Enhancement of nitric oxide decomposition efficiency achieved with lanthanum-based perovskite-type catalyst

Direct decompositions of nitric oxide (NO) by La_0.7Ce_0.3SrNiO₄, La_0.4Ba_0.4Ce_0.2SrNiO₄, and Pr_0.4Ba_0.4Ce_0.2SrNiO₄ are experimentally investigated, and the catalysts are tested with different operating parameters to evaluate their activities. Experimental results indicate that the physical and chemical properties of La_0.7Ce_0.3SrNiO₄ are significantly improved by doping with Ba and partial substitution with Pr. NO decomposition efficiencies achieved with La_0.4Ba_0.4Ce_0.2SrNiO₄ and Pr_0.4Ba_0.4Ce_0.2SrNiO₄ are 32% and 68%, respectively, at 400 °C with He as carrier gas. As the temperature is increased to 600 °C, NO decomposition efficiencies achieved with La_0.4Ba_0.4Ce_0.2SrNiO₄ and Pr_0.4Ba_0.4Ce_0.2SrNiO₄, respectively, reach 100% with the inlet NO concentration of 1000 ppm while the space velocity is fixed at 8000 hr^?1. Effects of O₂, H₂O_(g), and CO₂ contents and space velocity on NO decomposition are also explored. The results indicate that NO decomposition efficiencies achieved with La_0.4Ba_0.4Ce_0.2SrNiO₄ and Pr_0.4Ba_0.4Ce_0.2SrNiO₄, respectively, are slightly reduced as space velocity is increased from 8000 to 20,000 hr^?1 at 500 °C. In addition, the activities of both catalysts (La_0.4Ba_0.4Ce_0.2SrNiO₄ and Pr_0.4Ba_0.4Ce_0.2SrNiO₄) for NO decomposition are slightly reduced in the presence of 5% O₂, 5% CO₂, or 5% H₂O_(g). For durability test, with the space velocity of 8000 hr^?1 and operating temperature of 600 °C, high N₂ yield is maintained throughout the durability test of 60 hr, revealing the long-term stability of Pr_0.4Ba_0.4Ce_0.2SrNiO₄ for NO decomposition. Overall, Pr_0.4Ba_0.4Ce_0.2SrNiO₄ shows good catalytic activity for NO decomposition.

Implications: Nitrous oxide (NO) not only causes adverse environmental effects such as acid rain, photochemical smog, and deterioration of visibility and water quality, but also harms human lungs and respiratory system. Pervoskite-type catalysts, including La_0.7Ce_0.3SrNiO₄, La_0.4Ba_0.4Ce_0.2SrNiO₄, and Pr_0.4Ba_0.4Ce_0.2SrNiO₄, are applied for direct NO decomposition. The results show that NO decomposition can be enhanced as La_0.7Ce_0.3SrNiO₄ is substituted with Ba and/or Pr. At 600 °C, NO decomposition efficiencies achieved with La_0.4Ba_0.4Ce_0.2SrNiO₄ and Pr_0.4Ba_0.4Ce_0.2SrNiO₄ reach 100%, demonstrating high activity and good potential for direct NO decomposition. Effects of O₂, H₂O_(g), and CO₂ contents on catalytic activities are also evaluated and discussed.     

Seedling Biomass Partition and Water Use Efficiency of Switchgrass and Milkvetch in Monocultures and Mixtures in Response to Various Water Availabilities

Seedling biomass and allocation, transpiration water use efficiency (TWUE), and species competition between switchgrass (Panicum virgatum L.) and milkvetch (Astragalus adsurgens Pall.) were investigated in a pot-cultivated experiment under different levels of water availability. The experiment was conducted using a simple replacement design in which switchgrass and milkvetch were grown in growth chamber with ten seedlings per pot, in three combinations of the two species (0:10, 5:5 and 10:0). Five water treatments included sufficient water supply (HW), gradual soil drying from HW (DHW), moderate water stress (LW), gradual soil drying from LW (DLW), and re-establishment of LW conditions after 12 days of drying from LW (RLW). Water treatments were applied over a 15-day period. Biomass production and its partitioning, and TWUE were determined at the end of the experiment. Species competitive indices (competitive ratio (CR), aggressivity (A) and relative yield total (RYT)) were calculated from the biomass dry weight data for shoots, roots and total biomass. Water stress significantly reduced seedling biomass production but increased root:shoot ratios in both monocultures and mixtures. In the RLW treatment, only switchgrass monocultures displayed compensatory biomass production and TWUE, while both species demonstrated compensatory growth in the mixture. Switchgrass was the dominant species and much more aggressive than milkvetch in the LW treatment, while in the other four treatments milkvetch was the dominant species as measured by the positive value of aggressivity and higher values of CR. The total biomass RYT values of the two species were higher than 1.0, indicating some degree of resource complimentarity. In the two-species mixture, although the biomass production was lower than that of milkvetch in the monoculture, there was better TWUE, especially under low and fluctuating water availability.     

改进型曝气生物滤池对生活污水氮去除的影响

采用下向流中部曝气的运行方式,对生活污水进行了处理,考察了气水比、有机负荷对生物滤池的去除效果及其沿程生化特性。结果表明:水力停留时间为8 h,气水比为10∶1条件下可获得最佳的处理效果,COD、TN和NH4+-N的平均去除率分别为92.5%、48.6%和69.4%。进水有机负荷增加,COD和NH4+-N的去除率下降,TN的去除率可达60.5%。结合理论分析,对脱氮性能进行了探讨。     

环境图书的特点与管理对策

环境图书是以环境保护为主要内容的图书，其发展经历了上世纪七十年代的起步阶段，八十年代的发展阶段及九十年代以来的扩充阶段，具有综合性强、种类繁多、实用性强、发展迅速等特点。因此应采取集中管理，尽快借阅，外借与阅览并在，提供咨询服务等对策。     

Catalytic removal of phenol from gas streams by perovskite-type catalysts

Three perovskite-type catalysts prepared by citric acid method are applied to remove phenol from gas streams with the total flow rate of 300 mL/min, corresponding to a GHSV of10,000/hr. LaMnO_3 catalyst is first prepared and further partially substituted with Sr and Cu to prepare La_(0.8)Sr_(0.2)MnO_3 and La_(0.8)Sr_(0.2)Mn_(0.8)Cu_(0.2)O_3, and catalytic activities and fundamental characteristics of these three catalysts are compared. The results show that phenol removal efficiency achieved with La_(0.8)Sr_(0.2)Mn_(0.8)Cu_(0.2)O_3 reaches 100% with the operating temperature of 200°C and the rate of mineralization at 300°C is up to 100%, while the phenol removal efficiencies achieved with La_(0.8)Sr_(0.2)MnO_3 and LaMnO_3 are up to 100% with the operating temperature of 300°C and 400°C, respectively. X-ray photoelectron spectroscopy(XPS) analysis shows that the addition of Sr and Cu increases the lattice oxygen of La_(0.8)Sr_(0.2)Mn_(0.8)Cu_(0.2)O_3, and further increases mobility or availability of lattice oxygen. The results indicate that La_(0.8)Sr_(0.2)Mn_(0.8)Cu_(0.2)O_3 has the best activity for phenol removal among three catalysts prepared and the catalytic activity of phenol oxidation is enhanced by the introduction of Sr and Cu into LaMnO_3. Apparent activation energy of 48 k J/mol is calculated by Mars–Van Krevelen Model for phenol oxidation with La_(0.8)Sr_(0.2)Mn_(0.8)Cu_(0.2)O_3 as catalyst.     

苍耳子的化学成分

苍耳子(Fructus Xanthii)是常用中药,主要用于慢性鼻炎的治疗,有一定的毒性.为明确苍耳子产生生物活性的物质基础,通过溶剂萃取、正、反相反复硅胶柱色谱及MCI柱色谱等方法,对苍耳子80%甲醇提取物进行分离纯化,用质谱、核磁共振谱等方法进行结构鉴定.从正丁醇萃取物中分离鉴定7个化合物:阿魏酸(1)、咖啡酸(2)、绿原酸(3)、4-O-咖啡酰奎宁酸甲酯(4)、6,7-二甲基-1,4-二氢-2,3-喹喔啉二酮(5)、咖啡酸胆碱酯(6)和4′-O-二氢红花菜豆酸钠盐-β-D-葡萄糖苷(7).其中,化合物4~7为首次从该植物中分离得到.图1参10     

沉积物中磷形态及影响其释放的环境因素研究进展

磷是控制水体富营养化最关键的营养物质,在外源磷得到控制之后,内源磷通过各种复杂过程再次进入水体,成为水体富营养化的主要磷污染源。目前,国内外对底泥磷的相关研究已非常多,但缺乏系统的整理和总结。从底泥磷的形态和影响其释放的环境因素2个方面进行了系统总结,介绍了底泥磷的主要形态、释放机制,分析了环境因素对于底泥磷释放的影响。     

城市森林大气PM2.5中水溶性无机离子沉降特征

森林被誉为"地球之肺",在防霾治污方面有其独特不可替代的作用,不同树种沉降PM_2.5的功能有很大差别.本文选取代表性城市森林——奥林匹克森林公园为研究对象,设置垂直监测塔观测大气PM_2.5的浓度垂直分布,以考察不同季节城市森林对PM_2.5中各组分的影响.在冬季、春季和夏季各采集PM_2.5样品,分析并计算PM_2.5中Na⁺、NH₄⁺、K⁺、Mg2⁺、Ca2⁺、Cl^-、NO₃^-和SO₄^2-等典型水溶性无机离子的浓度.结果表明,PM_2.5中水溶性无机离子总浓度呈规律性变化特征:冬季((56.90±27.38)μg·m-3)>春季((46.69±12.24)μg·m^-3)>夏季((23.16±8.75)μg·m^-3).其中SO₄^2-和NO₃^-浓度和占PM_2.5主要水溶性无机离子总浓度的50%以上.3个季节中,除冬季外,在春季和夏季,8种离子有明显的垂直方向上的沉降,夏季的沉降速率高于春季,但是春季由于大气颗粒物浓度高,沉降通量高于夏季.NO₃^-和SO₄^2-垂直方向的沉降量在所有可溶性无机离子中最高.植被密度、叶面积指数、气象条件等因素对于PM_2.5的沉降特征有明显影响.     

辽宁典型海域表层海水中在用化学农药浓度水平与潜在生态风险

采用超高效液相色谱-串联质谱仪分析了辽宁典型海域表层海水中14种在用化学农药（current use pesticides,CUPs）浓度水平,探讨了CUPs的可能来源,并评估其潜在生态风险.结果表明,辽宁典型海域表层海水中共检出7种CUPs,总浓度水平范围为16.7~176.1 ng·L^-1,高值区域主要位于河流入海口,辽东湾西部海域CUPs检出浓度普遍高于黄海东北部海域.除草剂阿特拉津（atrazine）和杀菌剂三唑醇（triadimenol）在检出7种CUPs中占比最高,贡献率分别为56.0%和34.5%.源解析表明,6种CUPs可能来源于农田退水等径流输入和生产化学农药的工厂废水排放等,水果种植业则可能是单一组分乙草胺（acetochlor）的重要贡献源.除草剂阿特拉津和乙草胺对研究海域微藻存在中等-高风险,7种CUPs对无脊椎动物和鱼类的风险均处于较低水平.     

Non-UV germicidal activity of fresh TiO2 and Ag/TiO2

Fresh TiO2 was found to possess a strong germicidal activity even without UV irradiation. Live Yeast (Saccharomyces cerevisiae) cells in contact with fresh TiO2 were found deformed and dead after 15 min contact. The cause of germicidal activity was discussed from the observed cell deformation, lysis and increased absorption at 1680 cm-1 in FT-IR spectra of the affected cells, which proved the oxidizing effect of fresh TiO2 to cells. The deformation caused by the stretching of cell wall and pressure built-up inside the cell, led to cell burst and release of intracellular materials. The degree of cell deformation was found positively related with the wetting property of TiO2. Cells are negatively charged, for Gram-negative cell (thinner cell wall), a higher germicidal effect was observed than Gram-positive cells. The germicidal effect of TiO2 gradually decreases after exposure to air at room temperature, as the wetting property decreases. This kind of germicidal activity was more effective compared to other germicidal process such as UVA/TiO2 or Ag+. This shed light on designing new germicidal material either maintained by visible light irradiation, or by oxidation effect generated by reactive oxygen species.