Atmospheric Environment. Part B. Urban Atmosphere最新文献

Environmental tobacco smoke, mosquito-coil smoke, and joss stick smoke are the major indoor combustion sources in Asian countries. Field evaluations of the size distributions of outdoor submicron particles and selected combustion sources of indoor particles were conducted in an apartment in Taipei urban area. The size distributions of submicron aerosols were determined by a high resolution particle sizer, which could measure the particles in the size range of 0.017–0.886 μm. The particle sizer contains a differential mobility analyser (TSI 3071) and a condensation particle counter (TSI 3022). The number concentrations of the indoor and outdoor submicron particles varied from 14,000 to 150,000 cm⁻³ and from 10,000 to 45,000 cm⁻³, respectively. The changes of the size distributions and the number concentrations of submicron aerosols before, during, and after the aerosol generations were compared. The average number median diameters of environmental tobacco smoke, smoldering cigarettes, mosquito-coil smoke, joss stick smoke, the indoor typical conditions, and the outdoor typical conditions were 0.090, 0.085, 0.094, 0.084, 0.091 and 0.054 μm, respectively. Regarding the surface area-weighted size distributions, the average surface median diameters of these conditions were 0.229, 0.219, 0.282, 0.188, 0.224 and 0.221 μm, respectively. In addition, the average volume median diameters were 0.338, 0.332, 0.398, 0.289, 0.330 and 0.340 μm, respectively. These indoor combustion sources did generate a significant number of the ultrafine and submicron particles which have higher deposition probabilities in the respiratory tract. Further health evaluations of the submicron particles from these combustion sources are needed.

The CAR model (Calculation of Air pollution from Road traffic) is a simple parameterized model for the determination of air quality alongside roads (including street canyons) in cities. The calibration of the model, using data from the Dutch National Air Quality Monitoring Network, is described and a limited validation of the model is given. The model supports the implementation of air quality decrees under the Air Pollution Act by provincial and municipal authorities. Various applications of the model, including a scenario analysis for city street air quality in the Netherlands in the period 1989–2010, are presented.

During the last two decades, the urban areas in the city of Riyadh—the capital of Saudi Arabia—were increasing at an exceptionally high rate through a series of development plans. The major plans had been completed by the end of 1982. Some other big utility projects were started and completed during 1987. As a consequence, the air quality has deteriorated markedly and air pollution episodes recorded during these activities showed that particulates were present in the atmosphere at high concentrations. Later in January 1991 the Gulf war started and the firing of the oil fields in Kuwait soon followed. It was estimated that soot particulates were emitted at a rate of 600 ton d⁻¹ along with high rates of other gases. This event has led to significant air quality and visibility problems.

Direct normal solar radiation has been measured during the summer months of July and August which were characterized by very dry and cloudless weather for the period between 1982 and 1992. A year-to-year trend of the transmittance of direct normal solar irradiance was then determined.

The atmospheric fine aerosol (<2 μm diameter) loading data during the same period were used to establish a correlation between the aerosol concentration and the extinction coefficient.

The total horizontal and direct normal solar radiation measurements during some days when the dark smoke emitted from the oil field fires in Kuwait were passing over Riyadh are presented. The reduction in solar irradiation reflects the intensity of dark smoke at a distance of 500 km from Kuwait.

A model is developed for the spatial and temporal evaluation of traffic emissions in metropolitan areas based on sparse measurements. All traffic data available are fully employed and the pollutant emissions are determined with the highest precision possible. The main roads are regarded as line sources of constant traffic parameters in the time interval considered. The method is flexible and allows for the estimation of distributed small traffic sources (non-line/area sources). The emissions from the latter are assumed to be proportional to the local population density as well as to the traffic density leading to local main arteries. The contribution of moving vehicles to air pollution in the Greater Athens Area for the period 1986–1988 is analyzed using the proposed model. Emissions and other related parameters are evaluated. Emissions from area sources were found to have a noticeable share of the overall air pollution.

The causes of the poor air quality in Athens, Greece during the severe episode of 25–26 May 1990 has been studied, using a prognostic model (RAMS) and a three-dimensional Eulerian air quality model (CALGRID). The modeling effort indicates that the main urban area of Athens exhibited high concentrations of nitrogen oxides, the main sources of which are automobiles, while the NNE suburban area exhibited high ozone concentrations, the product of photochemical activity of the primary pollutants that were transported by the sea-breeze. The application of the models also demonstrated the need for an accurate emission inventory for improved predictions of the pollutant concentrations. It was also found that a 50% reduction of the nitrogen oxide emissions will increase the ozone levels in the downtown area substantially.

The photochemical box model (PBM) developed in the present study is based on the principle of mass conservation. It has a horizontal domain of the size of a typical city and a vertical dimension defined by the mixed-layer height. The concentration of any pollutant is determined by horizontal advection, vertical entrainment, source emissions and chemical reactions. A one-dimensional high resolution boundary layer model by Blackadar (Preprints, Third Symp. on Atmospheric Turbulence, Diffusion, and Air Quality, Raleigh, Am. Met. Soc., pp. 443–447, 1976; Advances in Environmental Sciences and Engineering, Vol. 1, No. 1 (edited by Pfafflin J. and Ziegler E.), pp. 50–85. Gordon and Breach, New York, 1979) has been incorporated in the PBM and further developed to consider the effect of urban heat islands in the simulation of mixed layer height. The predicted mixed-layer heights compare very well with observations. The gas phase chemical kinetic mechanism used in the Regional Acid Deposition Model II (RADM2) and that of an earlier version of PBM have been used to calculate the contributions of chemical reactions to the changes of pollutant concentrations. Detailed analysis and comparisons of the two chemical mechanisms have been made. The simulated pollutant concentrations using both chemical mechanisms are in very good agreement with available observations for CO, NO, NO₂ and O₃. A radiative transfer model developed by Madronich (J. geophys. Res.92, 9740–9752, 1987) has been incorporated in the PBM for the calculation of actinic flux and photolytic rate constants. Height-averaged and radiation-corrected photolytic rate constants are used for the photochemical reactions. Budget analyses conducted for CO, NO, NO₂ and O₃ have enhanced our understanding of the relative contributions of horizontal advection, vertical entrainment, source emissions and chemical reactions to the overall rate of change of their concentrations. Model predictions are not sensitive to the large number of peroxy radical-peroxy radical reactions in the RADM2 chemical mechanism under urban conditions.

A method has been developed that explicitly accounts for the effect of meteorological fluctuations on the annual distribution of ground-level ozone in urban areas. The model includes a trend component that adjusts the annual rate of change in ozone for concurrent impacts of meteorological conditions, including surface temperature and wind speed. The model was applied using available data from 43 urban areas throughout the U.S.A. where ozone levels frequently exceed the National Ambient Air Quality Standard. The results suggest that meteorologically adjusted upper percentiles of the distribution of daily maximum 1-h ozone are decreasing in most urban areas over the period from 1981 to 1991. The median rate of change was −1.1% per year indicating that ozone levels have decreased approximately 11% over this time period. Trends estimated by ignoring the meteorological component appear to underestimate the rate of improvement in ozone primarily because of the uneven year-to-year distribution of meteorological conditions favorable to ozone.