Micro-spectroscopic investigations of highly heterogeneous waste repository materials   总被引：1，自引：0，他引：1  

A.M. Scheidegger  D. Grolimund  C.R. Cheeseman  R.D. Rogers 《Journal of Geochemical Exploration》2006,88(1-3):59

Assuring safe disposal and long-term storage of radioactive and toxic wastes corresponds to a primary environmental task of present societies. To improve any technical limitation, a mechanistic understanding of the processes governing the binding of heavy metals and radionuclides is required. In this study, the significance of synchrotron-based X-ray microprobes for elucidating the spatial distribution and the speciation of radionuclides in highly heterogeneous waste repository materials will be outlined. A case study on the uptake process of Co in cementitious engineered barrier materials exposed to microbial degradation will be presented.  相似文献   

GGR Critical Review of Analytical Developments in 2004–2005     

Janet M. Hergt  L. Paul Bédard  Etienne Deloule  Klaus Peter Jochum  Kathryn L. Linge  Paul J. Sylvester  Matthias Willbold  Jon D. Woodhead 《Geostandards and Geoanalytical Research》2006,30(3):141-142

In 2005 Geostandards and Geoanalytical Research embarked upon a new initiative for its readers. Key researchers in various fields of geoanalytical technique development and their application were identified and invited to provide reviews pertinent to their expertise. As noted in the first of these publications "…instead of revisiting the historical context or decades of development in each analytical technique, the goal here has been to capture a snapshot of "hot topics" across a range of fields as represented in the… literature" (Hergt et al . 2005). Rather than prepare an annual review, a decision was taken earlier this year to provide a biennial summary of progress and accomplishments, in this case for the years 2004–2005. The principal techniques employed in Earth and environmental sciences are covered here, and include laser ablation and multicollector ICP-MS, ICP-AES, thermal ionisation and secondary ion mass spectrometry, as well as neutron activation analysis, X-ray fluorescence and atomic absorption spectrometry. A comprehensive review of the development of reference materials, often essential to these techniques, is also provided. The contributions assembled serve both to keep readers informed of advances they may be unfamiliar with, but also as a means of showcasing examples of the breadth and depth of work being conducted in these fields.  相似文献   

Determination of total selenium in geological samples by HG-AFS？ After enrichment with thiol cotton fiber     

《中国地球化学学报》2006,25(B08):208-209

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Characterization of cristobalite in ash and dome rock from the Soufriere Hills volcano, Montserrat： Implications for respiratory health hazards     

Ben J. Williamson Claire J. Horwell 《中国地球化学学报》2006,25(B08):224-225

A link between the inhalation of respirable silicas （SiO2） and respiratory diseases such as silicosis is widely recognized. Ash from dome collapse eruptions on Montserrat has been found to contain high levels （〉20%） of silicas in the form of cristobalite, tridymite, quartz and/or amorphous silica. The toxicity of these silica polymorphs varies widely. Cristobalite and quartz （tridymite less well established） are viewed as carcinogenic to humans whereas amorphous silica generally shows a reduced biological response. In assessing the potential health effects of volcanic ash particulates it is vital to determine the types and concentration of silicas as well as their size （respirable fraction）, shape and surface properties. The aim of this study is to develop methods to assess potentially toxic respirable airborne silicas in the dome collapse ash （applicable to a range of ash types） and to develop a model to predict the levels and types of respirable silicas from future eruptions. The model is being developed by comparing dome rock with related ash from a series of previous eruption events. Mineralogical assessment using conventional scanning X-ray diffraction （XRD） was hampered by difficulties in differentiating characteristic peaks for cristobalite and tridymite in complex multi-component ash samples （containing high levels of plagioclase）. These difficulties have been largely overcome using an Enraf-Nonius PDS120 diffractometer with curved （120 degrees 20） position sensitive detector （PSD）. The determination of size, shape and elemental characteristics of ash particulate and dome rock samples has been carried out using automated analytical scanning electron microscopy. The quantification of mineral proportions using PSD-XRD was highly successful with an accuracy of 1 to 2 wt%. However, the determination of phase proportions using automated analytical SEM was problematic due to scattering effects and the multiphase nature of many of the particles.  相似文献   

Origin and three-dimensional fluorescence spectrum of the chromophoric dissolved organic matter in Yangtze estuary, East China     

Fan YANG Qinghui HUANG Jianhua LI Xiaomin ZHU 《中国地球化学学报》2006,25(B08):262-262

Dissolved organic matter （DOM） is an important chemical component in natural water. Chromophoric dissolved organic matter （CDOM）, a fraction of optical properties, plays art important role in the biogeochemical cycle of nutrients in aquatic environment. People realized that DOM cycle is crucial in the global carbon and nitrogen flux, and also is inherently related to nutrients and trace metal elements. Therefore, CDOM was concerned by scientists in global oceanography and limnology fields. Water samples were collected from three sections （North Channel, South Channel and Zhuyuan） of the Yangtze （Changjiang River） estuary in March 2006 Three-dimensional excitation emission matrix （3-DEEM） fluorescence spectra were analyzed for those filtrates through Whatman GF/F filters. Dissolved organic carbon （DOC） was also measured by TOC analyzer. The tidal variety was also taken into account. The 3-D EEM fluorescence scans suggested the fluorescence characteristics of humic acid （Ex=332-344 nm, Em=439-451 nm） and fulvic acid （Ex=250-254 nm, Em=472-478 nm） were obvious, and the fluorescence group of protein-like and tyrosine （Ex=230 nm, Em=283 nm） was also found. They are mainly composed of CDOM in the Yangtze estuary. Further data analysis, especially the fluorescence index （f 450/500）, showed that terrestrial signal was rather strong （1.41-1.65） in the surface water, however, some terrestrial CDOM signals of bottom water showed excursions （1.28-1.39）. On the other hand, anthropogenic sign was impressed in the waters of Zhuyuan, which is one of the main drain outlets of Shanghai Metropolis. DOC concentrations ranged from 2.2 mg/L to 3.4 mg/L in Zhuyuan and South Channel, and from 2.0 mg/L to 2.4 mg/L in North Channel. The tide effect played a role in the composition of the CDOM measured by 3-D fluorescence scan technology.  相似文献   

In situ time resolved synchrotron powder diffraction study of thaumasite     

Annalisa Martucci  Giuseppe Cruciani 《Physics and Chemistry of Minerals》2006,33(10):723-731

Structural changes during dehydration and subsequent decomposition in thaumasite Ca₃Si(SO₄)(CO₃)(OH)₆·12 H₂O were studied by in situ synchrotron powder diffraction between 303 and 1,098 K. Evolution of the crystal structure was observed through 28 structure refinements, by full profile Rietveld analysis performed in the P6₃ space group, between 300 and 417 K, whereupon the thaumasite structure was observed to breakdown. Within this temperature range, the cell parameters of thaumasite increased as a function of temperature in a nearly linear fashion up to about 393 K, at which temperature, a slight slope change was observed. Above 400 K, the thermogravimetric analysis revealed that the dehydration process proceeded very rapidly while the refined occupancy of water molecules dropped below a critical level, leading to instability in the thaumasite structure. At a same time, a remarkable change in the unit cell parameters occurring at about 417 K indicated that the crystal structure of thaumasite collapsed on losing the crystallization water and it turned amorphous. This result indicated that the dehydration/decomposition of thaumasite was induced by the departure of the crystallization water. At about 950 K, anhydrite and cristobalite crystallized from the thaumasite glass.  相似文献   

Alteration, evaluation and use of extremaduran granite residues     

C. Albarrán-Liso  M. M. Jordán-Vidal  T. Sanfeliu-Montolio  M. J. Liso-Rubio 《Environmental Geology》2006,49(7):1043-1050

The necessity of eliminating debris from a granite quarry has awakened an interest in applications of by-products, called “marginal arids”, in different fields, like construction and foundations for roadways, restoration, material for the manufacture of artificial rocks, and artesian products etc. Conclusions obtained from the results of tests carried out by X-ray diffraction of granite quarry by-products in Extremadura, Spain, submitted to different treatments, are established. Test pieces from two quarries are analyzed and compared generally and specifically, for commercial use. Finally, conclusions relating to essays in test pieces and mineral dynamics of marginal arid granite are exposed.  相似文献   

The effect of composition and cation ordering on the compressibility of columbites up to 7 GPa     

M. Pistorino  F. Nestola  T. Boffa Ballaran  M. C. Domeneghetti 《Physics and Chemistry of Minerals》2006,33(8-9):593-600

The unit-cell parameters of two columbite samples along the (Fe,Mn)Nb₂O₆ solid solution were measured by means of high-pressure single-crystal X-ray diffraction up to pressures of 7 GPa. The compressional behaviour of these minerals was studied as a function of composition and degree of order. The P–V data of all the samples were fitted with a third-order Birch–Murnaghan equation of state. For the two samples with different compositions but identical degree of order the substitution of Mn for Fe causes a decrease of the bulk modulus K _T0, from 153(1) to 146(1) GPa, without any effect on the pressure first derivative K′. For the two samples with the same composition, cation ordering causes an increase of the bulk modulus from 149(1) to 153(1) GPa and of the pressure first derivative from 4.1(2) to 4.8(3). The compressional behaviour is anisotropic with a linear axial compressibility scheme β _b > β _c ≥ β _a for all samples, regardless of composition and degree of order. Such anisotropy increases sligthly with increasing Mn content.  相似文献   

微量相X射线衍射定量分析的一种简便方法     

何泽能李振山  斯永敏 《岩矿测试》2005,24(2):81-86

阐述了关于微量相X射线衍射定量分析的一种简便方法———近似线性关系法,它适用于二相体系(或基体吸收系数基本恒定的多相体系)材料中微量相的定量分析。该方法不需要在待测样品中加入参考物相,分析时仅需对一条衍射线进行测定,因而分析时间很短,其测定结果与实际含量的相对误差为-10.2%～ 21.4%,与外标法和内标法的测量结果的精度相当。  相似文献   

激光剥蚀等离子体质谱分析中激光剥蚀参数对信号响应的影响   总被引：5，自引：1，他引：5  

徐鸿志靳兰兰  李爱荣帅琴 胡圣虹 《岩矿测试》2005,24(3):171-175

探讨了激光剥蚀等离子体质谱固体微区分析中激光剥蚀参数对元素分析信号灵敏度及稳定性的影响。这些参数包括激光功率、脉冲频率、剥蚀孔经、散焦距离、剥蚀方式等。讨论了优化的激光剥蚀等离子体质谱信号采集及数据处理方式。在全质量范围内选用具有代表性的元素作为研究对象,建立了激光剥蚀的一般性特征规律和266nm紫外激光系统的最佳操作条件。在选定的激光剥蚀参数下,大多数被测元素的检出限为22.8~457ng/g,能够满足固体微区分析的要求。  相似文献