袋式除尘器进气均布板结构参数对气流分布的影响分析

针对袋式除尘器的进气均布板主要结构参数对气流分布影响的问题,采用正交试验方法进行CFD模拟试验设计,并以气流速度相对均方根σ值作为气流均匀性的评价指标。研究结果给出了σ与板数n、板长L、挡板上端距灰斗顶部截面高度ΔH、挡板前后偏角θ及过滤风速v之间的函数关系式。表明适当增加n、增大ΔH和θ、减小L、降低v,可以提高进气流分布均匀程度,影响进气均匀分布程度的排序为L>θ>n>ΔH>ΔL。     

银川平原主要湖泊湿地水环境现状调查与分析

为了掌握和了解银川平原主要湖泊湿地的水质环境状况,对宁夏沙湖、鸣翠湖、星海湖、阅海湖、鹤泉湖等湿地开展了水质现状调查和分析研究,结果表明,这些湖泊湿地都受到污染,沙湖、星海湖和鸣翠湖的水质受到轻度污染,水质根据地表水环境质量标准分类为IV类,鹤泉湖和阅海湖的水质受到中度污染,水之类别为V类。该研究为湿地资源保护与合理利用提供科学依据,对宁夏经济协调发展提供科技支撑。     

Photodegradation of amoxicillin by catalyzed Fe3+/H2O2 process

Three oxidation processes of UV-Fe³⁺(EDTA)/H₂O₂ (UV: ultraviolet light; EDTA: ethylenediaminetetraacetic acid), UV-Fe³⁺/H₂O₂ and Fe³⁺/H₂O₂ were simultaneously investigated for the degradation of amoxicillin at pH 7.0. The results indicated that, 100% amoxicillin degradation and 81.9% chemical oxygen demand (COD_Cr) removal could be achieved in the UV-Fe³⁺ (EDTA)/H₂O₂ process. The treatment efficiency of amoxicillin and COD_Cr removal were found to decrease to 59.0% and 43.0% in the UV-Fe³⁺/H₂O₂ process; 39.6% and 31.3% in the Fe³⁺/H₂O₂ process. Moreover, the results of biodegradability (biological oxygen demand (BOD₅)/COD_Cr ratio) revealed that the UV-Fe³⁺ (EDTA)/H₂O₂ process was a promising strategy to degrade amoxicillin as the biodegradability of the effluent was improved to 0.45, compared with the cases of UV-Fe³⁺/H₂O₂ (0.25) and Fe³⁺/H₂O₂ (0.10) processes. Therefore, it could be deduced that EDTA and UV light performed synergetic catalytic effect on the Fe³⁺/H₂O₂ process, enhancing the treatment efficiency. The degradation mechanisms were also investigated via UV-Vis spectra, and high performance liquid chromatography-mass spectra. The degradation pathway of amoxicillin was further proposed.     

Visible-light-driven photocatalytic inactivation of bacteriophage f2 by Cu-TiO2 nanofibers in the presence of humic acid

Pathogenic viruses in drinking water are great threats to public health. Visible-light-driven photocatalysis is a promising technology for virus inactivation. However, the existing photocatalytic antiviral research studies have mostly been carried out in single-component systems, neglecting the effect of natural organic matter, which exists widely in actual water bodies. In this paper, electrospun Cu-TiO₂ nanofibers were prepared as photocatalysts, and their photocatalytic antiviral performance in the presence of humic acid (HA) was comprehensively studied for the first time. The properties of the reaction mixture were measured during the reaction. In addition, the safety, reliability and stability of photocatalytic disinfection in the mixed system were evaluated. The results showed that the virus removal efficiency decreased with the increase of the HA concentration. The type of reaction solution, such as PBS buffer solution or water, did not affect the removal efficiency noticeably. Under acidic conditions, the electrostatic forces between photocatalysts and viruses were strengthened, leading to higher virus removal efficiency. As the reaction time went on, the pH value in the solution increased first and then tended to be stable, the conductivity remained stable, and the dissolved oxygen increased first and then decreased. The safety test showed that the concentration of Cu ions released into the solution was lower than specified by the international standards. No photoreactivation was observed, and the addition of HA significantly reduced the reutilization efficiency of the photocatalysts.     

化学反应危害的识别及预防控制

1 问题的提出 化学反应过程常常由于一些非预期的因素,如进料错误、杂质、反应器过热、冷却系统故障、外部火灾和搅拌失效等,使反应偏离正常操作范围,造成异常放热.若此时无法将所产生的热量迅速移除,则可能导致加速反应,形成自加速放热现象.     

Enantiomeric ratios as an indicator of exposure processes for persistent pollutants in human placentas

The enantiomeric ratios (ER) of alpha-HCH and o,p'-DDT ((+)-isomer concentration/(-)-isomer concentration) and o,p'-DDD (first eluting enantiomer/second enantiomer) were investigated in 112 human placentas from Finnish boys collected 1997-2001. Both o,p'-DDD and alpha-HCH showed changes in their ER depending on the total concentration of the compound in the sample. Their ERs are approaching a value close to racemic mixture (ER=1) at high concentrations. At low concentrations they often differ from 1. The relationship between concentration and ER is clearly identified and it has been shown that it is not affected by analytical uncertainty. This relationship appears to be important for assessing tissue- and species-specific exposure and risk and it may indicate whether net uptake or metabolic activity is dominant in exposure for the resulting exposure of the enantiomers.     

珍惜生命

案头有这样一份资料,2003年全国共发生道路交通事故66．7万多起,死亡人数约10万余人,是5年前30万起的一倍多,比5年前死亡近7万人的幅度明显上升。平均每天有285人在车轮下丧生,相当于每天从空中摔下一架大型客机。