Heat capacity of γ-Fe2SiO4 between 5 and 303 K and derived thermodynamic properties     

Wenjun Yong  E. Dachs  A. C. Withers  E. J. Essene 《Physics and Chemistry of Minerals》2007,34(2):121-127

A multi-anvil device was used to synthesize 24 mg of pure γ-Fe₂SiO₄ crystals at 8.5 GPa and 1,273 K. The low-temperature heat capacity (C _p) of γ-Fe₂SiO₄ was measured between 5 and 303 K using the heat capacity option of a physical properties measurement system. The measured heat capacity data show a broad λ-transition at 11.8 K. The difference in the C _p between fayalite and γ-Fe₂SiO₄ is reduced as the temperature increases in the range of 50–300 K. The gap in C _p data between 300 and 350 K of γ-Fe₂SiO₄ is an impediment to calculation of a precise C _p equation above 298 K that can be used for phase equilibrium calculations at high temperatures and high pressures. The C _p and entropy of γ-Fe₂SiO₄ at standard temperature and pressure (S°₂₉₈) are 131.1 ± 0.6 and 140.2 ± 0.4 J mol⁻¹ K⁻¹, respectively. The Gibbs free energy at standard pressure and temperature (ΔG° _f,298) is calculated to be −1,369.3 ± 2.7 J mol⁻¹ based on the new entropy data. The phase boundary for the fayalite–γ-Fe₂SiO₄ transition at 298 K based on current thermodynamic data is located at 2.4 ± 0.6 GPa with a slope of 25.4 bars/K, consistent with extrapolated results of previous experimental studies.  相似文献   

青藏高原崇测冰芯氯离子、硫酸根离子记录     

刘业祥  刘永建  韩建康 《云南地理环境研究》2007,19(3):11-14

通过对青藏高原崇测冰帽一支18．70m冰芯中Cl^-、SO4^2-离子含量变化的分析表明，20世纪90年来Cl^-、SO4^2-离子含量在波动中呈下降趋势，两种离子的周期性波动变化相似，20世纪晚期比早期和中期的波动幅度小，总体上离子含量逐渐减少与温度在波动中上升相一致，但每一次温度的升高与离子含量的下降并非一一对应。陆源物质和青藏高原上的盐湖是冰芯中Cl^-、SO4^2-离子的主要贡献者。揭示了研究地区大气成分和环境变化与气候变化的关系及亚洲粉尘在全球环境变化中的源区地位。  相似文献   

海南三亚地区S₄指数与C/N、ROTI的比较分析          下载免费PDF全文

熊波;  万卫星;  宁百齐;  袁洪;  李国主; 《地球物理学报》2007,50(6)

本文通过利用海南三亚站（1834°N, 10962°E）GPS闪烁/TEC接收机2004年8月到2005年7月间观测数据，在对三亚地区闪烁初步统计分析的基础上，比较分析了观测数据中S₄（幅度闪烁指数）和C/N（载噪比），S₄和ROTI（TEC变化率标准差）的关系，同时对2004年11月7日的闪烁事件进行了具体的分析. 通过比较分析得出：（1）三亚地区全年的闪烁强度具有明显的半年变化，在春秋季出现全年闪烁强度的最大值；（2）S₄与C/N具有很好的负相关性；（3）ROTI可以作为由小尺度不规则结构引起闪烁出现的指示剂.  相似文献   

ERS-2 SAR反演海洋风矢量的研究   总被引：4，自引：0，他引：4       下载免费PDF全文

陈艳玲  黄珹  丁晓利  李志伟 《地球物理学报》2007,50(6):1688-1694

SAR(Synthetic Aperture Radar)反演海洋风矢量是当今微波遥感领域非常有意义的前沿课题. 本文首先介绍了星载SAR估算海面风向、风速的基本原理和三种主流反演算法，接着给出反演的流程图以及重要步骤. 然后，以2002年5月7日香港地区ERS-2 SAR海洋图像为例，对经典的SWDA (SAR Wind Direction Algorithm)－谱分析方法加以改进，求得具有180°模糊度的风向，并用香港天文台气象浮标实测数据消除了风向不确定性. 最后，利用CMOD4 GMF（Geophysical Model Function，地球物理模式函数）计算得到海面上10m高的风速. 与气象浮标站实测资料相比，利用ERS-2 SAR图像获取的海面风向、风速的精度均较高. 这一结果表明：如果对SAR预先进行ADC(Analog to Digital Converter)改正以及精确校准，结合改进的SWDA和CMOD4，可以获得高精度的风矢量.  相似文献   

High-resolution climate variability of southwest China during 57-70 ka reflected in a stalagmite δ18O record from Xinya Cave   总被引：1，自引：0，他引：1  

Li TingYong  Yuan DaoXian  Li HongChun  Yang Yan  Wang JianLi  Wang XinYa  Li JunYun  Qin JiaMing  Zhang MeiLiang  Lin YuShi 《中国科学D辑(英文版)》2007,50(8):1202-1208

A 26-cm-long stalagmite (XY2) from Xinya Cave in northeastern Chongqing of China has been ICP-MS ²³⁰Th/U dated, showing a depositional hiatus at 2.3 cm depth from the top. The growth of the 2.3–26 cm interval determined by four dates was between 57 ka and 70 ka, with a linear growth rate of 0.023 mm/a. We have analyzed 190 samples for δ ¹⁸O and δ ¹³C, mostly in the 2.3–26 cm part. The δ ¹⁸O and δ ¹³C values between 57 ka and 70 ka reveal decadal-to-centennial climatic variability during the glacial interval of Marine Isotope Stage 4 (MIS4), exhibiting much higher resolution than that of the published Hulu and Dongge records during this interval. Speleothem δ ¹⁸O in eastern China, including our study area can be used as a proxy of summer monsoon strength, with lighter values pointing to stronger summer monsoon and higher precipitation, and vice versa. Two decreases in the δ ¹⁸O signature of XY2 record around 59.5 and 64.5 Ka are argued to correspond to the Dansgaard-Oeschger (D-O) events 17 and 18 respectively. The Heinrich event 6 (H6) can be identified in the record as a heavy δ ¹⁸O peak around 60 ka, indicating significant weakening of the monsoon in Chongqing during the cold period. The XY2 δ ¹⁸O record shows very rapid change toward to the interstadial condition of the D-O event, but more gradual change toward to the cold stadial condition. This phenomenon found in the Greenland ice core records is rarely observed so clearly in previously published speleothem records. According to SPECMAP δ ¹⁸O record, the glacial maximum of MIS 4 was around 64.5 ka with the boundary of MIS 3/4 around 60 ka. Unlike the marine record, the speleothem record of XY2, China, exhibits much high frequency variations without an apparent glacial maximum during MIS 4. However, the timing of MIS 3/4 boundary seems to be around 60 ka when the H6 terminated, in agreement with the marine chronology. The growth period of sample XY2 during glacial times probably reflects a local karstic routing of water, rather than having climatic significance. Supported by the National Natural Science Foundation of China (Grant Nos. 40672165, 90511004, 40672202) and the Academician Special Project of Chongqing Science Committee (Grant No. 2003-7835)  相似文献   

铼—锇同位素分析中试样化学预处理方法进展   总被引：4，自引：0，他引：4  

张巽  金立新等 《岩矿测试》2002,21(1):49-54

评述了用于Re-Os同位素体系分析的化学前处理技术的发展。简要介绍了卡洛斯管熔样法、Os的CCl4提取、溴提取和微蒸馏方法。卡洛斯管封闭熔样方法，有效地防止了Os的挥发损失和保证了Os同位素平衡，是一种很有发展前景的熔样方法。蒸馏法仍是分离和纯化Os的有效方法，溶剂（CCl4)提取和溴提取法在许多实验室里应用，而微蒸馏则是Os的二次纯化的主要方法。Re的化学分离和纯化仍是离子交换和萃取法。引用主要文献29篇。  相似文献   

塔里木盆地哈得4油田成藏年代学研究   总被引：26，自引：0，他引：26  

赵靖舟  田军 《岩石矿物学杂志》2002,21(1):62-68

哈得4油田是近年来在满加尔凹陷北部发现的第一个海相油田，一直被认为是喜山期形成的油藏。然而，根据包裹体测温、伊利石K／Ar同位素测年以及油气水界面追溯等多种方法对其成藏年代重新研究表明，该油田主力油藏石碳系CⅢ油藏主杰晚海西期形成的古油藏，C5薄砂层油藏则可能为喜山期由CⅢ油藏垂向调整形成的次生油藏。  相似文献   

中国南京与美国德克萨斯稻田甲烷排放的比较   总被引：8，自引：0，他引：8  

Huang Yao  Jiang Jingyan  Zong Lianggang  Ronald L. Sass  Frank M. Fisher 《大气科学进展》2001,18(6):1121-1130

Field measurements of methane emission from rice paddies were made in Nanjing, China and in Texas, USA, respectively. Soil temperature at approximately 10 cm depth of the flooded soils was automatically recorded. Aboveground biomass of rice crop was measured approximately every 10 days in Nanjing and every other week in Texas. Seasonal variation of soil temperature in Nanjing was quite wide with a magnitude of 15.3℃ and that in Texas was narrow with a magnitude of 2.9℃. Analysis of methane emission fluxes against soil temperature and rice biomass production demonstrated that the seasonal course of methane emission in Nanjing was mostly attributed to soil temperature changes, while that in Texas was mainly related to rice biomass production. We concluded that under the permanent flooding condition, the seasonal trend of methane emission would be determined by the soil temperature where there was a wide variation of soil temperature, and the seasonal trend would be mainly determined by rice biomass production if there are no additional organic matter inputs and the variation of soil temperature over the rice growing season is small.  相似文献   

面向国土资源调查的地理信息系统集成方案研究     

邬伦  韦中亚  刘宇  张远惠 《地理与地理信息科学》2001,17(2):5-10

分析国内外国土资源调查中GIS方法研究和应用的现状和趋势 ,提出基于多层次GIS集成的国土资源大调查思路 ,介绍和总结在大调查中应该关注的地理信息系统方法和应用。同时指出我国国土资源大调查的重点在开展微型化嵌入式GIS、三维 /四维GIS、网络GIS等方面的研究。  相似文献   

SO4^2—、NO3^—对氯同位素测定的干扰及其消除   总被引：1，自引：2，他引：1       下载免费PDF全文

逯海  肖应凯 《盐湖研究》2001,9(2):7-12

在石墨存在下用正热电离质谱法测定 Cs2 Cl+正离子是氯同位素测定的最佳方法 ,但实验过程中发现 ,SO42 - 和 NO3- 的存在对测定的干扰较严重。在系统地研究了 SO42 - 和 NO3- 对氯同位素测定影响的基础上 ,定性地给出了在 SO42 -和 NO3-影响下 ,部分仪器聚焦参数的变化 ,并对影响的机理做了一些解释。着重探讨了不产生影响的 SO42 - 和 NO3- 的最高浓度及 SO42 - 和 NO3- 的消除方法 ,以期指导相关的工作  相似文献