NUMERICAL SIMULATION OF METHANE EMISSIONS FROM RICE PADDY FIELDS IN THE YANGTZE DELTA OF CHINA*

A numerical simulation model is presented in this paper,which comprises the processes of crop growth,soil organic carbon decomposition,and methane emissions in agroecosystems.Simulation results show that the model can simulate the main process of methane emissions well,and the correlation coefficient between the simulated values and observed data is 0.79 with 239 samples,which passed a significance test of 0.01.The average error of methane emission simulation in whole growth period is about 15%.Numerical analysis of the model indicates that the average temperature during rice growth period has much impacts on methane emissions,and the basic trend of interannual methane emissions is similar to that of average temperature.The amount of methane emissions reduces about 34.93%,when the fertilizer is used instead of manure in single rice paddy.     

NUMERICAL SIMULATION OF ATMOSPHERIC METHANE TRENDS OVER THE LAST 150 YEARS*

A global two-dimensional chemistry model is developed to study long-term trends of CH₄ since industrial revolution.The sources of CH₄,CO and NO_x are parameterized as functions of latitude and time.With two long-term emission scenarios,long-term trends of CH₄ are simulated.The results have a good agreement with observation from ice cores.The modeled CH₄ increased from 760 ppbv in 1840 to 1611.9 ppbv in 1991, while the modeled number concentration of tropospheric OH decreased from 7.17×10⁵ cm^-3 in 1840 to 5.79×10⁵ cm^-3 in 1991.The increase of atmospheric CH₄ can be explained by the increase of emission of CH₄ and build-up because of decrease of OH radicals that remove CH₄ from the atmosphere.The model is also used to simulate the distribution of CH₄.Comparisons between the model results and observations show that the model can simulate both latitudinal distribution and seasonal variation of CH₄ well.     

REMOTE SENSING OF THE SEASONAL VARIATION IN COLUMN ABUNDANCE OF ATMOSPHERIC CH4*

Infrared solar spectra on clear days were measured automatically by an infrared solar spectrometer(ISS) with 0.4 cm^-1 resolution developed by us.A line-by line(LBL) computation method was used to calculate theoretical atmospheric absorption.In the wavelength range of 3.410-3.438 μm.the absorption is mainly due to atmospheric methane and water vapor.Columnatmospheric methane was retrieved from the recorded infrared solar spectra.The seasonal variation of column atmospheric methane in Hefei has been obtained from the measuremental data of nearly 18 months since the April of 1997.and found that it is similar to that of background data.The instruments.principles of measurement and some of results were introduced,and the results are also discussed briefly in the paper.     

日本南海海槽天然气水合物研究现状

本文介绍日本在其周围海域特别是南海海槽的海洋天然气水合物研究工作，首先介绍其研究简史，研究计划，研究队伍及早期研究成果，其次，介绍了西南海海槽天然气水合物的勘探、研究状况，然后,介绍了五年计划实施的东南海海槽地球物理勘探、钻探状况，最后指出，南海海槽的一些新资料深入的综合研究无疑会给世界水合物研究增添新的内容。     

天然气水合物的地热研究进展

天然气水合物的地热研究在以下几个方面都取得了重要进展，热流与似海底反射层的关系，水合物稳定带的研究；水合物热物理参数的确定；水合物形成过程中的热状态；热导率的应用，指出了今后水合物的地热学研究方向。     

煤层煤质和含气量的测井评价方法及其应用

根据辽河油田东部凹陷煤储层的地质特征以及实际煤岩芯分析资料和测井资料,利用回归分析方法得出了计算煤层各组分含量和煤阶的方法;通过分析煤层气特征,利用兰氏方程、吸附等温线和煤层气层中子背景值导出了煤层含气量的计算公式,并通过辽河油田东部凹陷实际煤储层测井资料的处理解释验证了方法的有效性。     

山西沁水煤层气田采收率预测

采用地质类比、等温吸附曲线及储层数值模拟 3种方法对山西沁水煤层气田主力气层———二叠系山西组 3# 煤层、石炭系太原组 15 # 煤层的煤层气采收率进行了预测 ,结果 3# 煤层的煤层气采收率为 6 2 % ,15 # 煤层的采收率为 5 5 % ,总平均采收率为 5 9%。分析对比了这 3种方法的运用条件及优缺点 ,指出煤层气采收率的预测必须采用多种方法 ,并结合具体的煤层气地质特点进行综合分析 ,才能得出合理的结论。     

低沼矿区煤层气体地化特征及其灾害性

用立体地球化学的观点和方法研究了徐州煤田“低沼矿区”的瓦斯问题可以获得“低沼矿区”煤层气体是以甲烷为主,重烃含量甚低,δ~(13)C_1偏负等特征,并指出:低沼矿区具有相对性的特点,在一定条件下,煤层仍可具一定的气体灾害性。另外,用碳同位素方法还可以判别“煤层气体的活性”,以反映煤层气体和地下水的灾害倾向性。     

Factors Affecting Methane Emission from Rice Paddies

A comparative study of rice paddies and the uncovered water field in Taoyuan(Hunan) showed that methane emission from rice-vegetated paddy fields in 1993 was different from that in 1992(I,e,lower in rates and irregular in pattern).Climate has obvious influence on methane emission .And ebullition made a considerable contribution to the total flux of methane emission from rice paddies (45%).This implies that the intensification of paddy cultivation of rice might not be,as was proposed,the main con-tributor to the observed gradual increasing of atmospheric methane.24-hour automatic measurements of atmospheric temperature,air temperature and methane concentration in the static sampling boxes revealed that temperature,in addition to fertilization and irrigation style,is one of the most important factors that control the emission of methane from rice paddies.     

农田生态系统温室气体排放研究进展

自1985年起,中国科学院大气物理研究所利用自行设计制造的自动观测仪器系统,历时十六年先后对我国四大类主要水稻产区的甲烷排放规律及其与土壤、气象条件和农业管理措施的关系进行了系统野外观测实验,并对稻田甲烷产生、转化和输送机理进行了理论研究,探讨了控制稻田甲烷排放的实用措施,建立了估算和预测稻田甲烷排放的数值模型.在甲烷排放的时空变化规律和转化率研究方面有一系列新的发现,在稻田甲烷产生率、排放率及其与环境条件的关系方面取得一系列新的成果,以充分证据改变了国际上关于全球和中国稻田甲烷排放总量的估算.在对稻田甲