Traffic control oriented impact on the persistence of urban air pollutants: A causeway bay revelation during emergency period

The continuous traffic flow is always considered to take a great extent responsibility for the air quality deterioration in urban areas. Meanwhile, traffic control is assumed to be one of the most effective ways to mitigate the high concentration situation as this may cut off the emission directly and satisfy the air quality objectives. Unfortunately, the overdevelopment of central business district area in megacities not only complicates the control plan, but also troubles the process of plan assessment. Because of the road blockages caused by the radical behavior during the Hong Kong protest in 2014, it offers an unexpected chance to evaluate the influence of traffic control oriented plan on urban (i.e., Causeway Bay) air pollution. Hence, we here investigated the six air pollutants concentrations that measured in the time series before, during and after the Hong Kong Protest period. The impact of traffic flow restriction on pollutants’ persistence has been quantified both qualitatively and quantitatively in this study. The results showed that the persistence of pollutants was a general property in Causeway Bay which dominated by the traffic flow pattern. The road blockages, considered as one kind of extreme traffic control plan, would strengthen the persistence of most pollutants (except ozone). Moreover, it also indicated that comprehensive consideration and further balance among different pollutants were necessary when try to reduce pollution in urban area by traffic control.     

城市轨道交通在北京市城市结构调整中的作用及对策

从分析北京市现有的城市规划布局和交通中存在的问题出发,总结伦敦等大城市施行“有机疏散“规划的经验,探讨城市轨道交通在北京城市结构调整中的作用,并提出相关的对策。     

Microbial community structure in the marginal ice zone of the Bellingshausen Sea

Phytoplankton, bacteria and microzooplankton were investigated on a transect in the Bellingshausen Sea during the ice melt period in November–December 1992. The transect along the 85°W meridian comprised seven stations that progressed from solid pack-ice (70°S), through melting ice into open water (67°S). The abundance, biomass and taxonomic composition were determined for each component of the microbial community. The phytoplankton was mostly dominated by diatoms, particularly small (<20 μm) species. Diatom abundance ranged from 66 000 cells l⁻¹ under the ice to 410 000 cells l⁻¹ in open water. Phytoplankton biomass varied from <1 to 167 mg C m⁻³, with diatoms comprising 89–95% of the total biomass in open water and autotrophic nanoflagellates comprising 57% under the ice. The standing stocks of autotrophs in the mixed layer ranged from 95 mg C m⁻² under the pack-ice to 9478 mg C m⁻² in open waters. Bacterial abundance in ice-covered and open water stations varied from 1.1 to 5.5×10⁸ cells l⁻¹. Bacterial biomass ranged from 2.4 mg C m⁻³ under pack-ice to an average of 14 mg C m⁻³ in open water. The microzooplankton consisted mainly of aloricate oligotrich ciliates and heterotrophic dinoflagellates and these were most abundant in open waters. Their biomass varied between 0.2 and 54 mg C m⁻³ with a minimum at depth under the ice and maximum in open surface waters. Microheterotrophic standing stocks varied between 396 mg C m⁻² under pack-ice and 3677 mg C m⁻² in the open waters. The standing stocks of the total microbial community increased consistently from 491 mg C m⁻² at the ice station to 13 155 mg C m⁻² in open waters, reflecting the productive response of the community to ice-melt. The composition of the microbial community also shifted markedly from one dominated by heterotrophs (82% of microbial stocks) at the ice station to one dominated by autotrophs (73% of microbial stocks) in the open water. Our estimates suggest that the microbial community comprised >100% of the total particulate organic carbon (POC) under the ice and 62–66% of the measured POC in the open waters.     

有机锗多酸衍生物对S_(180)肿瘤细胞DNA合成的抑制作用

目的　探讨有机锗多酸衍生物对S1 80 肿瘤细胞DNA合成的抑制作用。方法　用3H TdR掺入法检测有机锗多酸衍生物在体外对S1 80 肿瘤细胞DNA合成的抑制作用 ,观察不同剂量有机锗多酸衍生物对S1 80 实体瘤的抑制作用和对免疫器官的影响。结果　体外实验表明 ,有机锗多酸衍生物对S1 80 细胞的生长具有明显的抑制作用 ,而且浓度越高 ,抑制作用越强。体内实验也表明 ,有机锗多酸衍生物对S1 80 实体瘤的生长具有抑制作用 ,而且剂量越大 ,抑制作用越强。且有机锗多酸衍生物可防止荷瘤鼠脾脏重量的下降。结论　有机锗多酸衍生物可抑制肿瘤细胞生长 ,并存在剂量依赖关系     

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在对微观(路段和交叉口)环境交通容量分析的基础上，运用机动车尾气扩散箱型模式建立路段环境交通容量计算模型。考虑满足环境空气质量标准和保证路段的通行能力，本文主要考虑降低机动车污染物排放因子，并得出了相应的计算模型。最后对北京某路段环境交通容量进行初步计算分析。该模型的提出可为城市规划、交通规划和交通管理决策提供参考。     

宁波市区道路汽车行驶工况调查研究

利用GPS调查了宁波市不同道路汽车行驶工况，记录了实际道路汽车行驶瞬时速度的大量数据．根据这些调查数据进行了不同道路汽车行驶工况的解析，分别建立起适合宁波市汽车排放污染物测量的一般道路汽车行驶工况、快速道路汽车行驶工况、城区综合道路汽车行驶工况的监测系统。     

新龙门隧道射流通风与污染物浓度的数值分析

提出了按具有运动污染源一维非恒定流模型计算隧道内气流速度和污染物浓度分布的方法，并对新龙门隧道进行了数值模拟，阐述了内燃机产生的有害气体的危害及组成成分，并按牵引功率计算出排污量；分析了影响污染浓度分布的各种因素。对列车在洞内交会地点、射流风机工作时间及风机的送风方向进行了综合比较，提出了有利工况。     

Influence of avenue trees on traffic pollutant dispersion in asymmetric street canyons: Numerical modeling with empirical analysis

The dispersion of traffic-related pollutants in urban street canyons is of importance for the health and quality of lives. To reveal the inherent principle, researchers have performed a lot of investigations; many dispersion phenomena have also been assessed during recent years. However, the presence of avenue trees in street canyons and their capacity for pollutant dispersion remains partly addressed. In this study, we investigated the effects of avenue trees in urban street canyons on traffic pollutant dispersion. The dispersion of CO concentration in asymmetric street canyons was simulated under varied situations. The computational results showed a good agreement with the experimental data, and the numerical model was validated to be adequate for investigating the pollutant dispersion in street canyons. Then, the numerical simulations were extended to explore the impacts of the effects of avenue trees on CO dispersion; the results indicated that avenue trees generally increase CO concentrations in asymmetric street canyons. When the wind direction is perpendicular to the street axis, a terraced building raises pollutant concentrations at the windward wall and reduces concentration at the leeward wall on the pedestrian levels. Findings of this study are expected to provide significant insight into urban road design and strategy making for avenue tree planting, particularly under the existing worldwide sustainable low-carbon urban development.     

高铁箱梁支座钢板空响的病害预防与补救研究

支座是铁路桥梁的重要组成部分，它支撑着桥梁和过往列车的全部重量，以及列车的动荷能量，它在起到支撑和固定梁体的同时，还要起到梁体在受外力变形和受温度变化而变形时的自由伸缩的调节作用，铁路桥梁在运营过程中，支座在列车荷载作用下，支座底面与桥墩支撑垫石均会受到巨大的动能冲击。着重讨论高铁箱梁支座钢板空响的痛害预防与补救措施，对高铁箱梁支座预埋钢板产生空响的原因与可能导致的危害进行逐一深入分析，研究预防与补救高铁箱梁支座钢板发生空响可行措施。     

A STUDY ON RELATIONSHIP BETWEEN ORGANIC SUBSTANCES IN WATER AND PREVALENCE OF KASHIN BECK DISEASE

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