水对Wadsleyite和Ringwoodite电导率的影响及地球动力学意义

在Kawai-1000型多顶砧压机上，利用橄榄石相变人工合成地幔转换带矿物wadsleyite和ringwoodite，其含水量从0．03wt％到2．0wt％变化不等。在压力14～16GPa，温度873K-1273K，通过Mo：MoO2固体反应控制氧逸度的条件下，利用阻抗谱分析方法，测量获得了这些样品的电导率。实验结果显示：wadsleyite的电导率与GH^0.66呈正比，ringwoodite的电导率与GH^0.69呈正比，水极大地增强了样品的电导率；在我们的实验条件下，含水wadsleyite和ringwoodite样品的主要电荷栽体是自由质子。另外，结合大地电磁反演获得的电导率结果和我们的实验数据，我们推断中国东北地区地幔转换带中的水含量约为0．1～0．3wt％，远远高于上地幔中的水含量，这或许表明在410km处可能发生了部分熔融。     

Modelling the OH stretch envelope shape and temperature effects in infrared spectra of hydrous silica and silicate glasses

Simple model calculations show that the reversible temperature effects reported for broad OH-stretching bands in infrared spectra of silica, aluminosilicate, and similar glasses can be explained, in essentials, by homogeneous thermal broadening of the ν(OH) envelope constituents and a decrease in intensity with increasing temperature taking place uniformly across the band. This means that these effects are reasonably consistent with the temperature behaviour of narrow ν(OH) bands of crystalline OH-bearing minerals. These findings leave little room for the previously agreed interpretation in terms of a change in hydrogen-bonding strength, although the dependence of integrated intensity on temperature still remains to be understood. Received: 16 April 1999 / Accepted: 4 April 2000     

厦门大气降水的氢氧同位素研究

本文研究了厦门地区大气降水的氢、氧同位素组成,提出了大气降水线方程的δD＝8．16δ^18O＋10．68,并与全国及全球降水线进行比较,揭示了该降水线方程的特征。对全年氚过剩值（d）及降水线特征研究表明,厦门岛全年降不涞源较为单一,主要为海洋性气团。降水中δD与δ^18O的降水量效应明显,且该影响远远掩盖了温度效应。     

橄榄岩蛇纹石化过程中氢气和烷烃的形成

蛇纹石化过程中形成氢气、烷烃和有机酸,为海底热液区生命活动提供物质和能量来源,可能对地球和其他行星早期生命起源和演化有重要影响。目前关于蛇纹石化过程中氢气和烷烃形成的研究大多以橄榄石为初始物,且温度和压力较低(≤300℃,500bar)。本研究通过一系列的水热实验,研究300~500℃、1~3kbar时橄榄石、斜方辉石、单斜辉石、橄榄岩、玄武岩以及玄武岩与橄榄岩混合物发生蛇纹石化反应后氢气和烷烃的生成。300℃、3kbar时,橄榄石蛇纹石化后产生的氢气远大于辉石蚀变后产生氢气的量。随着温度的增加,400~500℃、3kbar时,橄榄石蚀变程度极低,产生氢气的量低于斜方辉石。单斜辉石实验后没有发生蚀变,不产生氢气和烷烃。400~500℃、3kbar时,橄榄岩蛇纹石化后产生的氢气和烷烃远高于橄榄石、斜方辉石和单斜辉石。玄武岩蛇纹石化后生成氢气和甲烷的量低于橄榄岩,但与玄武岩和橄榄岩混合物相当。这是因为玄武岩的单斜辉石蚀变后形成富铁的透辉石(~8.1%FeO),透辉石的Fe以Fe2+为主,这降低了Fe3+和氢气的量。以上表明,橄榄岩的蛇纹石化不同于橄榄石和斜方辉石。不仅是海底热液蚀变产生氢气和甲烷,洋壳俯冲过程中地幔楔橄榄岩蛇纹石化也会生成氢气和甲烷,但由于洋壳玄武岩的加入,氢气和甲烷的量会远小于橄榄岩蚀变时的量。     

自动调谐器在氢脉泽上的应用结果

本文介绍上海天文台自行研制的氢脉泽调谐［１．２］在我台制造的氢脉泽Ｈ８、Ｈ９、Ｈ１０上的应用．结果表明：氢脉泽自动调谐器有效地改善了氢脉泽的长期稳定度．     

The role of submicrometer aerosols and macromolecules in H2 formation in the titan haze

Previous studies of the photochemistry of small molecules in Titan’s atmosphere found it difficult to have hydrogen atoms removed at a rate sufficient to explain the observed abundance of unsaturated hydrocarbons. One qualitative explanation of the discrepancy nominated catalytic aerosol surface chemistry as an efficient sink of hydrogen atoms, although no quantitative study of this mechanism was attempted. In this paper, we quantify how haze aerosols and macromolecules may efficiently catalyze the formation of hydrogen atoms into H₂. We describe the prompt reaction model for the formation of H₂ on aerosol surfaces and compare this with the catalytic formation of H₂ using negatively charged hydrogenated aromatic macromolecules. We conclude that the PRM is an efficient mechanism for the removal of hydrogen atoms from the atmosphere to form H₂ with a peak formation rate of ∼ 70 cm⁻³ s⁻¹ at 420 km. We also conclude that catalytic H₂ formation via hydrogenated anionic macromolecules is viable but much less productive (a maximum of ∼ 0.1 cm⁻³ s⁻¹ at 210 km) than microphysical aerosols.     

氢钟中使用热敏电阻控温的几个问题

对自1991年以来，在上海天文台氢原子钟上使用的热敏电阻控温系统的几个相关问题进行了讨论与分析。该系统的控温精度可达±5％，粗测温度复制性优于±3‰。     

A radiocarbon chronology for Sanamere Lagoon,Cape York Peninsula,using multiple organic fractions

The selection and pre-treatment of reliable organic fractions for radiocarbon age determination is fundamental to the development of accurate chronologies. Sampling from tropical lakes is particularly challenging given the adverse preservation conditions and diagenesis in these environments. Our research is the first to examine and quantify the differences between radiocarbon ages from different carbon fractions and pretreatment protocols from tropical lake sediments. Six different organic fractions (bulk organics, pollen concentrate, cellulose, stable polycyclic aromatic carbon (SPAC), macrocharcoal >250 μm and microcharcoal >63 μm) were compared at six different depths along a 1.72 m long core extracted from Sanamere Lagoon, Cape York Peninsula, northern Australia. Acid-base-acid (ABA), modified ABA (30% hydrogen peroxide + ABA), 2chlorOx (a novel cellulose pre-treatment method) and hydrogen pyrolysis (hypy) were used to pre-treat the organic fractions. The oldest date is ∼31,300 calibrated years before present (cal yr BP) and the youngest is ∼2800 cal yr BP, spanning ∼28,500 years. The smallest offset between the minimum and the maximum age for different fractions and across pretreatment methods at a given depth was found to be 832 years (between SPAC and pollen) and the largest ∼16,750 years (between pollen concentrate and SPAC). The SPAC fractions pre-treated with hypy yielded older ages compared to all other fractions in most cases, while bulk organics yielded consistently younger ages. The magnitude and consistency of the offsets and the physical and chemical properties of the tested organic fractions suggest that SPAC is the most reliable fraction to date in tropical lake sediments and that hypy successfully removes exogenous carbon contamination.     

Dinosterol δD values in stratified tropical lakes (Cameroon) are affected by eutrophication

In freshwater settings, dinosterol (4α,23,24-trimethyl-5α-cholest-22E-en-3β-ol) is produced primarily by dinoflagellates, which encompass various species including autotrophs, mixotrophs and heterotrophs. Due to its source specificity and occurrence in lake and marine sediments, its presence and hydrogen isotopic composition (δD) should be valuable proxies for paleohydrological reconstruction. However, because the purity required for hydrogen isotope measurements is difficult to achieve using standard wet chemical purification methods, their potential as a paleohydrological proxy is rarely exploited. In this study, we tested δD values of dinosterol in both particulate organic matter (POM) and sediments of stratified tropical freshwater lakes (from Cameroon) as a paleohydrological proxy, the lakes being characterized by variable degrees of eutrophication. In POM and sediment samples, the δD values of dinosterol correlated with lake water δD values, confirming a first order influence of source water δD values. However, we observed that sedimentary dinosterol was D enriched from ca. 19 to 54‰ compared with POM dinosterol. The enrichment correlated with lake water column conditions, mainly the redox potential at the oxic–anoxic interface (E_h OAI). The observations suggest that paleohydrologic reconstruction from δD values of dinosterol in the sediments of stratified tropical lakes ought to be sensitive to the depositional environment, in addition to lake water δD values, with more positive dinosterol δD values potentially reflecting increasing lake eutrophication. Furthermore, in lake sediments, the concentration of partially reduced vs. non-reduced C₃₄ botryococcenes, stanols vs. stenols, and bacterial (diploptene, diplopterol and ββ-bishomohopanol) vs. planktonic/terrestrial lipids (cholesterol, campesterol and dinosterol) correlated with E_h OAI. We suggest using such molecular proxies for lake redox conditions in combination with dinosterol δD values to evaluate the effect of lake trophic status on sedimentary dinosterol δD values, as a basis for accurately reconstructing tropical lake water δD values.     

TSR成因H2S的硫同位素分馏特征与机制

热化学硫酸盐还原反应(TSR)是深层碳酸盐岩油气藏中硫化氢的主要成因机制,目前已在全球发现了50多个TSR成因的大中型含硫化氢天然气田。通过对中国四川盆地含硫化氢气田硫化物的采集与同位素分析,结合全球含硫化氢天然气田硫同位素分析数据,研究了TSR过程中硫同位素的地球化学行为和分馏特征。研究发现,TSR成因的高含硫化氢天然气中,硫化氢与硫酸盐的硫同位素分馏值小于15‰,主要分布范围为2.5‰~13.82‰,平均在10‰。四川盆地海相层系膏岩的硫同位素值分布较宽,并呈现阶梯状变化,而硫化氢的硫同位素则呈现出相似的分布规律,表明各主要含硫化氢气田硫化氢中的硫来自于本层系的硫酸盐,TSR主要发生在各自的储集层中。四川盆地各气田TSR发生的温度条件相似,硫同位素分馏比较接近。TSR过程中硫同位素的分馏过程与硫酸盐本身硫同位素值的高低无关,而与TSR反应程度有关。TSR反应程度越高,硫化氢的硫同位素值与地层硫酸盐的硫同位素越相近。通过系统分析整理全球含硫化氢气田的硫化物硫同位素数据,并结合四川盆地地质条件和油气演化过程,揭示了TSR过程中硫同位素的分馏特征,并绘制出四川盆地和全球各时代硫化氢和石膏的硫同位素分布曲线图,为研究含油气盆地蒸发岩沉积演化和硫化氢成因提供了参考。