用X射线吸收近边结构谱研究大气颗粒物中元素的种态

大气颗粒物中元素的种态研究,对评价其毒性和污染来源等有很重要的意义。本工作采集了不同地点和不同粒径的大气颗粒物样品,测定了样品中铬、锰、铜和锌的X射线吸收近边结构(XANES)谱,利用该谱分析了这些元素在颗粒物中的种态。结果显示,所采集的样品中铬主要以三价形式存在,锰主要以二价形式存在,铜也以二价形式存在,而锌主要以硫酸盐存在。用质子激发X射线荧光(PIXE)法测定了这些元素在样品中的浓度,观察到不同采样点和不同粒径的颗粒物中金属含量的差别,但未看到种态的这种变化。     

土壤中水分含量对铀系、钍系天然γ能谱影响的分析

本文采用MCNP软件对含有不同水分含量土壤中铀系和钍系天然γ谱进行了模拟计算,并与不同水分含量土壤中天然γ能谱的影响实验结果进行比较。通过对模拟和实验结果的分析,得到水分对天然γ谱的影响以及变化特征。     

氮在土壤-作物系统中去向——施氮水平的影响(英文)

利用~(15)N技术在灌溉条件下研究施氮水平(75,150,225kg/hm~2)对冬小麦产量、氮素利用和土壤残留态无机态氮及其有效性的影响。结果表明:75kg/hm~2和150kg/hm~2施氮处理的冬小麦获得最高产量,二者没有显著性差异;而225kg/hm~2处理的冬小麦因过量施氮造成籽粒产量下降,并低于不施氮处理。植株对氮素的利用率随施氮水平的增加而下降,分别为38.5％,32.3％和22.4％。作物收获后发现,225kg/hm~2处理中所施氮的46％仍存在于50cm表土层中,高于其它施肥水平的处理。试验中仍有30.2％～36.7％的化学氮素通过各种途径损失而影响环境。在作物收获后,225kg/hm~2处理的土壤无机氮含量最高,并在玉米后效试验中获得最高产量,但土壤中较高的无机氮含量增加了对地下水污染的可能性。     

应用S~(35)研究硫在加拿大杨生长地区土壤(褐色土)中的移动

一、前言硫在植物生长中是一个很重要的元素,某些植物(十字花科)的需硫量每公顷可达80公斤,而杨树等速生用材树种(Populus sp.)的生长,其需硫量(每百克干物质中含S量为0.3克以上)也是较多的。在试验地区土壤中硫的含量是不多的(见表1),而可溶性SO_4~=的含量更少(见表1),因此在上述这样不同性质的土壤中研究硫的移动与分布,对速生用材林木生长来讲     

污染土壤颗粒中钚的结合形态

在我国北方某处荒漠土中掺入氧化钚后制备模拟土壤,湿法粒度分级后,利用改进的Tessier连续提取法研究各粒级土壤颗粒中钚的结合状态,以评价在假想的污染状况下钚在该类区域土壤中的迁移性.结果表明,钚与土壤的结合主要为有机结合态和残渣态(73％～96％).各粒级中钚的结合状态与土壤颗粒有机质及伊利石含量呈现良好的线性关系....     

铀表面状态的变角度XPS研究

采用变角度XPS(X射线光电子谱)技术研究了贫铀的初期氧化过程,获取了金属态贫铀表面U4f和O1s谱峰以及价带的XPS谱.研究结果表明变角度技术对金属铀表面初期的氧化过程揭示得更为详细,而且,金属铀表面外围电子只有离域态性质,未出现局域态,并对比文献中关于"U/基材"体系的实验结果进行了讨论.通过比较15°、45°和85°分析角度下O1s与U4f的XPS谱峰强度比值随时间的变化关系,观测到氧和铀的谱峰强度比值存在明显的差异,表明变角度技术可很好地应用于处于超高真空中的金属铀表面在初期氧化过程中的研究.     

结合XANES和IC技术测量大气颗粒物中硫的形态分布及其含量

结合XANES和IC技术定量分析大气颗粒物中硫的含量及其形态分布.先通过硫的K边XANES分析得到样中硫元素的价态分布,从而得各价态硫的相对含量(原子数比值);再用IC技术测量其中可溶性SO42-的绝对含量,近似得到+6价硫的绝对含量;最后反推出硫元素的总含量及各个价态分布.结果表明,上海沿海地区大气颗粒物PM2.5中...     

微波非热效应对有机硫化合物结构的影响

为探究微波辐照脱除煤中有机硫的作用机理以及影响程度,通过核磁共振氢谱、红外光谱和激光共聚焦显微拉曼光谱技术,研究了微波非热效应对有机硫模型化合物结构性能的影响。红外光谱测试说明,微波辐照有机硫化合物存在非热效应并影响化学键的键能分布、基团的振动强度和稳定性,但仅限于分子的极化机制,不会破坏分子中原有的化学键也不会生成新的化学键和基团;核磁共振氢谱揭示非热效应影响了模型化合物分子内部的电子云密度分布和磁环境,对含硫化合物产生的双重极化作用既可改变微观的电子或原子极化,也可改变分子固有偶极矩的取向;显微激光拉曼光谱证明非热效应可有效极化含硫键,使之振动强度减弱,从而有助于有机硫的微波辐射脱除。     

用高能加速电子束辐照研究细胞色素b_5还原酶的氧化还原反应机制

本文介绍了用高能加速电子束研究细胞色素b_5还原酶的氧化还原反应机制。我们用高能加速电子束照射溶液时产生的水合电子束还原氧化态的细胞色素b_5还原酶,得到了既不是氧化态又不是还原态的新的吸收光谱,从而认为在该酶的氧化态和还原态之间还存在着中间态。     

用穆斯堡尔谱研究Fe-Mo/Al_2O_3加氢脱硫催化剂的物相组成及(Fe-Mo-S)活性相

对氧化态和硫化态的Fe-Mo/Al_2O_3加氢脱硫催化剂进行了穆斯堡尔谱的研究,并结合噻吩脱硫活性测试和XRD分析探讨了催化剂的物相组成及活性相。实验结果表明,不同Fe/Mo原子比的催化剂基体样品,其穆斯堡尔谱主要由钼酸铁Fe_2(MoO_4)_3的双峰和α-FeOOH的双峰以不同比例叠加而成。负载于氧化铝上后,穆斯堡尔谱产生明显变化,表明其间存在着强烈的相互作用。催化剂硫化后,得到Fe_(1-x)S的磁分裂谱,此外在中间部分还叠加了一个δ=0.35mm/s、△=0.78mm/s的双蜂。由于这组双峰的出现是以催化剂中Mo的存在为条件,     

红绿彩瓷之釉上彩的XAFS研究

红绿彩瓷是一种低温釉上彩瓷,从结构层次探讨其釉上红彩、绿彩、黄彩的呈色机理一直是古陶瓷研究的空白。采用X射线吸收精细结构(X-rayabsorption fine structure,XAFS)方法,测试分析红绿彩瓷中的红彩、绿彩和黄彩。结果表明,红彩中致色元素Fe主要为+3价,其局域结构与Fe2O3相近,最近邻配位为扭曲的八面体结构。透射电子显微分析证实其物相为氧化铁晶体。黄彩中致色元素Fe主要存在+2价和+3价,绿彩中致色元素Cu主要为+2价,两者均处于无序度较高的局域环境中,最近邻配位为O原子。     

Determination of Cr(VI) in wood specimen: A XANES study at the Cr K edge

The content of chromium in different oxidation states in chromium-treated wood was studied with XANES (X-ray absorption near-edge structure) measurements at the Cr K absorption edge. It could be shown that wood samples treated with Cr(VI) (pine and beech) did still contain a measurable content of Cr(VI) after four weeks conditioning. If such wood samples were heat exposed for 2 h with 135 °C prior conditioning, Cr(VI) was no longer detected by XANES, indicating a complete reduction to chromium (III).     

Depth profile of chemical states of alloying elements in oxide layer of Zr-based alloys

To understand the basic oxidation kinetics of alloying elements which is considered to be strongly related with the corrosion and hydrogen pickup, the depth profiles of chemical states of alloying elements (Cr and Fe) were measured in the oxide layer of Zr-0.5Sn-1.0Cr-0.5Fe alloys. The depth profiles were obtained by combinations of a surface-sensitive XANES and an extremely low energy Ar ion sputtering. The XANES measurements revealed that the chemical states of alloying elements (Fe and Cr) varied with the depth in the oxide layer. Especially in the oxide layer formed in steam, a decrease of the fractions of oxidation states was significant rather than that in LiOH solution. In the oxide layer formed in steam, the oxidation rate of chromium was faster than iron by a factor of approximately 2.     

AN INAA STUDY ON SOIL BACKGROUND VALUES OF U,Th AND REE IN CHINA

The background values of elements in soil have been investigated by INAA. The contents of 8 REE (La, Ce, Nd, Sm, Eu, Tb, Yb and Lu), U and Th in 364 top soil samples (A horizon) in China were determined by INAA. The samples were collected from some typical areas in China and covered main soil types of these areas. The background values of above elements in soil of the different areas and the whole soil studied in China are reported in present paper. The distribution characteristics of REE, U and Th in soils are also discussed.     

利用石生苔藓中硫同位素示踪大气硫源的变化规律

为探讨石生苔藓硫同位素组成特征对区域性大气硫源的指示作用,连续两年采集鄱阳湖生态经济区内的石生苔藓样品,测定δ³⁴S值;并结合已有的雨水、煤的硫同位素值等相关研究数据进行对比分析。样品δ³⁴S值均偏正,平均为+4.9‰,取值范围为+1.9‰~+9.6‰;石生苔藓δ³⁴S值与空气中SO₂浓度呈负相关关系;南昌、抚州两市苔藓δ³⁴S值的取值范围与其对应城市大气降水δ³⁴S值的变化区间相接近;研究区内土壤相对富集重硫,且土壤中可溶性硫主要受大气硫沉降影响。结果表明,石生苔藓的硫同位素组成对区域性大气硫源具有指示意义,鄱阳湖生态经济区大气硫沉降的硫源主要来自人为成因硫和生物成因硫,可能还有远距离传输硫等其他硫源的影响。     

Chemical effects in the Kβ X-ray emission spectra of sulfur

In this work our previous study about chemical effects in the K spectra of S compounds employing high-resolution X-ray spectroscopy has been extended to the Kβ emission spectra. The measurements were performed with a wavelength dispersive single crystal spectrometer operated in the von Hamos geometry having an energy resolution comparable to the natural linewidth of the measured Kβ X-ray lines. The target fluorescence was produced by irradiating the samples with the bremsstrahlung from an X-ray tube. The energies and widths of the main components in the Kβ emission spectrum are given for different sulfur compounds (sulfide, sulfite, sulfate). The measured energy shifts between the Kβ lines of the compounds and elemental sulfur are presented as a function of the sulfur oxidation state and compared with the results obtained from the former K measurements.     

哈尔滨燃煤电厂周围土壤放射性水平的分析

煤炭燃烧过程中,放射性核素会不同程度的在飞灰和炉渣中富集,进而随着飞灰和炉渣进入土壤环境中,对土壤造成不同程度的放射性污染。本文以哈尔滨群力燃煤电厂和呼兰燃煤电厂为研究对象,在距电厂1 km范围内布设采样点,每个采样点土壤分3层采样,即A层深度:0～10 cm,B层深度:10～20 cm,C层深度:20～30 cm。利用高纯锗γ谱仪测量土样中的天然放射性核素,分析了燃煤电厂周围土壤样品中²³⁸U、²³²Th、²²⁶Ra、⁴⁰K的含量,并与黑龙江省土壤天然放射性核素测量结果进行了比较。结果表明,在群力电厂和呼兰电厂1 km范围内周围土壤中,除了天然放射性核素²³⁸U以外,其他3种核素含量都未超出全省含量最大值,其中核素²³²Th的含量甚至低于全省大部分地区;燃煤电厂的长期运行给土壤环境带来了一定的放射性影响,土壤本底的放射性核素含量发生了一些变化,这种变化在呼兰电厂周围的土壤中表现得更为明显,但是并未超出国家规定的标准,污染程度在可接受的范围内。     

Evaluation of Radon in Soil Gas and Natural Radioactivity in Surface Soil of Kinki District,Japan

Radon and its progeny are an important part of natural environmental exposure to radiation. However, little information is available about the radon contents of soil gas. We carried out a survey of radioactivity, focusing on ²²²Rn-concentrations in soil gas in parts of western Japan. Fifty nine samples in soil gas from 4 Prefectures of the Kinki district were analyzed with a liquid scintillation counter after the trapping of radon in soil gas into a toluene based-scintillation cocktail, together with 19 samples of interest from karst and uranium mining sites in another two Prefectures for comparison. The cumulative frequency of the ²²²Rn-concentrations in soil gas of the Kinki district showed a log-normal distribution. The average content was found to be 11.9kBqm^?3 (arithmetic mean) and 7.5kBqm^?3 (geometric mean). A maximum concentration of radon in soil gas, 2.1 MBqm^?3 was found at the marker of the Ningyo uranium mining site. Surveys of natural radioactivity in soil were also carried out with a Ge(Li) detector to determine the concentrations in soil, mainly focusing on uranium and thorium series. The radon concentrations in soil gas were weakly correlated with those of uranium series in soils. There were no great differences vertically in the natural radioactivity in soils within 1 m, but a difference by one order of magnitude was found in soils horizontally even in the residence area of the Kinki district.     

Investigation on oxidation states of rhenium in Re-HEDP

The oxidation states of rhenium in Re-HEDP (hydroxyethylidene diphosphonate) were measured by the methods of extraction and potentiometric titration. The oxidation state of rhenium in Re-HEDP was mostly +4 valence, and the Re(IV)-HEDP was oxidized to Re( V)-HEDP when it was titrated by 1, at pH 2.0. In the reduction system of Vc+Sn2+, ReO4- was only reduced by Sn2+, but Vc was oxidized earlier than Sn2+ when it was titrated by