Isotopic fractionation associated with biosynthesis of fatty acids by a marine bacterium under oxic and anoxic conditions   总被引：1，自引：0，他引：1  

Mark A. Teece  Marilyn L. Fogel  Michael E. Dollhopf  Kenneth H. Nealson   《Organic Geochemistry》1999,30(12):1285

Shewanella putrefaciens (Strain MR-4), a gram negative facultative marine bacterium, was grown to stationary phase under both aerobic and anaerobic conditions using lactate as the sole carbon source. Aerobically-produced cells were slightly enriched in ¹³C (+1.5‰) relative to the lactate carbon source, whereas those from anaerobic growth were depleted in ¹³C (−2.2‰). The distribution of fatty acids produced under aerobic conditions was similar to that resulting from anaerobic growth, being dominated by C_16:1 ω7 and C_16:0 fatty acids with a lesser amount of the C_18:1 ω7 component. Low concentrations of saturated even numbered normal fatty acids in the C₁₄ to C₁₈ range, and iso-C_15:0 were synthesized under both conditions. Fatty acids from anaerobic cultures (average δ¹³C=−37.8‰) were considerably depleted in ¹³C relative to their aerobically-synthesized counterparts (−28.8‰). The distinct differences in isotopic composition of both whole cells and individual fatty acid components result from differences in assimilation pathways. Under aerobic conditions, the primary route of assimilation involves the pyruvate dehydrogenase enzyme complex which produces acetyl-CoA, the precursor to lipid synthesis. In contrast, under anaerobic conditions formate, and not acetate, is the central intermediate in carbon assimilation with the precursors to fatty acid synthesis being produced via the serine pathway. Anaerobically-produced bacterial fatty acids were depleted by up to 12‰ relative to the carbon source. Therefore, detection of isotopically depleted fatty acids in sediments may be falsely attributed to a terrestrial origin, when in fact they are the result of bacterial resynthesis.  相似文献   

210pb as a chronometer and tracer,Burrinjuck Reservoir,Australia     

R. J. Wasson  R. L. Clark  P. M. Nanninga  J. Waters 《地球表面变化过程与地形》1987,12(4):399-414

Cores taken at Burrinjuck Reservoir in southeastern New South Wales have been dated using the first appearance of ¹³⁷Cs, charcoal/bushfire correlations, and annual grass pollen peaks. None of the main ²¹⁰Pb dating models reproduced the ‘known’ chronology. Correlation analysis shows no significant relationship between original ²¹⁰Pb (unsupp.) concentration and grain-size, sedimentation rate or loss on ignition. Differences in sediment source may explain the variations in ²¹⁰Pb. A simple provenance model has been used to interpret the ratio of original ²¹⁰Pb (unsupp.)/²²⁶Ra as a tracer of topsoils and subsoils. High ratios in the reservoir sediments probably indicate eroded topsoils and low ratios eroded subsoils.  相似文献   

吉林省大气降水氢氧同位素浓度场时空展布及其环境效应   总被引：8，自引：0，他引：8  

王凤生 《吉林地质》1997,16(1):51-56

本文详细阐述了吉林省大气降水氢氧稳定同位素（Ｄ，＾１８Ｏ）和放射性同位素氚的浓度场时空展布规律，建立了氢氧同位素的环境效应性模型并论述其水文地质意义，为地下水起源及运移研究提供了新的研究方法与手段。  相似文献   

数字化地震记录分析软件PITSA简介及使用说明   总被引：1，自引：1，他引：1  

JIN Changtai  WANG Songyue  SHENG Mingtao Changchun Institute of Applied Chemistry  Academia Sinica  Changchun 《地震地磁观测与研究》1997,18(4):1-90

“九五”期间我们将建立一批数字化地震台站，紧接着就是数字化记录的常规处理和数字化资料的开发利用问题。这两方面的工作都离不开数字化记录的常规处理软件。由国际地震学和地球内部物理学协会（ＩＡＳＰＥＩ）和联合国科教文组织（ＵＮＥＳＣＯ）以及美国地震学会（ＳＳＡ）联合推荐的由Ｆ．ＳｃｈｅｒｂａｕｍａｎｄＪ．Ｊｏｈｎｓｏｎ完成的一套优秀的数字化分析处理软件ＰＩＴＳＡ（ＰｒｏｇｒａｍｍａｂｌｅＩｎｔｅｒａｃｔｉｖｅＴｏｏｌｂｏｘｆｏｒＳｅｉｓｍｏｌｏｇｉｃａｌＡｎａｌｙｓｉｓ）是一套比较适合我国广大地震工作者使用的软件。ＰＩＴＳＡ的特点是：①在普通微机（ＰＣ机）上安装使用，要求的微机和外部环境都很低，容易安装，占据的硬盘空间小（约２Ｍ）字节；②功能很强，如部分放大，震相拾取、求震级、定震中、分量旋转等常规分析工作它都能很好完成，进一步的分析处理工作如数值微分、积分、基线校正、谱分析、滤波、相关、Ｈｉｌｂｅｒｔ变换，旋转分量、偏振滤波、交义谱、相关谱、画质点运动图、各种模拟地震图的仿真等，它都能方便地实现；③它是菜单操作式软件，易学易用；④我们已有现成的软件，并已被一些地震工作者开发利用。鉴于以上优点，故我们特出版此专辑  相似文献   

海水蒸发时蒸气相硼的浓度及硼同位素分饱研究          下载免费PDF全文

肖应凯  G.H.Swihart  肖云  R.D.Vocke Jr 《盐湖研究》2001,9(4):15-23

本实验目的是研究在空气流的条件下海水－空气界面硼的行为。将２５℃和３５℃的干燥空气流以非冒泡或冒泡的方式通过海水表面或通入海水，采用冰冷凝器和ＫＯＨ溶液浸泡过的纤维素过滤器收集空气流中的硼，当无硼空气流在海水面上通过时，硼会被蒸发而进入空气流中，温度越高，硼含量也较高。空气流通过海水的冒泡试验中，空气流中的硼含量与空气流流量成正比，在此情况下，空气流中的硼主要来自雾化的小液点海水。非冒泡试验中收集的硼同位素分馏表明，较轻的硼同位素１０Ｂ富集在空气流中，表明海水蒸发时，硼同位素分馏主要由动力因素所引起。  相似文献   

云南中西部喜马拉雅期岩浆及成矿研究新进展   总被引：7，自引：2，他引：7  

罗君烈  李志伟 《云南地质》2001,20(3):229-242

云南中西部喜马拉雅期分为4个构造幕，其岩浆侵入活动反映两个热旋回，当岩浆侵入活动结束后才出现火山喷发高潮。笔者首次将新生代内生成矿作用划分为6个时间序列。根据岩石类型组合、侵位时限、成矿专属性，首次将富碱斑岩分为6个超单元、18个单元，从7个方面总结各单元、超单元特征。对富碱斑岩和其它4类岩浆岩进行了演化规律的对比。探讨金顶超大型铅锌矿床与各类岩浆岩的成因关系，详细论述了铅同位素和惰性气体的最新资料并加以对比，初步认为两者深部物源与形成过程有本质上的重要联系，金顶及兰坪盆地内的热水矿床是一套与地幔及幔壳混合有一定关联的独立成矿作用。  相似文献   

硼同位素分馏及其在环境研究中的应用   总被引：3，自引：4，他引：3       下载免费PDF全文

张崇耿  肖应凯 《盐湖研究》2002,10(2):54-60

二十世纪八十年代以来 ,由于硼同位素的测量技术的创新和改进 ,硼同位素地球化学的研究领域不断拓宽。研究表明 ,自然界中δ11B值的变化范围为 -3 7‰～ +5 8‰ ,不同地质体中δ11B值明显不同 ,反之 ,硼同位素组成与生成环境密切相关 ,可以反映其地质成因环境或地质作用过程。近年来 ,硼同位素在研究海水入侵 ,示踪古海洋和古气候条件 ,和判断污染源区等方面取得初步成效。  相似文献   

吉林省二道甸子金矿床同位素地质学及矿床成因探讨   总被引：1，自引：0，他引：1  

张文启  吴尚全 《吉林地质》1996,15(2):31-35

通过对二道甸子金矿床的硫、氢氧及铅同位素地质学研究，认为其成矿物质来源于周围地层，而成矿热液是以岩浆水为主的混合水，矿床成因属于岩浆活化型金矿。  相似文献   

洞穴碳酸钙沉积的古气候记录研究   总被引：22，自引：3，他引：22  

谭明  刘东生 《地球科学进展》1996,11(4):388-395

洞穴碳酸钙是陆地环境中一种极好的古气候信息库。本文比较论述了中外科学家在该领域的研究历史与最新进展，指出该项研究需要通过高精度地质年代学、同位素地球化学和洞穴沉积学密切配合；并结合作者自己的工作，提出洞穴碳酸钙的稳定同位素和年轮记录是我国东部季风区古季风强弱、干湿变化、干旱事件及强降水事件的极好的高分辨档案  相似文献   

Devensian glacial events in Buchan (NE Scotland): A progress report on new OSL dates and their implications     

Alastair M.D. Gemmell  Andrew S. Murray  E.R. Connell 《Quaternary Geochronology》2007,2(1-4):237-242

Optically stimulated luminescence (OSL) dating of a series of glaciofluvial/glaciodeltaic sediments in central Buchan and Aberdeen has recently been undertaken. The aims of this project are to test the chronological model proposed by the most recent regional review and the suggestion that parts of Buchan may have remained ice-free during the last glacial maximum (late marine isotope stage (MIS) 3 and MIS 2 29–15 ka). The preliminary results indicate that during the Devensian (ca. 116–12 ka), extensive areas of Buchan may have been glaciated earlier than previously believed (possibly during MIS 4, 72–60 ka), but parts of the region show no depositional evidence of later glaciation. Some waterlain sediments from the Ugie Valley have yielded OSL ages indicating deposition during MIS 5d to MIS 5a (116–72 ka). We discuss whether the absence of overlying glaciogenic sediments at these locations raises questions about the reliability of the OSL ages or about existing models of the Devensian glaciation of Buchan.  相似文献