碳化硅陶瓷膜管对PM_(2.5)捕集性能的实验研究

PM2.5因其粒径小、吸附能力强、输送距离远、环境危害大,同时捕集困难而成为世界各国共同关注的大气环境问题。以涂氧化铝膜的碳化硅陶瓷膜管(孔隙率28.16%,平均孔径20μm,过滤面积0.28 m2)为过滤元件,搭建了PM2.5捕集的实验装置,对膜管的过滤时间、通量与阻力降的关系以及捕集效率与时间的关系和膜污染控制方面进行了研究。结果表明:随过滤时间增加,通量逐渐减小,阻力降逐渐增大,捕集效率逐渐增大,对PM2.5捕集效率高达99.9%;对膜污染控制参数优化后反吹压强选定为0.8 MPa,反吹间隔时间为10 min,反吹时间为14 s。     

Physical and chemical processes of wintertime secondary nitrate aerosol formation

The UCD/CIT model was modified to include a process analysis (PA) scheme for gas and particulate matter (PM) to study the formation of secondary nitrate aerosol during a stagnant wintertime air pollution episode during the California Regional PM_2.5/PM₁₀ Air Quality Study (CRPAQS) where detailed measurements of PM components are available at a few sites. Secondary nitrate is formed in the urban areas from near the ground to a few hundred meters above the surface during the day with a maximum modeled net increase rate of 4 μg·m^-3·d^-1 during the study episode. The secondary nitrate formation rate in rural areas is lower due to lower NO₂. In the afternoon hours, near-surface temperature can be high enough to evaporate the particulate nitrate. In the nighttime hours, both the gas phase N₂O₅ reactions with water vapor and the N₂O₅ heterogeneous reactions with particle-bound water are important for secondary nitrate formation. The N₂O₅ reactions are most import near the surface to a few hundred meters above surface with a maximum modeled net secondary nitrate increase rate of 1 μg·m^-3·d^-1 and are more significant in the rural areas where the O₃ concentrations are high at night. In general, vertical transport during the day moves the nitrate formed near the surface to higher elevations. During the stagnant days, process analysis indicates that the nitrate concentration in the upper air builds up and leads to a net downward flux of nitrate through vertical diffusion and a rapid increase of surface nitrate concentration.     

溴阻燃剂对肝细胞的毒性

为评价四溴联苯醚(2,2,4,4-tetrabromodipheny lether,PBDE-47)、五溴联苯醚(2,2',4,4',5-pentabromodiphenylether,PBDE-99)、九溴联苯醚(polybrominated dipheny lethers206,PBDE-206)、六溴环十二烷(hexabromocyclododecane,HBCD)、四溴双酚A(tetrabromobisphenol A,TBBPA)对人肝细胞(LO2)的体外细胞毒性。将5种溴阻燃剂与人肝细胞LO2共同培养,采用四甲基偶氮噻唑蓝比色法(MTT法)检测5种溴阻燃剂对LO2细胞的相对增殖率,并按照GB/T16886.5-2003/ISO10993-5:1999标准评价5种溴阻燃剂对LO2的细胞毒性。体外实验表明,5种溴阻燃剂对LO2细胞均具有抑制作用,其中PBDE-47、PBDE-99和HBCD呈现剂量依赖关系。     

Catalytic fast pyrolysis of Kraft lignin with HZSM-5 zeolite for producing aromatic hydrocarbons

Catalytic fast pyrolysis (CFP) of Kraft lignins with HZSM-5 zeolite for producing aromatics was investigated using analytical pyrolysis methods. Two Kraft lignins were fast pyrolyzed in the absence and presence of HZSM-5 in a Curie-point pyrolyzer. Without the catalyst, fast pyrolysis of lignin predominantly produced phenols and guaiacols that were derived from the subunits of lignin. However, the presence of HZSM-5 changed the product distribution dramatically. As the SiO₂/Al₂O₃ ratio of HZSM-5 decreased from 200 to 25 and the catalyst-to-lignin ratio increased from 1 to 20, the lignin-derived oxygenates progressively decreased to trace and the aromatics increased substantially. The aromatic yield increased considerably as the pyrolysis temperature increased from 500°C to 650°C, but then decreased with yet further increase of pyrolysis temperature. Under optimal reaction conditions, the aromatic yields were 2.0 wt.% and 5.2 wt.% for the two lignins that had effective hydrogen indexes of 0.08 and 0.35.     

解决黄河耗氧有机物评价中存在问题的方法探讨--四论黄河耗氧有机物污染评价问题

黄河水泥沙含量高,现行的BOD5、COD和高锰酸盐指数测定方法所测结果常不能真实反映其污染状况．针对上述问题提出在评价黄河水质时,不采用COD、高锰酸盐指数和BOD5的实测值,而采用经分别校正的数值,对COD和高锰酸盐指数而言,应从实测值中扣除由泥沙有机质本底量所产生的那部分数值．对BOD5而言,既可通过改进测试操作解决,也可通过乘以校正系数以恢复测量过程中受泥沙沉淀影响而降低的那部分数值．应用校正公式,通过案例研究,对校正方法的正确性进行了检验．     

粗苯酐与杂醇油综合利用制备增塑剂的研究

在固体酸催化下 ,粗苯酐与杂醇油直接酯化再经减压蒸馏制备邻苯二甲酸C4 ～C5混合酯增塑剂 ,经中试生产表明 ,该工艺技术是可行的 ,苯酐及C4 ～C5醇回收利用率均可达 90 %以上 ,且废水排放量很少。其最佳工艺条件为 :(1)酯化反应　 (C4 ～C5醇 )∶(苯酐 ) =2 6∶1 0 ,催化剂用量为反应物总质量的 1 5 % ,温度 110～ 16 0℃ ,时间 5h ,反应在搅拌下进行 ;(2 )减压蒸馏　蒸馏压力 <2 0kPa。     

V2O5/ACF催化剂用于烟气低温脱硝的研究

采用等体积浸渍法制备V_2O_5/ACF,CuO/ACF和Fe_2O_3/ACF催化剂,在H_2O和SO_2存在下,三种催化剂选择性催化还原(SCR)NO_x的活性依次为V_2O_5/ACF>CuO/ACF>Fe_2O_3/ACF.对V_2O_5/ACF催化剂中V_2O_5担载量、反应温度和反应空速对脱硝活性的研究表明,当H_2O和SO_2存在时,V_2O_5的最佳负载量为0.5wt%,在反应温度为180℃,空速为2000 h~(-1)时,NO转化率可达84%,表明该催化剂具有良好的抗H_2O和SO_2毒化的能力.     

The socially optimal recycling rate: Evidence from Japan

This paper estimates the average social cost of municipal waste management as a function of the recycling rate. Social costs include all municipal costs and revenues, costs to recycling households to prepare materials estimated with an original method, external disposal costs, and external recycling benefits. Results suggest average social costs are minimized with recycling rates well below observed and mandated levels in Japan. Cost-minimizing municipalities are estimated to recycle less than the optimal rate. These results are robust to changes in the components of social costs, indicating that Japan and perhaps other developed countries may be setting inefficiently high recycling goals.     

淡水水生生物对阿特拉津除草剂的敏感度

针对水环境中普遍存在的农药污染问题,以阿特拉津除草剂作为研究对象,梳理、整合阿特拉津对水生生态系统中不同营养级水生生物的急、慢性毒性数据,构建了基于对数-逻辑斯蒂分布的水生生物物种敏感度分布模型,分析并对比了阿特拉津对不同类群和不同区系水生生物急慢性毒性敏感度差异. 结果表明,水生动物和植物、无脊椎动物(包括甲壳类、昆虫类、软体动物和蠕虫类)和脊椎动物(包括鱼类和两栖类动物)对阿特拉津敏感度均存在显著差异. 分析了阿特拉津对不同类群水生生物的HC₅(5%危险浓度)值,其中对水生动物和植物的急性毒性HC₅值分别为4257.94和12.55μg/L,慢性毒性的HC₅值分别为2.47和1.95μg/L;对水生脊椎动物和无脊椎动物的HC₅值分别为7490.31和1611.76μg/L;对甲壳类和鱼类的HC₅值分别为1201.16和6639.90μg/L. 在保护95%的物种水平下,不同类群试验生物对阿特拉津的敏感度排序为水生植物>水生动物、水生无脊椎动物>水生脊椎动物、甲壳类动物>鱼类. 从统计学角度分析,中国水生动物与北美水生动物对阿特拉津的敏感度差异不显著. 但是,中美两国间相对特有水生动物物种对阿特拉津的敏感度存在一定的差异.