北京市地面街尘与径流中重金属的污染特征（Characteristics of Heavy Metals in Street Dusts and Urban Runoff in Beijing）

街尘作为城市各种污染物的载体和地表径流污染物的主要来源对水环境的影响日益受到关注.论文分析了北京市城区街尘与地表径流中重金属浓度和颗粒的粒径分布.结果表明:不同城市土地利用类型对街尘和径流中的重金属含量、颗粒粒径分布具有重要影响.在商业区、主要道路、住宅区、城中村4种土地利用类型中,街尘重金属浓度和地面单位面积重金属质量均以主要道路最高;径流重金属浓度由高到低顺序依次为:主要道路>城中村>居民区;主要道路和商业区街尘颗粒中细粒径占的比例较高,在全部土地利用类型的径流水样中颗粒物粒径分布差别不大;随着街尘中颗粒物粒径的减小,重金属浓度增加;街尘中小于149μm的颗粒物质量百分比和重金属浓度均较高,且在径流中这个粒径段的颗粒物含量也高,体积比达80%以上.建议在今后的城市街尘面源污染控制中应特别关注土地利用类型和街尘粒径的影响.     

The Modelling of Turbulence from Traffic in Urban Dispersion Models — Part I: Theoretical Considerations

The modelling of pollutant dispersion at the street scale in an urban environment requires the knowledge of turbulence generated by the traffic motion in streets. In this paper, a theoretical framework to estimate mechanical turbulence induced by traffic in street canyons at low wind speed conditions is established. The standard deviation of the velocity fluctuations is adopted as a measure of traffic-produced turbulence (TPT). Based on the balance between turbulent kinetic energy production and dissipation, three different parameterisations for TPT suitable for different traffic flow conditions are derived and discussed. These formulae rely on the calculations of constants that need to be estimated on the basis of experimental data. One such estimate has been made with the help of a wind tunnel data set corresponding to intermediate traffic densities, which is the most common regime, with interacting vehicle wakes.     

干旱区的城市生境特征与绿洲化对策

干旱地区的城市亦被称为绿洲。从其发生与生境状况分析,注意到近期城市的扩展已脱离绿洲型的发展轨道,而与全球城市模式类同,亦具城市化的共有弊病。又因所处区位受到荒漠气候的强烈影响,较其它地带的城市,其生境更加恶劣。干旱区居民长期凭借绿洲生境而生息劳动,早期出现的城市亦脱胎于绿洲。目前仍沿用绿洲以称城市,但与绿洲的生境相比较已面目全非,实质是以现代设施在荒漠中建立的水泥荒漠。目前全球范围正展开以改善城市生境为目标的生态城市建设,位处干旱区的城市应从其所在区位出发,以绿洲化作为生态城市建设目标,切实改善居民生存环境质量。应仿照绿洲,在外围营造阻隔荒漠气候侵袭的防护林,在市区通过营造片林与行道树,形成类似条田林网格局,以一定植被规模重构绿洲化城市,形成绿洲生境以改善城市居民生存条件,回归干旱区居民世世代代依存的绿洲空间。     

城市街道空气质量与道路绿化型式的关系

通过对街区中茂密行道树对空气污染物扩散的利弊进行理论分析的基础上，以CO为自然示踪气体，对西安市几个典型街道中的气态污染物浓度分布做了实测。实测结果指出，道路车流量的大小是行道树树冠的净化功能和对污染物扩散的阻碍作用所占权重的主要影响因素，行道树对污染物扩散的阻碍作用主要受控于树木郁闭度而非绿量，指出城市道路绿化不应盲目追求绿量的提高，并据此提出在街道绿化中应根据车流量的大小采取不同绿化方案的建议。     

郑州市城市土壤理化性质

在郑州市市区范围内采集53个0-20 cm土壤样品,研究了土样部分基本性状。结果表明,郑州市城市土壤有机碳含量为1.33-20.5 g/kg,平均值为8.01 g/kg;碱解氮含量为8.30-142 mg/kg,平均值为46.4 mg/kg;Olsen-P含量为2.40-70.4 mg/kg,平均值为21.8 mg/kg;pH值为7.70-8.95,平均值为8.36;城市化造成的土壤质地较粗对土壤有效性氮、磷提高和有机碳含量降低有一定贡献;土壤pH增加导致土壤有效磷含量降低;不同土地利用方式下土壤性质的对比表明,荒地质地粗、养分含量低、pH高;公园绿地和街边绿地土壤有效磷含量较高,街边绿地土壤有机碳含量较低。根据以上结果,减少土壤中粗骨性侵入体的含量和合理管理土壤磷对于郑州市城市土壤管理有现实意义。     

不同结构形状的街道峡谷内污染物扩散

针对不同的城市街道峡谷结构形状,通过求解二维不可压缩N-S方程和K-ε湍流模型方程及污染物对流扩散方程,数值模拟了街道峡谷内的流场及机动车排放污染物浓度场,从而说明了街道峡谷的结构是影响街道峡谷内污染气体扩散的主要因素之一。     

城市雨水口垃圾污染调查与研究

雨水口既是城市排水管系汇集雨水径流的瓶颈，又是城市非点源污染物进入水环境的首要通道，一旦被垃圾充塞，不仅导致排水不畅甚至水涝，还会对城市水体造成严重的污染。从对北京城区雨水口垃圾的抽样调查分析，和对雨水口垃圾产生的污染模拟实验和量化计算，讨论了我国城市雨水口垃圾问题的严重性和实施有效控制的重要性。     

广州市城市林业管理信息系统的研制开发

将ＧＩＳ技术引进技术林业研究，建立广州市城市林业管理信息系统，该系统具有采集，管理，分析和更新多种区域空间信息的能力，其分六个子系统，公园管理子系统，绿地管理子系统、市郊森林管理子系统、管理机构管理子系统，法规文件管理子系统。可以文字，数据，报表，图形，录像和声音等方式输入、存储、显示、输出绿化系统各类信息，并能随时查阅，检索、修改、录入、删除各类信息。     

Large-eddy simulation of turbulent flow and dispersion over a complex urban street canyon

Turbulent flow and dispersion characteristics over a complex urban street canyon are investigated by large-eddy simulation using a modified version of the Fire Dynamics Simulator. Two kinds of subgrid scale (SGS) models, the constant coefficient Smagorinsky model and the Vreman model, are assessed. Turbulent statistics, particularly turbulent stresses and wake patterns, are compared between the two SGS models for three different wind directions. We found that while the role of the SGS model is small on average, the local or instantaneous contribution to total stress near the surface or edge of the buildings is not negligible. By yielding a smaller eddy viscosity near solid surfaces, the Vreman model appears to be more appropriate for the simulation of a flow in a complex urban street canyon. Depending on wind direction, wind fields, turbulence statistics, and dispersion patterns show very different characteristics. Particularly, tall buildings near the street canyon predominantly generate turbulence, leading to homogenization of the mean flow inside the street canyon. Furthermore, the release position of pollutants sensitively determines subsequent dispersion characteristics.     

Influence of industry on the geochemical urban environment of Mieres (Spain) and associated health risk

This study is concerned with the elemental composition of soils and street dust collected in an historical industrial city of approximately 27 000 inhabitants, where old Hg mining and metallurgical activities strongly affected the load of heavy metals in the urban environment. For the purpose of the study, representative samples of soils and street dust were collected at different locations in the whole urban area (3 km²). Elevated mean concentrations of As in soils and street dust (69 and 135 g g^–1, respectively), and Hg (3.07 and 4.24 g g^–1, respectively), compared to background levels and to those found in other cities, reflect the anomalous geochemical nature of these materials and the strong influence exerted by the old mining sites.     

Human health risk from Pb in urban street dust in northern UK cities

The presence of Pb in the environment can cause significant health problems. These issues are exasperated when the lead is in a more amenable form for potential ingestion. This study investigates the potential human health risk from Pb in urban street dusts. The lead levels in urban street dust in major city centres in northern UK have been compared to levels determined in 35 cities around the world. With a few exceptions, it was noted that the mean Pb levels in this study exceeded those found in other cities worldwide. Samples (n = 15) of urban street dust were collected across five city centres, and specifically in areas in which pedestrians are likely to concentrate, as well as near historical buildings. Typical total lead concentrations across all sampling sites ranged from 306 to 558 mg/kg. The human health risk was assessed using oral bioaccessibility testing of the urban street dust. The mean oral bioaccessibility data, irrespective of site and sample location, were in the range 43 ± 9 %. The total and bioaccessible concentrations of lead were compared to the estimated tolerable daily intake (TDI_oral) values based on unintentional soil/dust consumption. It is noted, in all cases, that the maximum estimated lead daily intake exceeded the TDI_oral. An alternative approach for assessing the daily intake is proposed based on the actual measured air quality in selected cities on the same day as the sampled urban dust.     

Upstream Turbulence Effect on Pollution Dispersion

Experiments have been carried out to investigate turbulence at and above roof-level in an urban environment, and to predict the behaviour of street pollution from experiments using dye dispersion, for different roughness conditions and bed geometries. The flow in the boundary layer above an idealised urban environment has been simulated in a laboratory water flume. Comparisons have been made for the same model street canyon with and without the presence of upstream roughness. In the tests reported here, model street canyons were aligned perpendicular to the flow direction, and velocity measurements made within and above the model street canyons using a laser Doppler velocimeter (LDV). Flow visualisation techniques have also been used to confirm the gross flow features from streak images. Turbulence generated from the upstream roughness has a significant effect on the turbulence production and dispersion behaviour of the dye simulating pollution in street canyons.     

对城市雨水地下回灌的分析

城市扩张带来雨水径量增大,排出时间缩短并由此产生一系列后果,对城区雨水回灌地区的效益进行了讨论,分析城区雨水径流水质污污状况及其影响因素,初期雨水径流污染严重,主要受到地面条件,屋面材料,气温,降雨量及降雨强度等影响,根据对雨水水质的研究结果,分析了雨水回灌地下的条件及必要的雨水处理措施,对雨水回灌技术作了简略的论述。     

城市大气总悬浮颗粒物与城市热岛

城市大气总悬浮颗粒物是造成全球大部分城市空气污染严重的原因之一,世界各国对之已进行过很多的研究。大量的研究显示,总悬浮颗粒物的污染非常严重,是影响城市空气质量的首要污染物。总悬浮颗粒物的源以人为来源为主,其汇则以湿沉降为主。总悬浮颗粒物对城市气候的影响主要通过2种方式:一种是通过散射或吸收太阳辐射直接影响气候;另一种是以云凝结核的形式改变云的光学特性和云的分布而间接影响气候。但是总悬浮颗粒物与城市热岛相互关系的研究目前还未受到应有的关注,总悬浮颗粒物与城市热岛的相互作用尚未有定论,总悬浮颗粒物既有促进城市热岛形成,也有促进城市冷岛形成的研究报道。文章认为可从如下3个方面探讨总悬浮颗粒物与城市热岛的相互关系:(1)总悬浮颗粒物在城市热岛中的贡献;(2)总悬浮颗粒物影响城市热岛的作用机理;(3)总悬浮颗粒物与城市植被和城市热岛的相互关系及植被对总悬浮颗粒物的净化、对城市热岛的缓解。研究总悬浮颗粒物与城市热岛的相互关系为制定科学合理的城市大气总悬浮颗粒物污染防治措施,有效缓解现代城市热岛难题提供理论依据。     

A building-based data capture and data mining technique for air quality assessment

Recently, a building-based air quality model system which can predict air quality in front of individual buildings along both sides of a road has been developed. Using the Macau Peninsula as a case study, this paper shows the advantages of building-based model system in data capture and data mining. Compared with the traditional grid-based model systems with input/output spatial resolutions of 1–2 km, the building-based approach can extract the street configuration and traffic data building by building and therefore, can capture the complex spatial variation of traffic emission, urban geometry, and air pollution. The non-homogeneous distribution of air pollution in the Macau Peninsula was modeled in a high-spatial resolution of 319 receptors·km^-2. The spatial relationship among air quality, traffic flow, and urban geometry in the historic urban area is investigated. The study shows that the building-based approach may open an innovative methodology in data mining of urban spatial data for environmental assessment. The results are particularly useful to urban planners when they need to consider the influences of urban form on street environment.     

On thermally forced flows in urban street canyons

During sunny days with periods of low synoptic wind, buoyancy forces can play a critical role on the air flow, and thus on the dispersion of pollutants in the built urban environments. Earlier studies provide evidence that when a surface inside an urban street canyon is at a higher temperature than that of local ambient air, buoyancy forces can modify the mechanically-induced circulation within the canyons (i.e., gaps between buildings). The aspect ratio of the urban canyon is a critical factor in the manifestation of the buoyancy parameter. In this paper, computational fluid dynamics simulations are performed on urban street canyons with six different aspect ratios, focusing on the special case where the leeward wall is at a greater temperature than local ambient air. A non-dimensional measure of the influence of buoyancy is used to predict demarcations between the flow regimes. Simulations are performed under a range of buoyancy conditions, including beyond those of previous studies. Observations from a field experiment and a wind tunnel experiment are used to validate the results.     

城市街道汽车污染的多元回归分析

本文以沈阳市为对象，详细论述了城市街道分类、监测点位布置、汽车污染系统调查及污染规律分析。根据现有实测数据，重点进行了汽车污染的多元回归分析，并提出了城市街道汽车污染的防治途径。     

Urban expansion of oasis cities between 1990 and 2007 in Xinjiang,China

An oasis is not only the most concentrated area of human activity in an arid area but also the largest area where artificial disturbances occur at a regional scale. The study of oasis urban expansion and related factors is important to understand the development of cities in arid areas, guide the evolution of rational urban expansion and promote sustainable development of oasis cities. Although there have been several studies on urban expansion in Xinjiang over past decades, a lack of quantitative data and methods impedes further research. In this paper, urban expansion of the studied area in 1990, 2000 and 2007 is evaluated using 39 Landsat satellite images, a geographical information system (GIS) and remote sensing (RS). We also analyse the related factors of urban expansion using quantitative and qualitative methods. We found that economic development and the area of the urban administrative region greatly effect urban expansion. Too rapid growth and outward urbanized expansion paradigms should not be applied blindly in arid areas from the point of view of sustainability. Historic–geographic features of oases and urban planning influence oasis urban morphology. Compact urban morphology is relatively better for protecting precious water and arable resources, and reducing ecology damage to the surrounding oasis. The relationship between urban expansion and population growth was not coordinate before 2000, and effectively only improved after that date. City growth should be moderated, with lower elastic coefficients, slower expansion and higher elasticity coefficients. Oasis cities in Xinjiang are expanding under the combined effects of urbanization, economic development, transportation, environment, resources, policy and planning.     

论制约21世纪城市园林绿化发展的因素

改革开放以来，我国城市园林绿化事业虽然取得了长足进展，但仍面临着人多地少、资金严重缺乏的窘境，本文分析了产业这些问题的症结，提出了相应的对策与建议。     

天津城市道路灰尘重金属污染特征

以天津城市道路灰尘重金属为研究对象,按照环线分布将天津市中心城区划分为内环以内、内环-中环、中环以外3个区域,总共设置93个采样点。对表层灰尘进行采样收集,预处理后测定样品的理化性质,采用原子吸收光谱仪测定道路灰尘中重金属Cd、Cr、Cu、Ni和Pb的含量,进而分析天津市道路灰尘重金属的含量水平,运用ArcGIS软件中的地统计分析方法内插得出其空间分布特征,通过Pearson相关分析和主成分分析判析重金属来源。研究结果表明：道路灰尘颗粒粒径表现为双峰,主峰对应粒径较小,且为非正态分布,大量小粒径颗粒的存在使重金属含量增高;市区和各环区有机质变异系数较大,道路灰尘中有机质的空间分布差异较大,因而人为因素影响广泛;市区道路灰尘中重金属 Cd、Cr、Cu、Ni 和 Pb的平均含量依次为0.99、121.41、100.62、43.35和61.48 mg·kg-1,分别为天津土壤环境背景值的11.00倍、1.44倍、3.49倍、1.30倍和2.93倍;Cd、Cr和Cu的空间分布差异较大,Ni和Pb的空间分布差异较小;Pearson相关分析表明Pb-有机质（P＜0.05）, Cu-Ni（P＜0.01）和Cr-Cu（P＜0.05）之间存在显著正相关关系,主成分分析人为因素的积累贡献率为33.050%,自然因素的积累贡献率为57.315%,因此得出重金属受人为因素影响较大,交通尾气排放和工业污染为天津道路灰尘重金属污染的重要来源,且以多因子复合影响为主。