Associations and mobility of uranium in soils near a depleted uranium （DU） weapons testing site, SW Scotland     

Margaret C. Graham John G. Farmer Ian W. Oliver Angus B. MacKenzie Robert M. Ellam 《中国地球化学学报》2006,25(B08):112-112

Natural uranium has three isotopes, ^238U, ^235U and ^234U, with natural abundances of 99.27 atom %, 0.72% and 0.0055%, respectively. Only ^235U is fissile and the production of nuclear fuel and nuclear weapons involves enrichment of uranium in ^235U. This process also results in separation of ^234U from ^238U, leaving depleted uranium （DU）, with typical ^234U/^238U and ^235U/^238U activity ratios of about 0.19 and 0.013, respectively, as a waste product. The high density, high melting and boiling points and chemical stability of uranium and the availability of DU in relatively pure form mean that DU has many uses, including armour-piercing munitions. Such munitions have been developed in the UK since the 1960s and testing has been carried out by the Ministry of Defence （MoD） at firing ranges such as Dundrennan, SW Scotland and Eskmeals, NW England. The firing of DU munitions can result in the dispersion of DU and its combustion products （oxides） as aerosols or as larger fragments, with the potential for human exposure either directly at the site of detonation or via post-depositional migration in the environment. The aim of this work was to investigate the potential environmental mobility of DU by characterizing the associations of U in soil porewaters with increasing distance from a firing site. To this end, several soil cores located down-wind of the firing site at Dundrennan, near Kirkcudbright, SW Scotland, were collected in May 2006. These were sectioned on-site into 1- or 2-cm depth intervals and porewaters were isolated by centfifugation （10 minutes; 8873 g） on return to the laboratory. Following filtration through 0.2-micron cellulose nitrate filters, the porewaters were analyzed by ICP-QMS （U concentration） and ICP-OES （Fe, Al, Ca, Mg, Mn concentrations）. Sub-samples were also subjected to centrifugal ultrafiltration （100, 30, and 3 kD） and to gel electrophoretic fractionation （agarose; 0.045 M Tris-borate; 20 mA, 30 minutes）. Results showed that U was present at up to 4 μg/L in the soil porewater and that the associations of U varied with sample location and soil depth.  相似文献   

Adsorption of Pentachlorophenol onto Oxide and Clay Minerals： Surface Reaction Model and Environmental Implications     

WU Daqing DIAO Guiyi YUAN Peng PENG Jinlian 《《地质学报》英文版》2006,80(2):192-199

The adsorption of pentachlorophenol （PCP） onto quartz, kaolinite, illite, montmorillonite and iron oxides has been investigated by batch equilibrium techniques. The pH-dependent isotherms are curves with peak values, the position of which is at about pH = 5-6 depending on the mineral species. Based on distribution of both speciation of surface hydroxyls on minerals and PCP in solution a surface reaction model involving surface complexation and surface electrostatic attraction is presented to fit the pH-dependent isotherms, and both reaction constants are calculated. The results show that on quartz and phyllosilicate minerals the predominant adsorption reaction is surface complexation, meanwhile both of surface electrostatic attraction and surface complexation are involved on the iron oxide minerals. The reaction constants of surface electrostatic adsorption are usually one to three orders in magnitude, larger than that of surface complexation. The concentration-dependent isotherms can be well fitted by Langmnir equation with the correlation coefficient R〉0.93 for kaolinite and iron oxides. The maximum adsorption is found in the order： hematite 〉 lepidocrocite 〉 goethite 〉 kaolinite 〉 quartz 〉 montmorillonite ≈ illite, which can be interpreted by consideration of both reaction mechanism and surface hydroxyl density. The significant adsorption of PCP onto mineral surfaces suggests that clay and iron oxide minerals will play an important role as HIOCs are adsorbed in laterite or latertoid soil, which is widespread in South China.  相似文献   

环境矿物材料治理镉（Cd^2＋）污染研究进展   总被引：4，自引：0，他引：4  

商平  王丽娜 《岩石矿物学杂志》2005,24(6):681-685

近年来,环境矿物材料以其经济、有效、无二次污染等特点,在重金属废水处理和土壤修复方面显示出了众多优势,可替代传统的镉污染处理方法。本文综述了国内外环境矿物材料在处理镉污染方面的研究进展,并对今后应用环境矿物材料治理镉污染提出了一些建议。  相似文献   

低聚合羟基铁离子-蒙脱石复合体吸附砷的实验研究   总被引：15，自引：2，他引：15  

姜浩  廖立兵  王素萍 《地球化学》2002,31(6):593-601

将提纯的钙蒙脱石与羟基铁离子溶液作用，制备了低聚合羟基铁－蒙脱石复合体，用化学分析，电子探针分析，粉晶X射线衍射分析，差热分析和穆斯堡尔谱分析等手段。对蒙脱石原样，低聚合羟基铁－蒙脱石复合体和相同条件下制备的铁的含水氧化物进行了表征。在实际土壤的酸度（pH=4-7)和温度（18－40℃）条件下，进行了低聚合羟基铁－蒙脱石复合体吸附有害元素砷的实验，探讨了复合体的砷吸附能力与pH值，温度，吸附时间，砷初始浓度，离子强度间的关系，并与蒙脱石和铁的含水氧化物的砷吸附行为进行了对比，研究表明，在实验条件下，低聚合羟基铁－蒙脱石复合体对砷具有明显的亲合力，低聚合羟基铁－蒙脱石复合体吸附砷的过程有可能是地表岩石和土壤中重要的地球化学过程，是影响砷地地表，特别是土壤中迁移，富集的重要因素。  相似文献   

层柱粘土材料制备与应用研究   总被引：9，自引：1，他引：9  

周春晖  葛忠华  李春生  李小年 《矿物岩石地球化学通报》2002,21(4):242-246

简述了层柱粘土矿物材料研究与应用的现状和进展。利用粘土矿物蒙脱石作母体，通过大体积的铝、锆、硅等交联剂插层可制成层柱多孔材料，在酸催化、氧化还原催化中均有十分广阔的应用前景。研究表明，改进制备工艺后可提高层柱蒙脱石的热稳定性、比表面积和催化活性；通过酸或表面活性剂等预处理，再进行粘土的支撑，可以调节和控制层柱粘土的结构与性能；采用有机改性和模板导向等技术，可获得孔径介于大微孔和中孔之间的新型层柱粘土矿物材料，并应用于大分子催化反应与吸附，为粘土矿物材料合成和应用开辟了新方向。  相似文献   

In situ methods for studying adsorbed phases at the solid/liquid interface: microcalorimetry and ellipsometryLes méthodes d'étude in situ des phases adsorbées : microcalorimétrie et ellipsométrie     

Renaud Denoyel 《Comptes Rendus Geoscience》2002,334(9):689-702

The applications of calorimetric and ellipsometric methods to the understanding of adsorption phenomena occurring at the solid–liquid interface are presented with examples in the field of surfactant adsorption. The various experimental approaches are presented and compared, i.e., immersion calorimetry, titration calorimetry and liquid flow calorimetry. It is shown how they can be used to follow, in situ, the building steps of the surfactant adsorbed layer. On the other hand, ellipsometry allows the adsorption isotherm, the adsorption kinetics as well as the thickness of the adsorbed layer to be determined on well-defined flat surfaces. To cite this article: R. Denoyel, C. R. Geoscience 334 (2002) 689–702.  相似文献   

Synthesis of zeolites using fly ash and their application in removing heavy metals from waters   总被引：1，自引：0，他引：1  

王焰新  郭永龙  杨志华  蔡鹤生  Xavier Querol 《中国科学D辑(英文版)》2003,46(9):967-976

Fly ash is the solid waste of thermal power plants where coal is used as fuel, and its management and utilization have been of environmental concern for decades. Since the technique of synthesizing zeolite from coal fly ash was introduced by Holler[1] (19…  相似文献   

Mechanisms of physico-chemical interaction of mercury with river sediments from a gold mining region in Brazil: Relative mobility of mercury species     

R. Melamed  R.C. Villas Bas  G.O. Gonalves  E.C. Paiva 《Journal of Geochemical Exploration》1997,58(2-3)

Mercury accumulation in the food chain, as a consequence of gold recovery in Brazil, has been an issue of concern. Reactions of Hg in the environment are quite complex, and can involve various Hg chemical species. Laboratory experiments were carried out on Hg⁰ solubility, Hg complexation and sorption on river sediments from a gold mining region in Brazil. The reactivity and the mobility of Hg species were considered. Results indicate that methyl mercury is more mobile than ionic mercury, and that the presence of humic acid enhances drastically the solubility of Hg⁰. The soluble complex formed has a relatively lower interaction at the sediment/water interface and is more prone to spread through the aquatic environment.  相似文献   

Transport in a 2-D saturated porous medium: A new method for particle tracking   总被引：2，自引：0，他引：2  

Frédérick Delay  Hélène Housset-Resche  Gilles Porel  Ghislain de Marsily 《Mathematical Geology》1996,28(1):45-71

A new method for solving the transport equation based on the management of a large numbe of particles in a discretized 2-D domain is presented. The method uses numerical variables to represent the number of particles in a given mesh and is more complex than the 1-D problem. The first part of the paper focuses on the specific management of particles in a 2-D problem. The method also would be valid for three dimensions as long as the medium can be modeled similar to a layered system. As the particles are no longer tracked individually, the algorithm is fast and does not depend on the number of particles present. The numerical tests show that the method is nearly numerical dispersion free and permits accurate calculations even for simulations of low-concentration transport. Because each mesh is considered as a closed system between two successive time steps, it is easy to add adsorption phenomenon without any problem of numerical stability. The model is tested under conditions that are extremely demanding for its operating mode and gives a good fit to analytical solutions. The conditions in which it can be used to best advantage are discussed.  相似文献   

重金属迁移转化模型研究   总被引：14，自引：0，他引：14       下载免费PDF全文

何用  李义天 《水科学进展》2004,15(5):576-583

大量重金属污染物迁移转化的现象和研究成果都表明重金属以泥沙颗粒为载体迁移转化,描述重金属在天然水体中的迁移转化必须紧紧抓住泥沙颗粒运动及重金属与泥沙之间的转化关系进行.为此在对现有的重金属迁移转化数学模型进行概括分类的基础上,根据水沙运动与污染物相互作用关系,分析了泥沙颗粒运动及重金属吸附解吸不平衡过程,并结合水沙数学模型,建立了重金属迁移转化的耦合模型.同时在模型合理性分析的基础上,对模型进行了计算分析,分析表明模型能够合理地反映重金属污染物在水体中的迁移转化过程.  相似文献