Influence of Building Density and Roof Shape on the Wind and Dispersion Characteristics in an Urban Area: A Numerical Study

The Computational Fluid Dynamics code CFX-TASCflow is used for simulating the wind flow and pollutant concentration patterns in two-dimensional wind-tunnel models of an urban area. Several two-dimensional multiple street canyon configurations are studied corresponding to different areal densities and roof shapes. A line source of a tracer gas is placed at the bottom of one street canyon for modelling street-level traffic emissions. The flow fields resulting from the simulations correspond to the patterns observed in street canyons. In particular and in good agreement with observations, a dual vortex system is predicted for a deep flat-roof street canyon configuration, while an even more complex vortex system is evidenced in the case of slanted-roof square street canyons. In agreement with measurement data, high pollutant concentration levels are predicted either on the leeward or the windward side of the street canyon, depending on the geometrical details of the surrounding buildings.     

铁合金矿热电炉大气污染控制对策研究

根据重庆市某县锰矿资源、环境实际情况,在分析12500kVA铁合金矿热电炉生产硅锰合金所产生的大气污染物状况和特性的基础上,着重就大气污染防治的工艺技术路线和效果进行了深入的分析研究,提出了有效减轻环境空气污染影响的大气污染控制对策措施。     

辽宁中部城市群大气污染现状及发展趋势分析

根据1987年-2000年辽宁中部城市群(沈阳、鞍山、本溪、抚顺、辽阳)的主要大气污染物(TSP、SO2、NOx)的现状监测值,分析了辽宁中部城市群大气污染的现状及污染程度。分析结果表明：辽宁中部城市群的主要大气污染污染是TSP和SO2;冬季是辽宁中部城市群大气污染最重的季节,夏季大气污染最轻;辽宁中部城市群大气污染最重的城市是本溪,其次是鞍山、沈阳、抚顺、辽阳。     

Monthly Mean Afternoon Mixing-Layer Depths “Tuned” to the Eco-Climatic Regions of the Canadian Prairie Provinces

A simple diagnostic model was used to derive afternoon (0000 UTC) mixing-layer depths from gridded zero hour output from the Canadian Global Environmental Multiscale (GEM) numerical weather model interpolated to approximately 200 locations in the Prairie provinces of Canada. Knowledge of the spatial pattern of monthly mean afternoon mixing-layer depths was enhanced by associating the annual cycles of monthly means with eco-climatic regions - regions with fairly uniform terrain and soils, and where similar vegetation indicate that the area experiences, on average, similar synoptic-scale weather and produces similar surface fluxes of heat and moisture. When the mixing-layer depth is used to assess the dilution of airborne pollutants or to determine the specific humidity of the boundary layer, the eco-climatic region rather than proximity to the location-of-interest should be the primary factor in the selection of an appropriate radiosonde site.     

Model Assessment of Air-Pollution in Prague

Results of relatively simple gaussian dispersion model are presented. This model, developed in the beginning of this decade, is suitable mainly for determination of spatial distributions of annual mean concentrations of such kinds of air-pollution as sulphur dioxide (SO₂), mixture of nitrogen oxides (NO_x) or suspended particulate matter (SPM) from all types of emission sources located within the city - point sources, line sources and area sources. Model has been used in years 1994, 1996 and 1998 to assess the air-pollution distributions of the above mentioned kinds in the Prague area and the development of the air quality state. It contributed to the decision making process when possible impact of some changes in traffic system or in system of domestic heating, for example, has been investigated. In this contribution, behaviour of sulphur dioxide (SO₂) and mixture of nitrogen oxides (NO_x) ground concentration distributions are analyzed with respect to changing emission situation in Prague in recent years. Results show that SO₂ ground concentration level decreases mainly due to changes in local heating methods and type of fuel used. Different trend can be seen in NO_x ground concentrations thanks to rapid increase in the traffic density.     

不同大气污染区林木根区土壤重金属和酶活性研究

黄埔区是广州市污染较严重的地区,其中林木也受到了大气等污染物的危害。林木根区的土壤重金属和酶活性是探讨污染对林木影响机制和反映污染程度的重要指标。作者分别在该区的石化厂、硫酸厂附近林地和非污染的华南农业大学校园(对照)共3个区选择了台湾相思、马尾松、尾叶桉和荔枝4个树种、11个采样点,共采集了33个供试土壤样品,分析了林木根区土壤重金属(Cu、Zn、Pb、Cd)全量、有效量和土壤酶(脲酶、过氧化氢酶、酸性磷酸酶和蛋白酶)活性。结果表明,(1)石化厂重金属含量总体上与对照区差异不大,而硫酸厂区重金属含量则显著地高于对照区,污染严重。(2)不同调查区根区土壤酶活性存在显著差异,各调查区平均土壤酶活性大小顺序基本上表现为:对照区>石化厂区>硫酸厂区,尤其是硫酸厂区显著地低于对照区;而同一调查区不同树种之间的酶活性也存在差异,台湾相思根区土壤脲酶的活性均比其它树种高;从酶活性看,在硫酸厂严重污染胁迫下,台湾相思比尾叶桉更耐污染。(3)对土壤重金属含量和酶活性进行典型相关分析得出:根区土壤有效Zn含量对过氧化氢酶和酸性磷酸酶活性有明显的刺激作用,但抑制了蛋白酶活性;有效Cd则抑制了过氧化氢酶和酸性磷酸酶活性,但刺激了蛋白酶活性。     

湖北铝电解行业废气污染控制对策探讨

湖北铝电解企业的主要污染源是电解车间的电解槽.氟化物、沥青焦油和粉尘等为主要污染因子.目前采用了湿法、干法、分隔法和高空稀释排放等方法控制污染,难以做到达标排放.国家要求所有排污企业必须近期实现达标排放.进行技术改造已刻不容缓.并提出改自焙槽为预焙槽的两种方案,既有具有前瞻性的大型方案,也有具有现实性的小型方案.