Comparison of PAH Levels and Sources in Pine Needles from Portugal,Spain, and Greece

The main objective of this work was to assess and compare the levels, patterns, and sources of contamination of 16 polycyclic aromatic hydrocarbons (PAHs) between Portugal, Spain, and Greece (in the island of Crete). A total of 9 sampling sites were chosen (4 in urban and 5 in non-urban areas) in each country and pine needles from the Pinus pinea L. species were collected. Although the mean total PAH levels was similar in the three countries (279 ± 236 ng g^?1 for Portugal, 294 ± 258 ng g^?1 for Spain, 301 ± 253 ng g^?1 for Greece, all dry weight) and, in general, 3-ring and 4-ring PAHs were predominant (being phenanthrene consistently the most abundant), there were some visible differences in the aromatic ring patterns and possible sources between the three regions. Source apportionment was done using PAH ratios (Phen/Ant and Flt/Pyr crossplots) and reflected mixed petrogenic and pyrogenic sources. Furthermore, Principal Component Analysis (PCA) clearly separated the urban and the non-urban sites and all three countries, which reinforces that the sources of contaminations vary in each case and the suitability of pine needles for trans-boundary biomonitoring of PAHs.     

超微粒介孔分子筛Ti-MCM-41的合成及应用

超微粒分子筛;苯乙烯;催化氧化;超微粒介孔分子筛Ti-MCM-41的合成及应用     

Photocatalytic Effects of Rutile Phase TiO2 Ultrafine Powder with High Specific Surface Area Obtained by a Homogeneous Precipitation Process at Low Temperatures

The photocatalytic characteristics of nanostructured TiO₂ ultrafine powder with rutile phase produced using the homogeneous precipitation process at low temperatures (HPPLT) were compared with those of commercial P-25 TiO₂ powder by flame hydrolysis. The TiO₂ powder by the HPPLT showed much higher photoactivity in the removal rate, showing lower pH values in the solution than the P-25 powder when eliminating metal ions such as Pb and Cu from the aqueous metal-EDTA solutions. This can be inferred as the more rapid photo-oxidation or -reduction of metal ions from the aqueous solution, together with relatively higher efficiencies in the use of an electron-hole pair formed on the surface of the TiO₂ particles under UV light irradiation. Also, in the view of the TiO₂ particle morphology, compared to the well-dispersed spherical P-25 particles, the agglomerated TiO₂ secondary particles by the HPPLT consist of acicular typed primary particles with a thickness in the range of 3–7 nm and the primary particles radialize in all directions, which would be more effective to photocatalytic reactions without the large electron-hole recombination on the surface of the TiO₂ particle under UV light irradiation. It can be, therefore, thought that the higher photoactivity of the rutile TiO₂ powder by the HPPLT in the aqueous solutions results mainly from having a larger surface area by the acicular shaped primary particles with very thin thickness and radialization in all directions.     

高能机械球磨法制备V-Ti-O超细微粒催化剂

负载型V2O5/TiO2氧化物催化剂因具有优良的催化性能而广泛地用于烃类选择性氧化[1,2]和氮氧化物选择性催化还原(SCR)[3]. 迄今,所研究的负载型V2O5/TiO2氧化物催化剂大多是采用浸渍法制备的[2,4～6],通过调整催化剂的组成[2,5]、引入适当的助剂组分[2,6]和选择适宜的反应操作条件[2,5]可进一步优化其催化性能.     

均分散球形氧化铕超细微粒的制备和表征

采用尿素分解法制备了均分散球形Eu(OH)CO~3·H~2O超细沉淀粒子,进一步在空气中750℃下焙烧4h,得到了均分散球形氧化铕超细微粒。考察了各种反应条件的影响,获得了最佳的制备条件。用XRD,IR,TEM,TG以及比表面测定等手段对样品进行了表征。     

激光-感应复合加热蒸发-冷凝法制备超微锌粉

提出了一种制备超微粉的新方法,并制作了原型装置。该方法利用激光高频感应复合热源加热金属,以蒸发冷凝的方式获取超微粉。用该方法制取了超微锌粉,产率为12g/min,粉末平均粒径为33.20nm。     

用基态透明的物质进行激光合成超细粉

用ＴＥＡ ＣＯ２激光的被原料吸收谨不被吸收的不同谱线辐照几种物质,如四甲基硅烷,三甲基氯寺烷,六甲基二硅胺烷等,比较其反应情况与产物的异同。认为对于振动基态透明的物质,可以由激光引发气体级联电离的机制生成高活性的低温等离子体从而诱发化学反应,同样可以合成超细粉,而不爱物质吸光性的限制。因此激光方法的原料范围可大为拓宽。本文对影响这类反应和产物的诸因素和激光功率密度、外电场、稀释气体、原料分子的化学     

超细铜粉的化学镀锡及其抗氧化性能研究

以水合肼还原法制备出平均粒径约1μm的超细铜粉,并对其进行化学镀锡。研究了镀锡层对复合粉末微观形貌及抗氧化性能的影响。结果表明:镀覆质量分数50%的锡后,复合粉末平均粒径有所减小,但在空气中的氧化起始温度从120℃提高到220℃,与镀银层相比,镀锡层在较低温度区间对铜粉抗氧化具有优势。     

钛酸钡微晶粉粒的热刺激电流

研究了铁电微晶粉粒的热刺激电流及其铁电相变。对三种不同化学成分的钛酸钡粉料与硅油的混合物进行了热刺激电流测量。钛酸钡粉粒与硅油的混合物有很明显的热刺激电流(TSC)且表现出和铁电相变有关的明显的峰,显示出与粒径存在一定的关系;得出了样品的表观极化强度曲线。证明了当粉料与硅油混合后,用介电谱观测不到的粉料的铁电–顺电相变,用 TSC 方法可以观察到。     

水性体系中超细镍粉的液相还原制备

采用快捷、温和的液相还原法,在水溶液中,以氢氧化钠为pH值调节剂,利用水合肼的还原作用将氯化镍还原得到超细镍粉．利用扫描电镜（SEM）及X射线衍射（XRD）的表征手段研究了反应条件对超细镍粉微观结构的影响．结果表明,所得到的产物是纯的面心立方结构的镍材料,颗粒的尺寸介于200～500nm之间,且分布较为均匀．