长江中下游地区地下水中铁锰元素的形成及其分布规律

通过实际资料，论证了地下水中Ｆｅ、Ｍｎ元素的形成、含量及其分布规律，除了与地下水的含水介质成分、上覆岩土性质、地下水的迳流条件、地下水的Ｃｌ离子及酸碱度有关外，主要受氧化还原环境的控制。     

近百年来长江中游牛轭湖沉积物铅元素富集记录及其环境意义——以长江荆江段牛轭湖群为例

通过对长江荆江段天鹅洲、中洲子和尺八3个牛轭湖钻孔沉积物进行短寿命放射性核素、粒度、磁学、铅元素测试与史志资料分析,在利用²¹⁰Pb比活度计算平均沉积速率,并结合史志资料与沉积物特征指示的事件进行沉积物年代校核基础上,运用地表物质非自然富集系数(EF值)方法,分析了牛轭湖沉积物铅元素富集状况。结果表明:三钻孔铅元素非自然因素富集特征基本一致,均起始于20世纪80年代初,并于2000年后呈下降状态,与我国铅污染历史及禁用含铅汽油的时间基本吻合;利用沉积物中铅元素非自然因素富集事件对沉积物进行断代分析,具有一定的可行性;牛轭湖河/湖沉积相转变未对沉积物铅元素的非自然因素富集产生影响,说明铅污染具有较广的“暴露面”。     

新疆伊犁河谷沙漠沉积不同粒径组分的地球化学元素分布特征

本文通过对伊犁河谷西部塔克尔莫乎尔沙漠内的可克达拉（TKP）剖面典型层位样品 的不同粒级组分地球化学元素分析,探究西风环流控制的沙漠沉积区元素特征和化学风化指标 在不同粒级组分中的分布特征。研究结果表明TKP 剖面Na 和Sr 元素趋向于在粗粒级中富集; Fe、Mg、Al、Rb 元素趋向于细粒级中富集,K 元素含量随粒径增大先升高再降低,16 ~ 32 μm 粒 级处出现谷值;Ti 元素含量与粒度关系不明确。CIA、Rb/Sr 随粒级增大逐渐降低,Na2O/Al2O3、 Na2O/K2O、K2O/Al2O3 随粒级增大逐渐升高。TKP 剖面地球化学元素和比值在<2 μm、2~16 μm、 16 ~32 μm 细粒级组分不同粒级间变化较为剧烈,32~ 63 μm、63~125 μm、>125 μm 粗粒级组分 变化则不明显,而且粗粒级组分在剖面中的变化也比较稳定。剖面整体风化程度较弱,因此这 种现象可能是物源不统一造成的,为塔克尔莫乎尔沙漠具有物源多样性特点的观点提供了地球 化学元素方面的证据。     

Oxidative capacities of size-segregated haze particles in a residential area of Beijing

The frequent haze days around the Chinese capital of Beijing in recent years have aroused great attention owing to the detrimental efects on visibility and public health. To discover the potential health efects of the haze, oxidative capacities of airborne particles collected in Beijing during haze and clear days were comparably assessed by a plasmid scission assay. Eleven water-soluble trace elements(As, Cd, Cr, Cu, Mn, Ni, Pb, V, Se, Tl, and Zn) in the size-segregated airborne particles were quantitatively analyzed by inductively coupled plasma mass spectrometry, and most of the watersoluble trace elements were found to mainly concentrate in the fine particle size of 0.56–1.0 μm. In comparison with clear days, the mass concentrations of 11 analyzed water-soluble trace elements remarkably increased during haze days, and the oxidative capacities determined by the plasmid scission assay were markedly elevated accordingly during the haze days under the same dosage of particles as for those during clear days. Water-soluble trace elements in airborne particles, such as Cu, V, and particularly Zn, were found to have significantly positive correlations with the plasmid DNA damage rates. Because Cu, V, and Zn have been considered as bioavailable elements, the evident increase of these elements during haze days may be greatly harmful to human health.     

Finite element modeling of microstructural changes in dry and cryogenic machining of AZ31B magnesium alloy

Unsatisfactory corrosion resistance is one of the major disadvantages of magnesium alloys that impede their wide application. Microstructural changes, especially grain sizes, of Mg alloys have significant influence on their corrosion resistance. Cryogenic machining was reported to effectively induce grain refinement on Mg alloys and has a potential to improve their corrosion resistance. It is important to model these changes so that proper machining conditions can be found to enhance the corrosion rate of Mg alloys. In this paper, a preliminary study was conducted to model the microstructural changes of AZ31B Mg alloy during dry and cryogenic machining using the finite element (FE) method and a user subroutine based on the dynamic recrystallization (DRX) mechanism of Mg alloys. Good agreement in terms of grain size and affected layer thickness was found between experimental and predicted results. A numerical study was conducted using this model to investigate the influence of rake angle on microstructural changes after cryogenic machining.     

Determining work-brush interface temperature in magnetic abrasive finishing process

Magnetic abrasive finishing (MAF) is a process in which the work surface is finished by removing the material in the form of micro chips by magnetic abrasive particles (MAPs) in the presence of magnetic field in the finishing zone. During the MAF process, the frictional heat is generated at the workpiece surface due to the rubbing action of magnetic abrasive particles with the work surface. The order of temperature rise is important to study, as finishing mechanism and surface integrity of work materials depend upon it. The measurement of temperature distribution during MAF operation at the interface of work piece and flexible magnetic abrasive brush (FMAB) interface is difficult. In the present analysis, finite element based ANSYS software has been used to model and simulate magnetic field distribution, magnetic pressure and temperature distribution at work-brush interface during the process. In this work the maximum magnetic flux density has been simulated of the order of 0.223 T at 0.91 A of current in electromagnet coil. Magnetic pressure on MAPs due to magnetic field of electromagnetic coil has been calculated to evaluate the frictional heat flux generated at the work-brush interface. Transient thermal analysis of workpiece domain has been performed to predict the temperature rise due to frictional heat flux. The predicted temperature on work-brush interface was found in the range of 34–51 °C. The developed simulation results based on FEA have been validated with experimental findings.     

过程安全管理要素——标准符合性研究

介绍了标准符合性要素的关键控制点和CCPS对该要素的要求,对比了国内外炼化企业在该要素的做法和差距,提出了建立书面程序、明确负责人、监控变更、合规性评价和培训5个方面的建议。     

海洋环境水下电磁场激励源综述

通过总结海洋环境水下电磁场源的产生机理、基本特性、频带幅值以及观测方法,确定了不同海域普遍存在、影响程度较大并且规律性较强的场源。最终给出具有重要研究价值的典型场源,即海洋大地电磁场、海浪感应电磁场、海流感应电磁场和工频电磁场。     

贵州威宁麻窝山岩溶盆地沉积物的微量元素特征及环境意义

根据贵州威宁麻窝山岩溶盆地沉积物的剖面特征及微量元素特征的分析,探讨了该地区沉积环境的演化。对沉积剖面73个样品的分析结果表明,该区∑REE含量较高,稀土的配分模式为轻稀土元素明显富集、重稀土元素亏损的"右倾型",δEu负异常明显,样品的轻重稀土的分馏程度高。δCe反映了研究区沉积期的氧化还原状态,在HD、G1、N1、G5、N5、G6、N6表现为正异常或无异常,沉积时处于强氧化状态;其他层表现为负异常或无异常,表征沉积期的还原环境。微量元素含量变化特征、∑REE含量以及δCe值都说明了研究区古气候的干冷-温湿的旋回演化特征,自下而上可分为3个阶段,研究区经历2个明显的干冷-温湿大循环和3个干冷-温湿交替的小循环。     

黔中白云岩风化剖面微量元素的地球化学特征

本研究是为了探讨微量元素在化学风化作用下的迁移特征及分布规律并讨论碳酸盐岩地区红色风化壳的物源问题。我们选择了贵州省遵义市新浦镇的一处发育完好的原生白云岩上覆红土剖面作为研究的对象。以Zr作为不活化元素,我们得到以下的认识:1)该白云岩上覆红土剖面是原地形成的淋滤剖面,微量元素的迁移系数在红土剖面中的变化都具有很好的规律性。元素对Nb-Ta、Zr-Hf和Y-Yb的相关性很强,其可以作为上覆土层物质非多来源的证据,而单一物源与下伏岩石高度相关,那么可以推断所研究的土壤来源于下覆碳酸盐岩的风化。2)在整个剖面中,大部分微量元素在风化过程中都表现出富集的特性,尤其在岩-土界面处达到最大化,这显示出了风化淋滤的过程。Nb、Ta、V和Hf是相对不活化的元素。3)轻稀土元素在岩土界面的富集系数是大于重稀土元素的,这表明轻稀土元素在淋滤过程中更易于迁移。此外,铁质壳对相关微量元素有着富集的作用。总之,本次的研究结果对探讨喀斯特地区红土型风化壳的物质来源问题有着重要的指示意义。