Re-Os Isotopic Measurements at the Femtomole Level in Natural Samples

Here we describe a new chemical separation method for Os and an improved mass spectrometric procedure for Re and Os. This technique is based on the selective extraction of OsO₄ from aqueous solution in liquid bromine. Among other advantages, this procedure avoids the cumbersome distillation procedure for Os and uses only commercial "off the shelf" PFA teflon labware. Blank levels for 0.5 g sample sizes are: 0.06 pg and 0.5 pg for Os and Re respectively. Samples containing as little as 1 pg g⁻¹ Os can be analysed reliably with this method. Adaptation to other dissolution methods is also discussed.     

Assessing aboveground net primary production of vascular plants in marshes

Information of aboveground net primary production (ANPP) in marshes has been limited by the lack of accurate methods for assessment. Most popular methods have weaknesses that cause either underestimates or overestimates of ANPP values. The nondestructive growth kinetics monitoring method used by Williams and Murdoch (W-M) has provided, perhaps, a most ideal and reasonable assessment of ANPP inJuncus roemerianus marshes Unfortunately, the W-M procedure is difficult to carry out and it is restricted toJuncus marshes. I present here a modification of the W-M procedure. The modified procedure applies the principle of the original W-M method while eliminating the need to monitor growth kinetics of individual plants. The modified ANPP procedure requires monthly harvests of the above-ground plant biomass over a period of 1 yr and the estimation of mean residence time of the plant. The modified W-M procedure was comparable to the original procedure inJ. roemerianus marshes of northern Florida. This modified procedure has the potential to be applied to marshes other than those dominated byJuncus.     

利用Radon变换进行三度体重磁异常反演

从Ｒａｄｏｎ变换角度分析解释了重磁三度体异常和二度体异常之间的等价关系，提出了利用Ｒａｄｏｎ正变换将三度体异常转化为二度体异常，对二度体异常做一维反演，然后将反演结果通过反Ｒａｄｏｎ变换实现三维场源图象重建的思想，并付诸实施，在微机上通过模型检验，证明该方法实用、可行。     

A Robust Procedure for High‐Precision Determination of Rare Earth Element Concentrations in Seawater

This study reports a robust procedure that permits precise measurement of all fourteen naturally occurring rare earth element (REE) concentrations, present at ng kg^?1 to sub ng kg^?1 levels, in ~ 100 ml seawater. This procedure is simple and can be routinely applied to measure seawater REEs with relatively high sample throughput. The procedure involves addition of a ¹⁴²Ce‐¹⁴⁵Nd‐¹⁷¹Yb‐enriched spike mixture, iron co‐precipitation, REE purification with chromatographic separation and the use of a magnetic‐sector‐field ICP‐MS (Element 2) coupled with a desolvating sample introduction system (Aridus 1). Critical steps of the procedure, including co‐precipitation pH and matrix removal, have been optimised through a set of experiments described here. The accuracy of the new procedure was assessed against a gravimetric mixture of REEs, and the precision was demonstrated by repeated measurement of two well‐mixed natural seawaters. Repeated analyses of these seawater reference materials (RMs), using ~ 100 ml seawater for each aliquot, indicate precision of 3% (1s) for the REEs. Measured REE concentrations of two uncertified seawater RMs (CASS‐4 and NASS‐5) are consistent with published values, and REE concentrations of the GEOTRACES intercalibration samples show good agreement with those reported by other participant laboratories. REE concentrations for other intercalibration samples (SAFe and Arctic PS70) are also reported.     

Finite element analysis of consolidation of layered clay soils using an elastic visco-plastic model

This paper presents a general one-dimensional (1-D) finite element (FE) procedure for a highly non-linear 1-D elastic visco-plastic (1-D EVP) model proposed by Yin and Graham for consolidation analysis of layered clay soils. In formulating the 1-D FE procedure, a trapezoidal formula is used to avoid the unsymmetry of the stiffness matrix for a Newton (modified Newton) iteration scheme. Unlike many other 1-D FE approaches in which the initial in situ stresses (or stress/strain states) are considered indirectly or even not considered, the initial in situ stress/strain states are taken into account directly in this paper. The proposed FE procedure is used for analysis of 1-D consolidation of a clay with published test results in the literature. The FE modelling results are in good agreement with the measured results. The FE model and procedure is then used to analyse the consolidation of a multi-layered clay soils with a parametric study on the effects of the variations of creep parameters in Yin and Graham's 1-D EVP model. It is found that the creep parameters ψ/V and t₀ have significant influence on the compression and porewater pressure dissipation. For some boundary conditions, changes of parameters in one layer will have some effects on the consolidation behaviour of another layer due to the different consolidation rates. Finally, the importance of initial stress/strain states is illustrated and discussed. Copyright © 1999 John Wiley & Sons, Ltd.     

Reliable Determination of Ge in Solid Environmental Samples Using a Chemical Preparation Procedure Developed for Si Isotopes and ICP‐MS Analysis

Germanium (Ge) exists at trace levels in the Earth's crust and is a powerful geochemical tracer of the silicon (Si) cycle. This study proposes a simple and reliable method for determining Ge contents in environmental samples using ICP‐MS. As Si and Ge have very similar chemical properties, we investigated the applicability of the chemical preparation procedure developed for Si isotopes for the determination of Ge in environmental samples. Advantages of this procedure are as follows: (a) efficient removal of the matrix and main interferences affecting Ge determinations by ICP‐MS, (b) a low limit of detection (6 ng l^?1), (c) relative repeatability of approximately 3% obtained on ⁷⁴Ge and (d) robustness and accuracy based on agreement within errors with the published Ge values for rock reference materials (BHVO‐2, AGV‐2 and BCR‐2). This procedure allowed revision of the Ge values of three soil reference materials (1.67 ± 0.09 μg g^?1, 2.41 ± 0.18 μg g^?1, 1.89 ± 0.10 μg g^?1 for GBW 07401, GBW 07404 and GBW 07407, respectively) and proposal of a value for the plant reference material ERM‐CD281 (70 ± 3 μg g^?1). This method provides a convenient procedure for determining Ge mass fractions in environmental samples and opens the possibility of coupling two tracers of the Si biogeochemical cycle with a single measurement procedure.     

Two Reference Samples for Assessing Analytical Data Reliability in Geochemical Investigations

The planned procedure for developing two reference samples, coal ash from the Kansk-Achinsk basin, ZUK-1, and silt from Lake Baikal, BIL-1, is described.     

High Precision Hf-W Isotopic Measurements in Meteoritic Material Using Negative Thermal Ionisation Mass Spectrometry (NTIMS)

This paper presents a two-stage anion-exchange procedure for tungsten extraction, an improved mass spectrometric procedure for tungsten analysis and a simplified chemical separation and TIMS procedure for the determination of Hf concentrations. The chemical separation of tungsten is based on its complexing properties with HF and H₂O₂. The blank level for a sample size of 300 mg is about 80 pg for tungsten. The procedure is designed for the high sensitivity of negative thermal ionisation mass spectrometry (NTIMS) provided by the use of Mg oxide as an emitter on Ir filaments. Tungsten can be readily measured with a high precision in various meteoritical material and especially in small W-poor silicate fractions. Samples containing as little as a few ng g^-1 tungsten can be analysed reliably with this method.     

Additional Certified Values for CCRMP Soils SO-1 to -4

New mean values for up to 11 major and minor and up to 11 trace elements in soils SO-1 to SO4 have been calculated by two procedures. Analytical results received by CCRMP subsequent to the certification program of 1979 were included. In one instance, the same procedure as used for certification wherein all results except those rejected on chemical and/or statistical considerations was followed, but little improvement over the 1979 calculations was obtained. The other procedure is proposed by the authors for use in identifying concentration range intervals wherein maximum interlaboratory consensus is observed. The application of this procedure has permitted the certification of the four soils for the content of 24 elements not previously certified.     

天然硅酸岩铷锶同位素稀释测定小交换柱化学制备方法研究

本篇报道用于铷锶同位素年代测量的小柱分析流程。方法是在我们1972年草酸淋洗流程的基础上建立的。同时参考W.康普斯敦教授1977年介绍的小交换柱铷锶化学流程。样品提取方式、交换柱分离条件和操作步骤,是根据自己的实验确定的。流程有自身的特点。     

A Characterization of Symmetric Isofactorial Models

The paper examines symmetric isofactorial models. A necessary and sufficient condition for a bivariate stationary random function to be isofactorial is given. Using this characterization, a procedure for checking whether an isofactorial model is appropriate is outlined. If data indicates that an isofactorial model is adequate, the procedure also provides a method for identifying the factors of the model. The paper concentrates on the case where Z(x) takes values 0, 1, 2,..., N and the general case is discussed briefly.     

磷灰石中氦扩散参数的确定方法及求解过程

基于Arrhenius 关系图解, 详细介绍了磷灰石中氦扩散参数及其封闭温度的确定方法及求解过程,并以Wolf et al（1996） 的阶段升温数据为例进行了演示性和验证性计算。主要求解步骤如下：（1）对磷灰石做阶段升温试验,得到每一阶段的氦 累积丢失分数;（2）根据球形颗粒的扩散模型公式计算出每一阶段的lnD/a²;（3）以lnD/a²作为纵坐标,1/ T作为横坐标作 图（T 为阶段升温试验每一阶段的温度）,如果在某一温度范围内得到的是一条直线,说明在这一温度范围内磷灰石中氦的 扩散遵从Arrhenius关系式,那么在Arrhenius关系图解上,扩散参数E 和ln D0/a²可通过直线的斜率和截距得到;（4）把E 和 lnD0/ a²代入封闭温度的计算公式,通过迭代计算就可得到磷灰石的封闭温度。求解过程中需要注意两个关键问题：（1）由 于1/ T 为小数,对于磷灰石的氦扩散数据来说,需乘以10⁴ 将其化为整数,与纵坐标的数值为同一数量级;（2）计算封闭温 度时,需把冷却速率的单位从“℃/Ma”转化为“ K/s”,转化时需注意1 ℃ /Ma = 1 K/Ma。     

Determination of Rare Earth Elements, Sc, Y, Zr, Ba, Hf and Th in Geological Samples by ICP-MS after Tm Addition and Alkaline Fusion

We present a revised method for the determination of concentrations of rare earth (REE) and other trace elements (Y, Sc, Zr, Ba, Hf, Th) in geological samples. Our analytical procedure involves sample digestion using alkaline fusion (NaOH-Na₂O₂) after addition of a Tm spike, co-precipitation on iron hydroxides, and measurement by sector field-inductively coupled plasma-mass spectrometry (SF-ICP-MS). The procedure was tested successfully for various rock types (i.e., basalt, ultramafic rock, sediment, soil, granite), including rocks with low trace element abundances (sub ng g⁻¹). Results obtained for a series of nine geological reference materials (BIR-1, BCR-2, UB-N, JP-1, AC-E, MA-N, MAG-1, GSMS-2, GSS-4) are in reasonable agreement with published working values.     

The determination of chlorine in rocks and minerals by pyrohydrolytic method

In this paper a porcedute of pyrohydrolysis spectrophotometric determination has been established for chlorine in rocks and minerals. The selection of accelerator and its required quantity, the time and temperature of sample decomposition and the influence of interferring elements and other factors are also discussed in detail. Because samples are usually fused with alkalis, higher blank is an insurmountable problem. However, with our procedure, the above-mentioned drawback can be effectively overcome, and the determination of trace chlorine either in large or in minor quantities of samples also is rather ideal. The determined results indicate that the relative standard deviations are 8.7% in the former and 4.5% in the latter case. This procedure is simple, rapid and well reproduceable. The detection limit of the method is 10 ppm. The results obtained by our procedure are in good agreement with the proposed values from two reference samples in China (DZΣ-1 and DZΣ-2) and one international geochemical reference sample (RGM-1). This method has proved itself to be reliable.     

Deriving landslide dam geometry from remote sensing images for the rapid assessment of critical parameters related to dam-breach hazards

Dam-breaches that cause outburst floods may induce downstream hazards. Because landslide dams can breach soon after they are formed, it is critical to assess the stability quickly to enable prompt action. However, dam geometry, an essential component of hazard evaluation, is not available in most cases. Our research proposes a procedure that utilizes post-landslide orthorectified remote sensing images and the pre-landslide Digital Terrain Model in the Geographic Information System to estimate the geometry of a particular dam. The procedure includes the following three modules: (1) the selection of the reference points on the dam and lake boundaries, (2) the interpolation of the dam-crest elevation, and (3) the estimation of dam-geometry parameters (i.e., the height, length, and width), the catchment area, the volumes of barrier lake and landslides dam. This procedure is demonstrated through a case study of the Namasha Landslide Dam in Taiwan. It was shown the dam-surface elevation estimated from the proposed procedure can approximate the elevation derived from profile leveling after the formation of the landslide dam. Thus, it is feasible to assess the critical parameters required for the landslide dam hazard assessment rapidly once the ortho-photo data are available. The proposed procedure is useful for quick and efficient decision making regarding hazard mitigation.     

贵州省1∶50万数字地质图的编制及其使用

本文以贵州省 1∶50万数字化地质图为例 ,阐述了地质图数字化的必要性及工作流程 ,讨论了地质图数字化的工作方法以及工作之中存在的问题 ,并介绍 1∶50万数字化地质图在地质工作中的用途和使用方法。     

Trace Metal Speciation of USGS Reference Sample MAG-I

The USGS reference sample marine mud MAG-1 has been subjected to a sequential extraction procedure designed to partition the constituent trace metals into five fractions: I-exchangeable; II- bound to carbonates; III-bound to Fe-Mn oxides; IV- bound to organic matter; V- residual. The analytical approach involved successive chemical extractions and the subsequent determination of trace metal concentrations (Co, Cu, Ni, Pb, Zn; Fe, Mn) in the leachates by atomic absorption spectrophotometry. The chemical speciation results obtained on four replicate sub-samples demonstrate that the coefficients of variation for metal concentrations in the individual fractions are generally better than + 10%. Comparison with published values for total trace metal concentrations in the MAG-1 sample suggests that the overall accuracy of the chemical extraction procedure is satisfactory.     

Determination of Trace Element Mass Fractions in Ultramafic Rocks by HR‐ICP‐MS: A Combined Approach Using a Direct Digestion/Dilution Method and Preconcentration by Coprecipitation

A procedure is described for the determination of thirty‐seven minor and trace elements (LILE, REE, HFSE, U, Th, Pb, transition elements and Ga) in ultramafic rocks. After Tm addition and acid sample digestion, compositions were determined both following a direct digestion/dilution method (without element separation) and after a preconcentration procedure using a double coprecipitation process. Four ultramafic reference materials were investigated to test and validate our procedure (UB‐N, MGL‐GAS [GeoPT12], JP‐1 and DTS‐2B). Results obtained following the preconcentration procedure are in good agreement with previously published work on REE, HFSE, U, Th, Pb and some of the transition elements (Sc, Ti, V). This procedure has two major advantages: (a) it avoids any matrix effect resulting from the high Mg content of peridotite, and (b) it allows the preconcentration of a larger trace element set than with previous methods. Other elements (LILE, other transition elements Cr, Mn, Co, Ni, Cu, Zn, as well as Ga) were not fully coprecipitated with the preconcentration method and could only be accurately determined through the direct digestion/dilution method.