硫化纳米零价铁(S-nZVI)对水体中镉的去除研究

由于矿山开采、工业废水排放及农业施肥等人类活动,使得我国镉污染日益突出.本研究采用液相还原法制备硫化纳米零价铁(S-nZVI),研究其对Cd的去除行为.考察了不同硫化剂、合成方法、S/Fe比(物质的量比)及pH对Cd去除的影响,并采用扫描电子显微镜(SEM)、拉曼光谱(Raman)、X-射线衍射(XRD)等技术对反应前后的材料进行表征,结合批实验结果探讨Cd的去除机理.结果表明,采用一步法以硫化钠(Na_2S)为硫化剂合成的S-nZVI对Cd的去除效率远高于其它方法,去除容量可达385.6 mg·g~(-1).反应120 min后,S-nZVI对Cd的去除率随S/Fe比的增加而升高,S-nZVI反应体系受pH影响较小.材料表征结果显示,S-nZVI颗粒由Fe~0、Fe_3O_4、FeS组成,其中,FeS的含量随S/Fe比的升高而增加.S-nZVI对Cd的去除机理主要是Cd将FeS中的Fe置换,与S结合形成稳定的CdS.     

16种蛇鳞的微皮纹分析

对16种蛇鳞的扫描电镜观察表明,蛇类鳞片微皮纹的基本结构是由d约05μm横行排列的小孔和介于小孔间向后延伸的指状突构成背鳞的微皮纹结构有种的特异性同一种蛇的原动物、蛇蜕和药材标本相同部位的鳞片具有相同的微皮纹特征因此蛇鳞的微皮纹特征亦可作为蛇类药材的鉴别依据之一,并以背鳞的微皮纹特征为依据,编制了16种蛇背鳞微皮纹特征检索表。     

拉曼光谱在比较水中杂质浓度的研究

为了比较不同水样品中所含杂质浓度的相对大小,运用激光拉曼光谱的分析方法,测量了四种不同水样品的激光拉曼光谱,同时还测量了蒸馏水的激光拉曼光谱.计算了它们的弯曲振动强度与伸缩振动强度之比,并对测量和计算结果进行了比较和分析.结果表明,水中所舍杂质浓度的相对大小不仅可以从其拉曼谱杂峰和毛刺的多少做定性比较,而且还可以从弯曲振动强度与伸缩振动强度的比值的相对大小做定量比较.这为水质分析提供了新的有效途径.     

铵盐气溶胶对烟气排放连续监测系统颗粒物比对监测的影响研究

利用拉曼光谱对采样后的滤筒进行分析,发现废气中的硫酸铵-硫酸氢铵气溶胶是造成成都市部分企业烟气排放连续监测系统(CEMS)颗粒物比对监测结果不合格的主要原因。通过比较分析得出:在对含硫酸铵-硫酸氢铵气溶胶废气进行颗粒物浓度比对监测时,参比方法(重量法)测定的颗粒物浓度是一定标干采样体积下废气中固体微粒和硫酸铵-硫酸氢铵液体微粒结晶后产生的晶体的总质量,基于光散射法的CEMS颗粒物浓度测试系统测定的颗粒物浓度只是一定标干采样体积下废气中固体微粒的质量,由此导致参比方法测出的颗粒物浓度远大于CEMS测出的浓度,造成比对误差远超出允许值范围。     

基于甲烷氧化菌的城镇污水厂尾水极限脱氮系统构建及机制

好氧甲烷耦合反硝化(AME-D)在城镇污水厂尾水深度脱氮方面具有巨大的应用潜力,研究采用改良型反硝化生物滤池,利用低浓度甲烷构建出AME-D极限脱氮系统.研究发现该系统在间歇式运行方式下,出水中总氮和氨氮的平均浓度能达到1.05 mg·L^-1和0.54 mg·L^-1,其平均去除率分别为94.77%和93.30%.拉曼光谱分析结果显示,由NO^-₃对称伸缩引起的峰明显消失,由醇COH面外弯曲或C—H面外弯曲振动吸收引起峰明显增强,甲烷被氧化形成的中间产物可能主要为醇类物质. 16S rRNA基因测序结果表明,系统中的甲烷氧化菌主要为Methylocystis(0.27%)、Methylosarcina(0.10%)和Methyloparacoccus(0.12%),反硝化菌主要为Pseudomonas(56.92%)、Paenibacillus(3.52%)和Lysinibacillus(3.00%),硝化菌主要为Nitrospira(0.1%),说明AME-D极限脱氮系统的脱氮功能是由好氧甲烷氧化菌、...     

New approaches to characterizing urban air particles in central London

１　ＩｎｔｒｏｄｕｃｔｉｏｎＯｎａｎｉｎｔｅｒｎａｔｉｏｎａｌｓｃａｌｅ，ｔｈｅｎａｔｕｒｅｏｆｕｒｂａｎａｉｒｐｏｌｌｕｔｉｏｎｈａｓｃｈａｎｇｅｄｓｉｇｎｉｆｉｃａｎｔｌｙｏｖｅｒｔｈｅｌａｓｔ５０ｙｅａｒｓ．Ｉｎｔｈｅ１９５０ｓａｎｄ１９６０ｓ，ｔｈｅｍｏｓｔｉｍｐｏｒｔａｎｔｅｎｖｉｒｏｎｍｅｎｔａｌｈｅａｌｔｈｉｓｓｕｅｓｓｔｅｍｍｅｄｆｒｏｍｔｈｅｏｃｃｕｒｒｅｎｃｅｏｆｕｒｂａｎｓｍｏｇｓ，ａｎａｔｍｏｓｐｈｅｒｉｃｃｏｃｋｔａｉｌｃｈａｒａｃｔｅｒｉｚｅｄｂｙｈｉｇｈｃｏｎｃｅｎ…     

镉、铅在玉米幼苗中的积累和迁移--X射线显微分析

用扫描电镜-X射线能谱仪及原子吸收分光光度计,测定经不同浓度镉、铅处理的玉米根、叶中镉、铅的积累。结果表明,铅的积累为皮层>中柱;木质部薄壁组织>导管。镉则相反。铅主要以非共质体途径在根内横向迁移,镉主要以共质体途径在根内横向迁移。原于吸收分光光度计测定表明,镉、铅主要在玉米根内沉积,镉铅复合作用促进了玉米根叶对镉、铅的吸收,镉比铅更易为玉米吸收且更易从根向叶迁移。     

Atmospheric mineral particles collected at Qira in the Taklamakan Desert, China

Aerosol particles were collected in the situation of the widespread dust suspension on 21 February 1991 at Qira in the southern edge of the Taklamakan Desert, western China. The collected particles were examined by a transmission electron microscope equipped with an energy-dispersive X-ray (EDX) analyzer in order to obtain the size and elemental composition of individual mineral particles.On the basis of EDX analyses for 386 particles, mineral particles were present in high number fractions (>99%) of particles in the radius range of 0.1–4 μm. Particles mainly composed of silicates comprised 76% of mineral particles. “Ca-rich” particles were detected in 7% of all the particles. Ca in the particles would be present not only as CaCO₃ but also as an internal mixture of CaCO₃ and CaSO₄. Particles containing halite (NaCl) were detected in number proportions of about 10% and were mainly present in the radius range of 0.5 μm. Some halite particles would be modified by chemical reactions with sulfuric acid.     

Fine structure and X-ray microanalysis of a red macrophyte cultured under cadmium stress

Thalli of the red alga Audouinella saviana were exposed to 600 microM Cd2+ (LC50), 1000 microM Cd2+ and 1500 microM Cd2+ (final concentrations) for 5, 10 and 15 days (each dose) by adding cadmium nitrate to the culture medium. Untreated thalli were set in triplicate as controls for each experiment. Ultrastructural modifications due to cadmium ad/absorption were observed by TEM/SEM electron microscopy. SEM-EDS X-ray microanalysis, definining the accumulation sites, was performed on cryoprepared samples. TEM studies showed striking changes in the plasmalemma of treated algae, which became irregular and convoluted. Electron-transparent exocytic vesicles, possibly related to cell wall polysaccharide synthesis, were observed. The appearance of ribosomes and Golgi bodies, not significantly present in the cytoplasms of untreated cells, suggested enhanced protein and carbohydrate biosynthesis. The cell walls lost their initial grooves and became smooth and thick. More or less electron-dense vesicular systems were formed. Electron-dense sphaeroids occurred in the plasmalemma-cell wall interface, in the cell wall itself and in nearby vesicular membrane systems. Many small vacuoles containing large metal complexes were formed. Complexes were then sequestered into a large vacuole. SEM observations demonstrated that the cell wall and the membrane systems were the most involved in the defense responses. EDS-X-ray microanalysis confirmed the presence of cadmium in these compartments. Chloroplasts, where no Cd2+ signal was detected, were the least affected organelles, showing only a partial disorganization after lengthy exposure to high Cd2+ concentrations.     

城市雾天单个矿物颗粒物理和化学特征

应用场发射扫描电镜(FESEM)和带能谱的扫描电镜(SEM-EDX)对北京冬季雾天和正常天气下收集的4个样品进行研究.雾天中矿物颗粒的数量-粒度分布的峰值出现在0.1～0.3 μm和1～2.5 μm之间,并且发现雾天出现的二次矿物颗粒的数量百分含量(4.67%)高于正常天气条件(0.12%).单个矿物颗粒的EDX能谱显示,雾天和正常天气中单个矿物颗粒的主要化学成分有一定的差别,尤其是S元素.矿物颗粒分为9种不同类型:"富Si"、"富Ca"、"富S"、"富Fe""富Mg"、"富Al"、"富Ti"、"富K"和"富Cl",其中雾天"富Ca"中55%的颗粒含有Ca(50%±1.2%)和S(37%±1.6%),"富S"中72%的颗粒含有S(44%±1.5%)和Ca(33%±2%),说明了雾天中绝大部富集S的颗粒物中同时富集Ca,这在一定程度上说明了北京市大气中这些含Ca的碱性矿物对雾水酸性有一定的缓冲作用.雾天样品中S/Ca的平均比值为6.11,如果以冬季正常天气条件下S/Ca的均值0.73为背景值,雾天中S/Ca的比值是冬季正常天气的8倍,可见雾天中颗粒物表面的硫化现象相当严重,同时也显示出雾天SO2向硫酸盐的转化率比较高.