垂直风向下双层高架桥理想街谷内空气环境的数值研究

城市街道中复杂的高架桥结构会影响街谷内污染物的扩散.本文利用CFD软件FLUENT,采用标准k-ε方程和组分输运方程,对含双层高架桥的理想街谷内空气流场和CO浓度场进行了数值模拟.结果表明,高架桥破坏了理想街谷内CO浓度分布的爬墙效应,自地面沿高度方向CO浓度逐渐减小,超过每层高架桥面后激增,而后再次降低.双层高架桥改变了污染面源位置和街谷内流场分布.当双层高架桥都处于街谷内部时,来流风垂直于街谷方向自左向右吹送,街谷内涡旋整体结构保持顺时针方向,高架桥附近出现小涡旋,使得CO在街谷内部循环,引起背风面和街谷内CO平均浓度的升高,高架桥的"盖子效应"显著,与无高架桥街谷相比,CO平均浓度升高39.5%.当双层高架的上层高架与街谷建筑顶部持平,下层高架桥位于街谷中部时,街谷内部产生4个较大涡旋,能够显著地提高街谷内地面和背风面CO扩散速率,高架桥的"盖子效应"被破坏;与无高架桥街谷相比,CO平均浓度仅升高8.7%,与双层高架桥都处于街谷内相比,CO平均浓度降低22.1%,为城市多层高架桥建设提供了参考依据.     

成都市街道地表物中的重金属

本文通过对成都市７４ｋｍ＾２研究区域２１个采样点１００天连续采样获得的地表物样品进行分析测主式，获得３６个元素的含量情况，其中非金属元素３个，金属元素３３个，除Ｔｉ，Ｐ为地壳的次要元素外，其余均为微量元素。本文着重对重金属污染，重金属粒径分级含量及重金属累积情况进行了较为详细的探讨。     

Assessment of traffic-related air pollution in the urban streets before and during the 2008 Beijing Olympic Games traffic control period

In order to investigate the air quality and the abatement of traffic-related pollution during the 2008 Olympic Games, we select 12 avenues in the urban area of Beijing to calculate the concentrations of PM₁₀, CO, NO₂ and O₃ before and during the Olympic traffic controlling days, with the OSPM model.Through comparing the modeled results with the measurement results on a representative street, the OSPM model is validated as sufficient to predict the average concentrations of these pollutants at street level, and also reflects their daily variations well, i.e. CO presents the similar double peaks as the traffic flow, PM₁₀ concentration is influenced by other sources. Meanwhile, the model predicts O₃ to stay less during the daytime and ascend in the night, just opposite to NO₂, which reveals the impact of photochemical reactions. In addition, the predicted concentrations on the windward side often exceed the leeward side, indicating the impact of the special street shape, as well as the wind.The comparison between the predicted street concentrations before and during the Olympic traffic control period shows that the overall on-road air quality was improved effectively, due to the 32.3% traffic flow reduction. The concentrations of PM₁₀, CO and NO₂ have reduced from 142.6 μg m⁻³, 3.02 mg m⁻³ and 118.7 μg m⁻³ to 102.0 μg m⁻³, 2.43 mg m⁻³ and 104.1 μg m⁻³. However, the different pollutants show diverse changes after the traffic control. PM₁₀ decreases most, and the reduction effect focusing on the first half-day even clears the morning peak, whereas CO and NO₂ have even reductions to minify the daily fluctuations on the whole. Opposite to the other pollutants, ozone shows an increase of concentration. The average reduction rate of PM₁₀, CO, NO₂ and O₃ are respectively 28%, 19.3%, 12.3% and −25.2%. Furthermore, the streets in east, west, south and north areas present different air quality improvements, probably induced by the varied background pollution in different regions around Beijing, along with the impact of wind force. This finding suggests the pollution control in the surrounding regions, not only in the urban area.     

不对称大底板多塔楼隔震结构的地震响应分析

针对不对称大底板多塔楼隔震结构体系,通过建立地震响应的动力分析简化模型,推导出不对称大底板多塔楼隔震结构体系地震作用下的运动方程。对一实际的不对称大底板多塔楼隔震结构进行地震响应仿真分析,探讨塔楼质量偏心率和塔楼质量比对结构周期比、位移比和层剪力比的影响。结果显示,不对称大底板多塔楼隔震结构扭转角主要由隔震层产生;与不隔震结构相比,不对称大底板多塔楼隔震体系的扭转角减小,可取得较好的减震效果;塔楼与底板的位置分布和质量分布会影响体系的扭转效应和减震效果,应尽量使塔楼的质心与底板质心重合,塔楼质量分布均匀,以减小结构的扭转效应,提高减震效果。     

Phosphorus accumulation by bacteria isolated from a ontinuous-flow two-sludge system

In this article, polyphosphate-accumulating organisms （PAOs） from a lab-scale continuous-flow two-sludge system was isolated and identified, the different phosphorus accumulation characteristics of the isolates under anoxic and aerobic conditions were investigated. Two kinds of PAOs were both found in the anoxic zones of the two-sludge system, one of them utilized only oxygen as electron aeceptor, and the other one utilized either nitrate or oxygen as electron aeceptor. Of the total eight isolates, five isolates were capable of utilizing both nitrate and oxygen as electron acceptors to uptake phosphorus to some extent. And three of the five isolates showed good phosphorus accumulative capacities both under anoxic or aerobic conditions, two identified as Alcaligenes and one identified as Pseudomonas. Streptococcus was observed weak anoxic phosphorus accumulation because of its weak denitrification capacity, but it showed good phosphorus accumulation capacity under aerobic conditions. One isolates identified as Enterobacteriaceae was proved to be a special species of PAOs, which could only uptake small amounts of phosphorus under anoxic conditions, although its denitrification capacity and aerobic phosphorus accumulation capacity were excellent.     

Comparing results of cultured and uncultured biological methods used in biological phosphorus removal

Increasing attention has been paid to phosphate-accumulating organisms(PAOs)for their important role in biological phosphorus removal.In this study,microbial communities of PAOs cultivated under different carbon sources(sewage,glucose,and sodium acetate) were investigated and compared through culture-dependent and culture-independent methods,respectively.The results obtained using denaturing gradient gel electrophoresis(DGGE)of polymerase chain reaction-amplified 16S rDNA fragments revealed that the diversity of bacteria in a sewage-fed reactor(1#)was much higher than in a glucose-fed one(2#)and a sodium acetate-fed one(3#);there were common PAOs in three reactors fed by different carbon sources.Five strains were separated from three systems by using a phosphate- rich medium;they were from common bacteria isolated and three isolates could not be found in DGGE profile at all.Two isolates had good phosphorus removal ability.When the microbial diversity was studied,the molecular biological method was better than the culture-dependent one.When phosphorus removal characteristics were investigated,culture-dependent approach was more effective. Thus a combination of two methods is necessary to have a comprehensive view of PAOs.     

典型街道环境空气质量分析

根据对深南东路环境空气的监测及车流量、气象条件的调查,分析机动车及气象因素对深圳市环境空气质量的影响。根据分析可知,机动车尾气是深圳市环境空气中污染物的主要来源,但污染程度不断变化的主要原因是风速,深圳市环境空气中污染物浓度与风速有着非常显著的负相关。     

环境监控(监测)建设与发展过程的思考

论述环境监控系统的发展过程、具体应用和建设的意义。叙述环境监控系统的建设为解决环境质量监测、污染源在线自动监测和生态监测与具体部门相关联而造成信息孤岛的问题,提倡环保多业务综合共享信息的标准化;环境监控系统的建设是基础,应用是关键,运行维护管理是保障,三者不可偏废。让环境管理者产生形象思维,拓宽思路和视野,发现和解决新问题。     

基于DEMATEL/ISM的地下商业街火灾风险影响因素研究

为研究某地下商业街火灾风险影响因素，针对该地下商业街火灾的复杂性和特殊性，建立了包括人员、设备、环境、管理等4个大类下的16个影响因素的火灾风险影响因素指标体系，运用DEMATEL方法分析影响火灾风险的关键因素，并结合ISM方法建立影响因素多层次递阶解释结构模型。结果表明：火灾风险由多种影响因素耦合而成，消防人员工作能力、地下建筑结构复杂度、消防资金投入大小和消防安全规程的执行力度是影响地下商业街火灾的关键因素。     

古商业街木结构建筑防火间距的数值模拟研究

古商业街木结构建筑较多,防火间距先天不足,发生火灾后蔓延迅速,有必要开展木结构建筑引燃特性研究以获得合理的防火间距设置参数.以古商业街为研究对象,以临界温度和热辐射强度作为着火建筑对面木结构建筑被引燃的判定指标,综合考虑环境风速、建筑间距、火源功率、喷淋系统等因素,运用火灾动力学模拟软件FDS分析系列火灾场景下的温度和...