Geochemistry of the Rare Earth Elements in Natural Terrestrial Waters：A Review of What Is Currently Knows   总被引：3，自引：0，他引：3  

KEVIN  H  JOHANNESSON ZHOUXIAOPING 《中国地球化学学报》1997,16(1):20-42

The range of observed chemical compositions of natural terrestrial waters varies greatly especially when compared to the essentially constant global composition of the oceans.The concentrations of the REEs in natural terrestrial waters also exhibit more variation than what was reported in seawater,In terrestrial waters ,pH values span the range from acid up to alkaline,In addition,terrestrial waters can range from very dilute waters through to highly concentrated brines.The REE concentrations and their behavior in natural terrestrial waters reflect these compositional ranges,Chemical weathering of rocks represents the source of the REEs to natural terrestrial waters and ,consequently,the REE signature of rocks can impart their REE signature to associated waters,In addition,Because of the typical low solubilities of the REEs both surface and solution complexation can be important in fractionating REEs in aqueous solution.Both of these processes are important in all natural terrestrial waters,however,their relative importance varies as a function of the overall solution composition,In alkaline waters,for example,Solution complexation of the REEs with carbonate ions appears to control their aqueous distributions whereas in acid waters,the REE signature of the labile fraction of the REEs is readily leached from the rocks.In circumneutral pH waters,both processes appear to be important and their relative significance has not yet been determined.  相似文献   

机载扫描激光地面测绘系统分析     

胡以华  魏庆农  章立民 《安徽地质》1997,(1)

本文根据机载扫描激光地面测绘系统的功能和要求，分析了它的工作原理，概括出该系统中扫描激光测距的特点，介绍了一种最新的机载扫描激光地面测绘系统，最后提出了几个需要继续研究的问题  相似文献   

基于常规扫描仪的植物叶面积计算系统   总被引：4，自引：0，他引：4  

李万春  田燕  王鹏云 《气象》2004,30(8):39-41

以计算机和扫描仪的组合技术为基础 ,用ViscalBasic 6 0语言 ,建立了Lea fArea1 0植物叶面积计算系统 ,经过对扫描图片的像素分析 ,实现了植物叶面积测定 ,其测定的误差小于 2‰ ,是一项易于业务化的应用系统。  相似文献   

Analytical methods Of assessing the image quality associated with digital and photographic imaging systems     

Grant H. Thomson 《The Photogrammetric Record》2004,19(107):237-249

The introduction of digital cameras for aerial survey photography and use of scanners with processed aerial film present a number of technical questions concerning the way photography is to be acquired in the future. Among the questions to be addressed are the comparative metric properties of images acquired by each system and the associated image quality characteristics. The new digital camera systems will require very careful appraisal, using well-established methods of assessing metric quality already available to survey organisations. The questions concerning image quality are more difficult to answer, as they require very specialised instrumentation if measurements are to be made directly in practice. Over the course of the past several decades a more analytical approach to assessing image quality has emerged, and one that may be used by individuals. The method is particularly effective where information on the micro-image characteristics of products is made available by the manufacturers concerned. An outline is given of some considerations that need to be taken into account when using an analytical approach, with references given for further reading.  相似文献   

测试超细煤粉粒度的实验研究     

陈杰 《岩矿测试》2004,23(3):183-186

利用激光粒度仪测试超细煤粉的粒度。对测试超细煤粉试样粒度时的试样浓度、测试温度、分散时间、分散剂的种类及浓度等方面的影响进行了实验研究，给出了激光粒度仪测试超细煤粉粒度的最佳实验条件。  相似文献   

鄂尔多斯盆地中生代晚期以来大地热流的变化及其对生态环境格局和演变的影响     

匡耀求  黄宁生  胡振宇  吴志峰  刘宇 《矿物岩石地球化学通报》2004,23(4):318-325

鄂尔多斯盆地的西北部、东北部和南部三个区域现今大地热流平均值分别为56．3、67．3和65．3mW／m^2，对应的生态环境格局也有明显的差异。研究表明，大地热流每增加4～5mW／m^2可使年均地表温度升高约l℃，使最低月均地表温度升高2。C以上。鄂尔多斯盆地东北部的平均大地热流比西北部高出11mW／m^2，东北部年均地表温度可能比西北部高出2～3℃，其最低月均地表温度可能比西北部高出4～6℃。西北部的大地热流平均值已经低于维持地表生态系统延续所需大地热流的临界值(57mW／m^2)，其自然生态系统整体上已经处于脆弱境地；东北部和南部的大地热流均大于57mW／m^2，自然生态系统均尚较稳健。东北部的沙漠化可能是风沙侵入的结果，其生态应该是可以恢复的。整个西北部作为一个整体看，72万年以前大地热流就已衰减到临界值以下，区域生态系统渐趋脆弱，开始整体上向荒漠化演变。  相似文献   

Accurate U-Pb Age and Trace Element Determinations of Zircon by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry   总被引：190，自引：0，他引：190  

Honglin Yuan  Shan Gao  Xiaoming Liu  Huiming Li  Detlef Günther  Fuyuan Wu 《Geostandards and Geoanalytical Research》2004,28(3):353-370

Various zircons of Proterozoic to Oligocene ages (1060-31 Ma) were analysed by laser ablation-inductively coupled plasma-mass spectrometry. Calibration was performed using Harvard reference zircon 91500 or Australian National University reference zircon TEMORA 1 as external calibrant. The results agree with those obtained by SIMS within 2s error. Twenty-four trace and rare earth elements (P, Ti, Cr, Y, Nb, fourteen REE, Hf, Ta, Pb, Th and U) were analysed on four fragments of zircon 91500. NIST SRM 610 was used as the reference material and ²⁹Si was used as internal calibrant. Based on determinations of four fragments, this zircon shows significant intra-and inter-fragment variations in the range from 10% to 85% on a scale of 120 μm, with the variation of REE concentrations up to 38.7%, although the chondrite-normalised REE distributions are very similar. In contrast, the determined age values for zircon 91500 agree with TIMS data and are homogeneous within 8.7 Ma (2 s ). A two-stage ablation strategy was developed for optimising U-Pb age determinations with satisfactory trace element and REE results. The first cycle of ablation was used to collect data for age determination only, which was followed by continuous ablation on the same spot to determine REE and trace element concentrations. Based on this procedure, it was possible to measure zircon ages as low as 30.37 0.39 Ma (MSWD = 1.4; 2 s ). Other examples for older zircons are also given.  相似文献   

Fluid core resonance revealed from a laser extensometer at the Rokko-Takao station, Kobe, Japan     

Atsushi Mukai  Shuzo Takemoto  Takeyasu Yamamoto 《Geophysical Journal International》2004,156(1):22-28

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Laser Ablation ICP-MS Developments and Trends for 2003     

Paul J. Sylvester 《Geostandards and Geoanalytical Research》2005,29(1):41-52

This annual review of laser-ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) covers the year 2003. Significant advances were made in understanding laser-sample interactions. In particular, research defined the distribution of particle sizes produced by the interplay of laser wavelength, laser pulse width and the gas environment of ablation. A link between particle sizes and elemental and isotopic fractionation at both the ablation site and in the ICP was established. Experimental 15 7 nm and femtosecond laser systems were tested with promising results. The number of applications of LA-ICP-MS in geology and environmental Earth science continued to grow with particular interest in element concentration and isotope ratio profiling of materials, linking composition to time scales. In situ isotopic ratio measurements were increasingly made using multicollector magnetic sector ICP-MS instruments. Other applications of wide interest included bulk sampling of rocks and ores prepared as lithium borate glasses; low level analysis of platinum-group elements, rhenium and gold in sulfides, metal and silicates; in situ uranium-lead zircon geochronology; and melt and fluid inclusion analysis.  相似文献   

GGR Critical Review of Analytical Developments in 2003     

Janet M. Hergt  L. Paul Bédard  Etienne Deloule  Kathryn L. Linge  Paul J. Sylvester  Michael Wiedenbeck  Jon D. Woodhead 《Geostandards and Geoanalytical Research》2005,29(1):5-52

The articles that comprise this critical review serve to draw attention to research papers published in specific fields of interest during 2003, provide critical comment on the relevance and importance of individual publications in these fields, and offer an overview of the comparative importance of advances in particular areas. In this way, these articles aim to assist experts in the field by keeping them informed of relevant recent publications, as well as providing an important resource for students or early career researchers who are embarking on studies in an area new to them. This year, five papers provide summaries of developments in bulk sample determinations employing (1) ICP-AES and ICP-MS (trace elements), (2) XRF and atomic absorption spectrometry and INAA, (3) isotope ratio measurements (TIMS, MC-ICP-MS, ICP-MS, ToF), as well as in situ measurements conducted using (4) secondary ion mass spectrometry and (5) laser ablation ICP-MS (trace element and isotope ratio determinations).  相似文献