变为易挥发的氟化物与B、Sn、Ag同时蒸发;降低了谱线背景及元素检出限;加入内标元素Au、Bi,提高了方法的准确度和精密度;采用普通 3mm×3mm×0.7mm杯型电极,装样量少,操作简单。方法检出限(wB/10-6)分别可达B1.5、Be0.3、Sn0.8、Ag0.02;准确度(Δlog C)基本在-0.05～0.05,精密度(RSD,n=8)为2.9%～17%。  相似文献   

Submillimeter-wave and observations of the event on 28 November, 2001     

G. Cristiani  G. Martínez  C.H. Mandrini  C.G. Gimnez de Castro  M.G. Rovira  P. Kaufmann  H. Levato 《Journal of Atmospheric and Solar》2005,67(17-18):1744

We present a detailed study of a 1B/M6.9 impulsive flare combining high time resolution (1 ms) and instantaneous emission source localization observations at submillimeter frequencies (212 GHz), obtained with the solar submillimeter telescope (SST), and Hα data from the Hα solar telescope for argentina (HASTA). The flare, starting at 16:34 UT, occurred in active region (AR) 9715 (NOAA number) on November 28, 2001, and was followed by an Hα surge. We complement our data with magnetograms from the Michelson Doppler Imager (SOHO/MDI). SST observed a short impulsive burst at 212 GHz, presenting a weak bulk emission (of about 90 sfu) composed of a few shorter duration structures. The integrated Hα and the 212 GHz light curves present a remarkable agreement during the impulsive phase of the event. The delay between both curves stays below 12 s (the time resolution of the Hα telescope). The flare as well as the surge are linked to new flux emergence very close to the main AR bipole. Taking into account the AR magnetic field evolution, we infer that magnetic field reconnection, occurring at low coronal levels, could have been at the origin of the flare; while in the case of surge this would happen at the chromospheric level.  相似文献   

Experimental study on soil CO2 emission in the alpine grassland ecosystem on Tibetan Plateau   总被引：3，自引：1，他引：3  

ZHANG Xianzhou  SHI Peili  Liu Yunfen  OUYANG Hua 《中国科学D辑(英文版)》2005,48(Z1)

The Tibetan Plateau, the Roof of the World, is the highest plateau with a mean elevation of 4000 m. It is characterized by high levels of solar radiation, low air temperature and low air pressure compared to other regions around the world. The alpine grassland, a typical ecosystem in the Tibetan Plateau, is distributed across regions over the elevation of 4500 m. Few studies for carbon flux in alpine grassland on the Tibetan Plateau were conducted due to rigorous natural conditions. A study of soil respiration under alpine grassland ecosystem on the Tibetan Plateau from October 1999 to October 2001 was conducted at Pangkog County, Tibetan Plateau (31.23°N, 90.01°E, elevation 4800 m). The measurements were taken using a static closed chamber technique, usually every two weeks during the summer and at other times at monthly intervals. The obvious diurnal variation of CO2 emissions from soil with higher emission during daytime and lower emission during nighttime was discovered. Diurnal CO2 flux fluctuated from minimum at 05:00 to maximum at 14:00 in local time. Seasonal CO2 fluxes increased in summer and decreased in winter, representing a great variation of seasonal soil respiration. The mean soil CO2 fluxes in the alpine grassland ecosystem were 21.39 mgCO2 · m-2 · h-1, with an average annual amount of soil respiration of 187.46 gCO2 · m-2 · a-1. Net ecosystem productivity is also estimated, which indicated that the alpine grassland ecosystem is a carbon sink.  相似文献   

Study of statistically correcting model CMAQ-MOS for forecasting regional air quality     

XU Jianming  XU Xiangde  LIU Yu  DING Guoan  CHEN Huailiang  HU Jiangkai  ZHANG Jianchun  WU Hao  LI Weiliang  HE Jinhai  YANG Yuanqin  WANG Jiahe 《中国科学D辑(英文版)》2005,48(Z2)

Based on analysis of the air pollution observational data at 8 observation sites in Beijing including outer suburbs during the period from September 2004 to March 2005, this paper reveals synchronal and in-phase characteristics in the spatial and temporal variation of air pollutants on a city-proper scale at deferent sites; describes seasonal differences of the pollutant emission influence between the heating and non-heating periods, also significantly local differences of the pollutant emission influence between the urban district and outer suburbs, i.e. the spatial and temporal distribution of air pollutant is closely related with that of the pollutant emission intensity. This study shows that due to complexity of the spatial and temporal distribution of pollution emission sources, the new generation Community Multi-scale Air Quality (CMAQ) model developed by the EPA of USA produced forecasts, as other models did, with a systematic error of significantly lower than observations, albeit the model has better capability than previous models had in predicting the spatial distribution and variation tendency of multi-sort pollutants. The reason might be that the CMAQ adopts average amount of pollutant emission inventory, so that the model is difficult to objectively and finely describe the distribution and variation of pollution emission sources intensity on different spatial and temporal scales in the areas, in which the pollution is to be forecast. In order to correct the systematic prediction error resulting from the average pollutant emission inventory in CMAQ, this study proposes a new way of combining dynamics and statistics and establishes a statistically correcting model CMAQ-MOS for forecasts of regional air quality by utilizing the relationship of CMAQ outputs with corresponding observations, and tests the forecast capability. The investigation of experiments presents that CMAQ-MOS reduces the systematic errors of CMAQ because of the uncertainty of pollution emission inventory and improves the forecast level of air quality. Also this work employed a way of combining point and area forecasting, i.e. taking the products of CMAQ for a center site to forecast air pollution for other sites in vicinity with the scheme of model products "reanalysis" and average over the "area".  相似文献   

Global methane emission through mud volcanoes and its past and present impact on the Earth’s climate—a comment     

Alexei V. Milkov  Giuseppe Etiope 《International Journal of Earth Sciences》2005,94(3):490-492

  相似文献   

Localization of mining-induced horizontal fractures along rock layer interfaces in overburden: field measurements and prediction   总被引：3，自引：0，他引：3  

V. Palchik 《Environmental Geology》2005,48(1):68-80

The locations of mining-induced horizontal fractures along rock interfaces in the overburden of Donetsk Coal Basin were identified using an original experimental device. The device traps methane from horizontal fracture zone (100–fold coal seam thickness) over an active longwall mining excavation. Presence or absence of horizontal fractures along rock layer interfaces is correlated with physical characteristics of the overburden, such as thickness, uniaxial compressive strength of overburden rock layers, location of rock layer interfaces and thickness of extracted coal seams. As a result, a combined criterion based on these physical characteristics is proposed to predict the presence of overburden horizontal fracturing in coal mine operations.  相似文献   

On Tension Failure of 2-D Rock Specimens and Associated Acoustic Emission     

L. G. Tham  H. Liu  C. A. Tang  P. K. K. Lee  Y. Tsui 《Rock Mechanics and Rock Engineering》2005,38(1):1-19

Summary To understand the failure mechanism of quasi-brittle materials like rock under tensile stress, observations on the failure process of granite and marble plate specimens under tension are summarized and presented. Micro- and macro-failure properties of rock plates under uniaxial tension have been characterized by using an acoustic emission technique. Acoustic emission signals associated with micro-fractures are captured to locate the sources. An algorithm based on arrival time difference is developed for this purpose. The results reveal clearly the failure processes of rock which include initiation, nucleation and propagation of micro-fractures when the axial stress is close to the peak strength of rock. It is believed that the difference in heterogeneity between granite and marble specimens leads to different fracture shapes and different behaviors of associated acoustic emissions. Numerical simulation of acoustic emissions for two-dimensional tensile test is also carried out. The simulated characteristics are in good agreement with the experimental results.  相似文献   

DEM simulations of methane hydrate exploitation by thermal recovery and depressurization methods     

《Computers and Geotechnics》2016

Methane hydrate (MH, also called fiery ice) exists in forms of pore filling, cementing and load-bearing skeleton in the methane hydrate bearing sediment (MHBS) and affects its mechanical behavior greatly. To study the changes of macro-scale and micro-scale mechanical behaviors of MHBS during exploitation by thermal recovery and depressurization methods, a novel 2D thermo-hydro-mechanical bonded contact model was proposed and implemented into a platform of distinct element method (DEM), PFC2D. MHBS samples were first biaxially compressed to different deviator stress levels to model different in-situ stress conditions. With the deviator stress maintained at constant, the temperature was then raised to simulate the thermal recovery process or the pore water pressure (i.e. confining pressure for MH bond) was decreased to simulate the depressurization process. DEM simulation results showed that: during exploitation, the axial strain increased with the increase of temperature (in the thermal recovery method) or decrease of pore water pressure (in the depressurization method); sample collapsed during MH dissociation if the deviator stress applied was larger than the compression strength of a pure host sand sample; sample experienced volume contraction but its void ratio was slightly larger than the pure host sand sample at the same axial strain throughout the test. By comparison with the laboratory test results, the new model was validated to be capable of reproducing the exploitation process by thermal recovery and depressurization methods. In addition, some micro-scale parameters, such as contact distribution, bond distribution, and averaged pure rotation rate, were also analyzed to investigate their relationships with the macroscopic responses.  相似文献   

基于敏感源分析的动态大气污染排放方案模拟   总被引：2，自引：2，他引：0       下载免费PDF全文

徐敬  张小玲  蔡旭晖  赵秀娟  苏捷  张自银  温维 《应用气象学报》2016,27(6):654-665

选取2014年11月6—11日一次典型污染过程,以北京城区为重点关注的目标区域,基于印痕分析技术判别对该区域影响较大的敏感源区,设计重点区域减排试验和敏感源区逐日动态减排试验,利用区域化学传输模式WRF-Chem进行模拟对比。结果显示:上述两种方案对源强较高的减排当地PM_2.5浓度降低均有明显的改善作用,且在传输作用下会辐射影响到下游地区;但仅就目标区域而言,敏感源区减排方案的减排效率要远远高于重点区域减排方案。为了验证基于敏感源分析的动态减排方法的适用性,进一步开展了不同季节以及不同背景浓度的个例模拟。结果表明:基于敏感源区分析结果制定动态逐日减排措施,可降低削减成本、提高减排效率,以达到最具经济环境效益的减排效果。  相似文献