Covariance of dark energy parameters and sound speed constraints from large H i surveys

An interesting probe of the nature of dark energy is the measure of its sound speed, c _s. We review the significance for constraining sound speed models of dark energy using large neutral hydrogen (H  i ) surveys with the square kilometre array (SKA). Our analysis considers the effect on the sound speed measurement that arises from the covariance of c _s with the dark energy density, Ω_de, and a time-varying equation of state,   w ( a ) = w ₀+ (1 − a ) w _a   . We find that the approximate degeneracy between dark energy parameters that arises in power spectrum observations is lifted through redshift tomography of the H  i -galaxy angular power spectrum, resulting in sound speed constraints that are not severely degraded. The cross-correlation of the galaxy and the integrated Sachs Wolfe (ISW) effect spectra contributes approximately 10 per cent of the information that is needed to distinguish variations in the dark energy parameters, and most of the discriminating signal comes from the galaxy auto-correlation spectrum. We also find that the sound speed constraints are weakly sensitive to the H  i bias model. These constraints do not improve substantially for a significantly deeper H  i survey since most of the clustering sensitivity to sound speed variations arises from   z ≲ 1.5  . A detection of models with sound speeds close to zero,   c _s≲ 0.01,  is possible for dark energy models with   w ≳−0.9  .     

湖相介形类壳体微量元素在古环境重建中的应用

湖相介形类壳体微量元素（本文主要指Mg和Sr）是重建古环境的重要指标之一,可以定性或定量地反映湖水信息。自20世纪80年开始应用以来,经过30余年的发展取得了很大进展。在古环境重建过程中主要存在两类影响因素：（1）其宿生水体中M/Ca比值（M主要指Mg和Sr）的影响因素：季节变化、微环境差异和湖泊演化过程,这类因素通过对宿生水体中M/Ca比值来影响介形虫壳体中的M/Ca比值,进而造成古环境重建结果的误差增大或可靠性降低;（2）介形类壳体微量元素分配系数的影响因素：宿生水体中M/Ca比值、温度、碱度等,这类因素能够直接影响介形类壳体分泌、钙化的生命-化学过程的因素,是定量重建的重要影响因素。加强现代介形类生活习性和微量元素组成变化过程的研究可以消除或减小以上影响因素对古环境重建的影响,提高介形类壳体化石中微量元素组成在古环境重建研究中的精度和可靠性。     

东北地区五大连池湖相沉积物正构烷烃和单体碳同位素特征及其古植被意义

对中国东北地区小兴安岭与松嫩平原过渡带五大连池青石钻孔湖相沉积物进行了有机地球化学分析,检测出丰富的正构烷烃生物标志化合物.本文主要讨论了正构烷烃的分布及其单体碳同位素组成特征.正构烷烃具有前峰型和双峰型两种分布特征,表明其有机质为混合来源,包括低等菌藻类生物和陆生高等植物输入.正构烷烃的分布特征表明,自35.2ka B.P.以来,nC27/nC31和ACL指标共同记录了东北地区小兴安岭与松嫩平原过渡带的植被以草本为主.对C27、C29和C31长链正构烷烃进行了单体碳同位素测定,并利用二元模式估算了C3和C4植物相对生物量,结果表明,自35.2ka B.P.以来,研究区的植被以C3植物为主.期间在典型冷暖气候事件中,受温度变化的影响,C3/C4植物的相对生物量有明显的变化,在全新世大暖期(6.0ka B.P.),受温度升高影响,C3植物的生物量显著减少,C4植物的生物量则明显增加;而在两次典型冷气候事件(中全新世降温事件8.2ka B.P.和新仙女木事件12.9ka B.P.)时期,受温度降低影响,C3植物的生物量有增加的趋势,C4植物的生物量则相对呈减少的趋势;在末次冰盛期21.0ka B.P.时,受明显低温特征的影响,C3植物生物量高达80.0％,这可能是当时低温的气候特征抑制了C4植物的生长.研究结果对探索我国东北地区C3/C4植物分布格局,并为评估未来气候演化对该地区植被格局和农业生产的影响提供科学依据.     

Reference Materials in Geoanalytical Research -Review for 2004 and 2005

This review gives an overview of the use and development of reference materials of geochemical and environmental interest in the literature of the years 2004 and 2005. In these years the performance of existing methods has been improved and new geochemical applications using new techniques have been developed. Accordingly, there was an increasing need for new reference materials, especially for in situ microanalysis and for precise stable isotope measurements. In addition, there was a notable trend for further characterisation of existing reference materials, mainly for the platinum-group elements. This review focuses on five topics: reference materials for platinum-group elements, reference glasses for in situ microanalysis, zircon reference materials, isotopic reference materials, and the development and certification of reference materials.     

2004–2005 Analytical Developments in Secondary Ion Mass Spectrometry

This review of the literature from 2004 and 2005 concerning secondary ion mass spectrometry (SIMS) highlights the contribution the technique has made in the fields of petrology, geochronology, cosmochemistry and material sciences. In petrology, much research was devoted to the measurement of stable isotopes and trace elements by developments in multicollection acquisition, with emphasis on low atomic mass number elements. Elements studied in particular were S (in sulfides), O (in garnets), C (in sedimentary organic matter), Cl (in glasses) and Si. Novel applications of SIMS to geochronology have included the measurement of young zircon grains by the U-Pb and U-Th decay methods. An increasing number of studies have combined U-Pb geochronology with the measurement of trace elements or stable isotopes in zircon.     

黔西北地区土壤重金属地球化学背景及管理目标值

基于贵州省毕节地区1∶25万土地质量地球化学调查的1 308件深层土壤样品重金属含量数据,研究了土壤重金属含量分布及其地球化学背景特征,与全国土壤比较,黔西北土壤重金属地球化学背景值显著高于全国土壤元素背景值,但是,与我国西南地区土壤元素背景值接近。黔西北地区土壤重金属含量与地质背景关系密切,不同地质单元区土壤重金属含量存在显著差异,石炭系地层发育的土壤呈Pb、Zn地球化学高背景,二叠系中统风化形成的土壤呈Cd、Hg地球化学高背景,黔西北地区不仅存在土法炼锌造成的土壤重金属污染,土壤重金属地球化学高背景也是影响土壤重金属富集的重要因素。统计表明,黔西北地区二叠系中统风化土壤Cd管理目标值高于我国农用地土壤Cd风险管制值(2.0×10^-6),认为在确定黔西北地区土壤重金属管理目标时,应充分考虑不同地质单元区土壤重金属地球化学背景值差异及其生态环境效应的影响。     

无锡马山抽水蓄能电站地面厂房边坡稳定性分析

以无锡马山抽水蓄能电站地面厂房建筑过程中形成的人工边坡为例,在对其工程地质剖面分析并找出可能的滑动模式后,利用极限平衡法和有限元法分析了4个典型地质剖面的稳定性安全系数以及应力应变关系。结果表明,通过对该边坡的极限平衡法得到了2-2剖面的安全系数和通过有限元法得到的计算结果比较接近,且都满足相关规范的要求;坡体的最大位移发生在高程为－20 m和－5.0 m附近,其值为－22 mm;最大主应力位于高程－45.0 m处,值为0.134 MPa;最小主应力位于坡内深处,其值为－6.22 MPa。同时,提出了下一阶段应考虑时间效应,对边坡的变形进行分析。     

不同氧化还原条件下铅锌矿尾砂中重金属元素活化迁移规律

以广西大厂镇鲁塘铅锌矿尾砂为研究对象,通过淋滤实验研究了不同氧化还原条件下尾砂中Cu、Cd、Zn、Pb和As等元素的活化和迁移规律。结果表明：经高浓度氧化、高浓度还原条件处理的尾矿表现为pH<7的酸性环境,经低浓度氧化环境条件处理的尾砂呈现pH>7的弱酸性至弱碱性环境;尾砂中Cu、Cd元素活化迁移受pH值的影响明显,即高浓度还原和高浓度氧化条件可以促进Cu和Cd元素的迁移,酸性条件对Cu和Cd元素的迁移起到促进作用;Zn与Cd元素存在竞争吸附关系,但二者仍有明显差别;Pb和As元素受到还原条件的影响,能有效促进Pb和As元素的释放迁移。在淋滤实验前期,铅锌矿的表面阻力较小,由于环境酸碱性的改变,初始尾砂对重金属元素的吸附位能发生变化,重金属元素初期迁移能力得到加强;淋滤后期,矿物颗粒表面由于发生氧化还原反应,促使颗粒表面的阻力增加,重金属元素的溶出量减少,迁移能力受到抑制。     

黑龙江省达连河油页岩地球化学特征及成因探讨

论述了达连河含煤段油页岩及油页岩段油页岩的地球化学特征,探讨了两套油页岩成因。这两套油页岩地球化学性质有很多相似之处,主要表现为油页岩都属于中熔或难熔的硅质灰分,SiO₂、Al₂O₃及Fe₂O₃含量很高;无机元素 Mn/Ti小于0.1,Sr/Ba为0.1～0.5,V/Ni为2.6～7.0;有机质类型以腐泥腐殖型为主,正构烷烃OEP值为1.55～3.67,具奇碳数优势,主峰碳为nC₂₃和C₂₉,Pr/Ph比值平均高达2.30,具强烈的姥鲛烷优势,Pr/nC₁₇比值为1.18～3.20,说明这两套油页岩都形成于淡水、近岸及弱氧化-弱还原的湖沼相沉积环境。但含煤段油页岩沉积时期高温、湿润的古气候条件下的喜湿植物面貌,使油页岩母质类型具有较多的富氢组分,这是造成两套油页岩品质差异的主要原因。