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261.
Optimizing sample preparation for the isotopic measurement of 10Be extracted from quartz mineral separates has a direct positive effect on the accuracy and precision of isotopic analysis. Here, we demonstrate the value of tracing Be throughout the extraction process (both after dissolution and after processing), producing pure Be (by optimizing ion exchange chromatography methods and quantifying quartz mineral separate and final Be fraction purity), and minimizing backgrounds (through reducing both laboratory process blanks and 10B isobaric interference). These optimization strategies increase the amount of 10Be available for analysis during accelerator mass spectrometry (AMS), while simultaneously decreasing interference and contamination, and ensuring that sample performance matches standard performance during analysis. After optimization of our laboratory's extraction methodology, 9Be3+ ion beam currents measured during AMS analysis, a metric for sample purity and Be yield through the extraction process, matched the 9Be3+ beam currents of AMS standards analyzed at the same time considering nearly 800 samples. Optimization of laboratory procedures leads to purer samples that perform better, more consistently, and more similarly to standards during AMS analysis, allowing for improved precision and accuracy of measurements used for dating and quantification of Earth surface processes. 相似文献
262.
通过分析、对比发达国家场地污染调查与风险评价技术流程的大量信息,结合工作实践,充分考虑我国的实际情况,视土壤和地下水为相互联系的一个整体,提出了我国现阶段场地尺度土壤和地下水污染调查与风险评价的技术程序和工作内容。 相似文献
263.
海南岛龙湾港滨珊瑚重金属含量的年际变化 总被引:1,自引:0,他引:1
采用等离子体原子发射光谱(ICP AES)技术,测定了1986—1997年海南省琼海市龙湾港(19°20′N、110°39′E)滨珊瑚中的Fe、Cu、Al、Ba、Zn、Mn、Cd、Ni 、Cr重金属含量。结果表明,1993 年珊瑚中 Fe的含量高出其平均值的1.03倍,受到了较明显的Fe污染。另外,珊瑚中的Fe含量在1994、1995年,Cu在1986年,Mn在1993年,Zn在1995年的含量高出各自平均值的0 5~1倍,受到相应重金属的轻微污染。然而,与广东省电白县大放鸡岛滨珊瑚、南沙珊瑚礁沉积物中的重金属含量相比,龙湾港在近12年中海洋珊瑚受重金属的污染不显著。运用多元统计的分析方法,探讨了重金属之间、重金属与降雨量和径流量之间的相关性,并对重金属的污染来源提出一些看法。 相似文献
264.
页岩气储层的特殊性及其评价思路和内容 总被引:6,自引:1,他引:5
为了有效地开展页岩气储层的评价,文中首先总结了页岩气储层相对于常规油气储层的特殊性。指出这些特殊性体现在富含有机质、富含粘土矿物、细小的矿物粒度、极低的孔隙度和渗透率、纳米级孔喉结构、巨大的矿物表面积、复杂的成岩改造、大比例的天然气吸附赋存。在此基础上,从页岩储层性质的特殊性入手,梳理了页岩储层的评价思路和方法。强调了评价过程应遵循评价参数的直接测定与间接计算相结合、分析测试的常规手段与特殊方法相结合、评价对象的孔隙特征与吸附能力相结合。最后,探讨了页岩气储层的评价内容,认为其除了与常规储层相同的储层岩石学特征和物性特征外,还应考虑其吸附天然气的能力及其压裂改造的难易程度,即应包括储层岩石组成特征与空间分布、储层孔渗特征、储集空间特征、储层含气性和储层岩石力学性质等。 相似文献
265.
A. Grassia 《Mathematical Geology》1982,14(4):321-330
Discovery sampling is a simple sampling inspection technique which has been used by internal auditors during the last 30 years. Occasionally it has found application in agricultural research. It will be shown that an amended version of this technique can be used in the sampling of orebodies for the presence of particles of a mineral such as gold, silver, uranite, and so forth. While with the classical Discovery sampling a simple discrete distribution (Multinomial, Poisson, etc.)is involved, in our case convolutions of a discrete (Poisson)and continuous distributions (gamma, lognormal)occur, because of the indirect procedure used in detecting the presence of the mineral in the orebody. Illustrative examples using two distributions of gold particles are given. 相似文献
266.
The occurrence of potentially hazardous trace elements in five Highveld coals, South Africa 总被引:3,自引:3,他引:3
Permian coals of the southern hemisphere are generally considered to contain lower concentrations of sulfides, halogens, and trace elements when compared to northern hemisphere Carboniferous coals. Few studies have considered the trace element content in South African coals, and little or no work has been published for Highveld coals. Of the nineteen coal fields in South Africa, the Highveld coal field is one of the nine currently producing, and is second largest in terms of production. Five run of mine samples and a high ash middlings product from the Number 4 Lower seam were analyzed, totaling six sample sets. Fourteen trace elements (As, Cd, Co, Cr, Cu, Hg, Mn, Mo, Ni, Pb, Sb, Se, V, and Zn) were selected for this study based on the global perception that these elements may be hazardous to human health and/or the environment when they are released during coal utilization. Several sample preparation techniques were tested using certified reference materials (SARMs 18, 19 and 20) to determine the most repeatable technique for these coals. The samples were analyzed by ICP-AES and CVAA (Hg only). Microwave digestion proved to be generally unreliable despite the utilization of several different methods. A slurry direct injection method into the ICP-AES provided good correlations with the reference material, but requires further development to enhance the confidence level in this relatively unexplored technique. Samples prepared based on three ASTM standards for the determination of trace elements in coal provided repeatable results in most instances, and were the preparation methods utilized for the Highveld coals.The trace element values determined for the Highveld coals are generally in good agreement with values available in literature for South African coals, with the exception of Hg, Mn and Cr. Hg values reported here are lower, Cr and Mn higher. Results generally agree well with analyses on the same samples conducted by the United States Geological Survey. When considering the global ranges for trace elements, the Highveld range values are within Swaine's range boundaries with the exception of Cr. Compared to the cited global average values for the fourteen trace elements determined, the values obtained for the Highveld coals generally fall below or well below these average values, with the exception of Cr and Mn. Concentrations of Cd and Cu are lower compared to global average values, and As, Mo, Pb, Se, Sb, and Zn can be considered low to very low. Arsenic is ten times lower compared to typical USA values. Concentrations of Co and Ni are similar to global averages, with V and Hg being very slightly higher. The middlings samples reported higher concentrations of most elements, related to the higher ash content of these samples. Of interest, the chalcophile elements determined are all depleted in the Highveld coals compared to global averages, and the siderophile elements are enriched or comparable to global averages.Risk-based health studies in the USA on coals with similar or higher Hg and significantly higher As contents have not reported negative health effects, and therefore it could be assumed that the mobilization of these trace elements from the five Highveld coals are unlikely to cause human health problems. Work is ongoing to determine the modes of occurrence of these HAPs and to address the partitioning behaviors and speciation states of these elements during coal utilization. 相似文献
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