Atmospheric Environment. Part B. Urban Atmosphere最新文献

A synoptic climatology demonstrates the relationships between the atmospheric circulation and surface ozone (O₃) concentrations. To deduce these associations, a subjective synoptic classification scheme is applied to 10 years' O₃ data from the Pittsburgh metropolitan area. The results focus on four aspects of the atmospheric circulation-O₃ relationship: average, extreme-event, between season and year-to year conditions. On average, each of the nine circulation types is related to a characteristic O₃ concentration level and cumulative O₃ dose. Extreme high-O₃ events are associated with either the western side of a slowly migrating anticyclone or a stagnating extended high-pressure ridge; low-O₃ events are experienced under cool and cloudy cyclonic conditions. Between-season variations in the average and extreme circulation-O₃ relationshipsare observed: the high-pressure features that produce the high st O₃ levels in summer are related to low levels in winter, while circulation patterns that contribute very little to summertime O₃ build-up are associated with the highest levels of wintertime O₃. The latter situation could be caused by tropopause folding and the introduction of stratospheric ozone in winter months. While zonal (meridional) circulation regimes tend to produce lower (higher) mean annual O₃ levels, such year-to-year changes in synoptic-type frequencies do not appear to be strongly related to interannual variations in O₃, and other non-climatic factors appear to be of greater importance.

In the future most of the world's population will live in urban areas and there also most economic activities will be concentrated. This will lead to enormous environmental and climatological problems, unless urban planners and architects develop a new urban planning strategy and building design methods, which will enable the continuation of the growth of urban areas and also enable its population to live and work in a good climatic environment. To achieve this goal this article presents a new comprehensive climatological and environmental urban planning concept. This concept includes the new term of “climate quality”, which is no less important in the urban space than is air quality. The combination of using alternative energy sources together with integrating climatological factors in all urban planning levels will lead to an expected improved climatic and environmental quality of the urban area.

Particulate pollutants in air samples from different parts of the city of Riyadh, Saudi Arabia, were studied prior to the Gulf war, employing energy dispersive X-ray fluorescence technique. Eight significant elements were found. Particular attention was paid to the study of the pollutants Fe, Ni, Cu, Zn and Pb due to their potential toxicity. These results will be of interest given the changed conditions.

A stochastic approach to the problem of incorporating variable emission events in indoor air quality models is proposed. A nonstationary Poisson process is used to account for the occurrence of range-top burner use. The combination of this emission event sequence with a simple one-compartment mass-balance model results in output that qualitatively agrees with measured concentrations in two occupied townhouses. Improved monitoring of stove usage times, gas flow rates and emission factors under field conditions would allow more effective estimation of model input parameters and more accurate prediction of concentration distributions.

The large-scale planting of shade trees in urban areas to counteract heat-island effects and to minimize energy use is currently being discussed. Among the costs to be considered in a cost/benefit analysis of such a program is the potential for additional reactive organic compounds in the atmosphere due to emissions from these trees. In this program, 15 species of potential shade trees for the Los Angeles Air Basin were studied and emission rates were determined for 11 of these trees, with one further tree (Crape myrtle) exhibiting no detectable emissions. The emission rates normalized to dry leaf weight and corrected to 30°C were (in μg g⁻¹ h⁻¹), ranked from lowest to highest emission rate: Crape myrtle, none detected; Camphor, 0.03; Aleppo pine, 0.15; Deodar cedar, 0.29; Italian Stone pine, 0.42; Monterey pine, 0.90; Brazilian pepper, 1.3; Canary Island pine, 1.7; Ginkgo, 3.0; California pepper, 3.7; Liquidambar, 37; Carrotwood, 49. In addition to the emission rates per unit biomass, the biomass per tree must be factored into any assessment of the relative merits of the various trees, since some trees have higher biomass constants than others. The present data shows that there are large differences in emission rates among different tree species and this should be factored into decision-making as to which shade trees to plant. Based solely on the presently determined emission rates, the Crape myrtle and Camphor tree are good choices for large-scale planting, while the Carrotwood tree and Liquidambar are poor choices due to their high isoprene emission rates.

A regional air pollution model, based on the solution of the Langevin equation, is developed and validated for both point and area sources. By incorporating the spatial and temporal variations in motor vehicle emissions for Perth, Western Australia, the model is able to reproduce the observed magnitude and spread of the urban plume.

A three-dimensional numerical mesoscale air quality model is applied to study the effect of pollutant recirculation in the eastern Mediterranean, southern coastal plain of Israel. The model is based on the integration of two submodels: a mesoscale submodel and a Lagrangian dispersion submodel. The model is validated using air quality data measured during a severe pollution event in the city of Ashdod. When the recirculated portion of the pollution was separated from that directly contributed by the sources, it was found to constitute about 50% of the total concentration measured.

A stepwise cluster analysis method has been advanced and applied to air quality prediction. The method has improved monovariate A.I.D. (Automatic Interaction Detection) Algorithm, and can effectively deal with continuous and discrete variables, as well as nonlinear relations between the variables. In the application to air quality prediction, all source variables can carry information about air quality variations, and clustering results are given by cluster trees, so that a set of forecasting systems, which is flexible to reflect changes in source value distributions, can be formed.

In a case study, the method was applied to air quality prediction in the urban district of Xiamen, China. Data concerning three pollutant concentrations and four source types from 31 grid squares during 1984–1988 were used in the calculation. The results of cluster analysis were applied to the prediction of air quality in 1989. Through graphical and statistical tests, it was indicated that 82.8% of monitored concentrations were within the predicted radius, and, compared with the predicted mean concentrations, 76.3% of the predicted data had relative errors lower than ±20%, and 61.3% had errors lower than ±15%; thus showing the good performance of the method.

Wet precipitation was collected in Thessaloniki, Greece, during the period March 1989–December 1990 by using an automatic wet-only precipitation sampler.

Rainwater samples were analysed for major cations (H⁺, NH₄⁺, Na⁺, K⁺, Ca²⁺, Mg²⁺) and anions (Cl⁻, NO₃⁻, SO₄²⁻), in addition to acidity and conductivity measurements. The majority of rain had a neutral or alkaline character as a result of neutralization, primarily caused by calcareous soil dust and secondarily by atmospheric ammonia. In all rain, SO₄²⁻ concentration exceeded NO₃⁻ concentration. The contribution of maritime sources to the total SO₄²⁻ concentration was very low (<2%).

The chemical composition of precipitation was analysed in conjunction with meteorological variables (season of the year, precipitation type, airflow patterns) to evaluate temporal variations and chemical source influence. Rain caused by weak, localized flows showed the highest acidity and the minimum influence of neutralization processes.

A description of the California Line Source Dispersion Model, CALINE, is given along with a brief history of its development. The model is based on the Gaussian plume methodology and is used to predict air pollutant concentrations near roadways. Predictions can be made for carbon monoxide, nitrogen dioxide and suspended particulates.

There are two versions of the CALINE model in current use. CALINE3, published in 1979, replaced the virtual point approximation contained in earlier versions of the model with an equivalent finite line source representation and added a multiple link option. CALINE4, published in 1984, incorporated flexible input/output options including an option for modeling air quality near intersections. It also includes dispersion algorithms to account for vehicle-induced thermal turbulence and wind direction variability.

CALINE4 is verified using results from five separate field studies. Comparisons to CALINE3 indicate modest improvements in the accuracy of the newer version.