Atmospheric Environment. Part B. Urban Atmosphere最新文献

One of the goals of NAPAP-sponsored research on the effects of acidic deposition on carbonate stone has been to quantify the incremental effects of wet and dry deposition of hydrogen ion, sulfur dioxide and nitrogen oxides on stone erosion. Test briquettes and slabs of freshly quarried Indiana limestone and Vermont marble have been exposed to ambient environmental conditions in a long-term exposure program. Physical measurements of the recession of test stones exposed to ambient conditions at an angle of 30° to horizontal at the five NAPAP materials exposure sites range from ∼ 15 to ∼ 30 μm yr⁻¹ for marble, and from ∼ 25 to ∼ 45 μm yr⁻¹ for limestone, and are approximately double the recession estimates based on the observed calcium content of run-off solutions from test slabs. The difference between the physical and chemical recession measurements is attributed to the loss of mineral grains from the stone surfaces that are not measured in the run-off experiments. The erosion due to grain loss does not appear to be influenced by rainfall acidity, however, preliminary evidence suggests that grain loss may be influenced by dry deposition of sulfur dioxide between rainfall events. Chemical analyses of the run-off solutions and associated rainfall blanks suggest that ∼ 30% of erosion by dissolution can be attributed to the wet deposition of hydrogen ion and the dry deposition of sulfur dioxide and nitric acid between rain events. The remaining ∼ 70% of erosion by dissolution is accounted for by the solubility of carbonate stone in rain that is in equilibrium with atmospheric carbon dioxide (“clean rain”). These results are for marble and limestone slabs exposed at an angle of 30° from horizontal. The relative contribution of sulfur dioxide to chemical erosion is significantly enhanced for stone slabs having an inclination of 60° or 85°. The dry deposition of alkaline particulate material has a mitigating effect at the two urban field exposure sites at Washington, DC, and Steubenville, OH.

The Thriassion plain is a heavily industrialized area to the west of the Athens basin, separated from it by Mount Aegaleo, a 468-m high ridge about 15 km long. Three field experiments were performed to determine the possibility of air pollutant transport into the Athens basin. Sulphur hexafluoride (SF₆) was released from one of the stacks of the Hellenic Oil Refineries, situated in the eastern part of the Thriassion plain, together with several releases of tetroons. These experiments revealed two mechanisms of air mass transport from the Thriassion plain, a daytime mechanism, when the air mass is transported along the Mount Aegaleo ridge and through the passage between Mount Aegaleo and Mount Parnitha to the north, and a nighttime mechanism, when transport occurs over Mount Aegaleo. SF₆ was released only during the night and although in all three occassions it reached the western suburbs of Athens, it did so by different simultaneous mechanisms. Furthermore its advection-diffusion once in the basin showed large variability, whose cause was the details of the flow field as it developed under the influence of the thermal stratification. The experiments demonstrate the complexity of the diffusion of air pollutants in complex terrain and the influence of both the details of the flow field and the stratification in determining the local ground-level concentrations. They also point out the need for simultaneous modelling of both factors, for the correct computation of pollution levels.

This paper examines the relationship between various types of particulate data collected in Brisbane, Queensland, Australia—PM10, TSP, lead and nephelometer data. Statistical tests on the data show: the PM10 data collected at all sites throughout the city are closely correlated, the same for lead but not TSP data; PM10 and TSP data collected at the same site are closely correlated, and both are only weakly correlated with nephelometer data; the lead data sets at the same site are significantly correlated with the TSP, PM10 and nephelometer data; and windspeed data generally show significant negative correlation only with the lead data. The results indicate that PM10 data would appear to be approximately a constant proportion of the TSP data throughout the year, and there is no evidence to suggest that anthropogenic emissions only contribute to the PM10 fraction or that ‘natural’ sources contribute only to the coarser fraction of the TSP data. However the lead data and the nephelometer data arise from a distinctly different pattern of sources to the TSP and PM10 data, and events, with motor vehicle emissions being clearly important in the area studied (comprising more than 95% of all lead emissions).

The objective of this paper was the study of relationships between solar radiation trends and pollution situations recorded in the downtown area of a large industrial city in southern Europe (Turin, Italy). Two pollution indices (one of them based only on gas and particulate pollution load and the other one including the meteorological parameters which are most relevant to atmospheric dispersion) have been defined in order to attempt to quantify the phenomenon. Good correlations between the above indices and solar radiation levels have been observed. An estimation of the atmospheric turbidity in the urban area has then been assessed with different methods, in order to set up an empirical approach to the description of connections existing among solar radiation data, air pollution and atmospheric conditions.