Urban environment emissions

Carbon monoxide (CO) Is one of the most widely distributed air pollutants. It Is formed by natural biological and oxidation processes, the Incomplete combustion of carbon-containing fuels and various Industrial processes. However, the largest Individual source of man-made emissions Is motor vehicle exhausts which account for virtually all CO emitted In some urban environments. It has been estimated that global man-made emissions range from 300-1600 million tons per year, which Is approximately 60% of the total global CO emissions (22-23). 

In 1982-1983, the baseline value for daily intake of lead by inhalation in a nonurban environment was estimated to be 0.5 pg/day for a 2-year-old child. The baseline value was based on an average atmospheric lead concentration of 0.1 pg/m3 and an indoor/outdoor lead concentration ratio of 0.5. In an urban environment, the indoor/outdoor ratio was assumed to be approximately 0.8 (EPA 1986a). Drastic reductions in the lead content of gasoline since 1986 have resulted in a 64% decrease in lead emissions to the atmosphere (see Section 5.4.1). 

Kousoulidou M, Ntziachristos L, Mellios G, Samaras Z (2008) Road-transport emission projections to 2020 in European urban environments. Atmos Environ 42 7465-7475... 

The complexity of the urban environment does not always allow for a clear separation of road traffic sources consequently, most of source apportionment studies present results only for total contributions from road traffic. It is also common to find studies where the road dust component of traffic emissions is mixed with other mineral/soil sources. Nevertheless, for air quality management and exposure studies it is important to understand the individual source contributions. PM contributions from vehicular traffic should be differentiated between exhaust and non-exhaust. Ideally non-exhaust contributions should be further separated between road dust, brake, tyre and road wear. 

Hot-spot monitoring Publicly accessible areas in urban environments where highest concentrations of a pollutant are to be expected, including areas influenced by traffic or industrial emissions,... 

Waste incinerators have been identified as one of the major sources in the urban environment, and others include uncontrolled combustion. Car-exhaust emissions, especially from cars using leaded gasoline with halogenated scavengers also contain considerable levels of PCDD/Fs. 

S. Rauch, G. M. Morrison, Routes for bioaccumulation and transformation of platinum in the urban environment, in F. Alt, F. Zereini (eds), Anthropogenic Platinum-group Metals Emission and Their Effect on Man and Environment, Springer, Berlin, 2000, pp. 85D93. 

The multimedia urban model (MUM) is a fugacity-based mass balance model that treats the movement of POPs in an urban environment and links emissions to ambient chemical concentrations, and thus outdoor exposure (Diamond et al., 2001). MUM considers longterm, average conditions of chemical transport and transformation among six environmental compartments in urban areas (air, soil, surface water, sediment, vegetation and surface film see Figure 6.1) shows a concepmal version of the model). The model does not estimate event-specihc processes as do meteorological-based air or stormwater models. 

Transportation is one of the most important sources of air pollution, particularly in urban environments. The total number of cars, trucks, buses and motorcycles in the world in 1990 was estimated at about 650 million [41] All these cars produce exhaust emissions. 

The role of the outdoor air on the indoor particle characteristics cannot be overestimated. In the absence of active indoor sources particles generated by outdoor sources which penetrated indoors are the main constituent of indoor particles. In a typical outdoor urban environment, motor vehicle emissions constitute the most important source of all pollutants including particles. The emissions from motor vehicles penetrate indoors and their concentration in indoor air is often comparable to the concentration outdoors. 

Indoor combustion sources are related mainly to cooking, heating and tobacco smoking. In addition, outdoor combustion products, which in urban environments originate most commonly from vehicle emissions, penetrate inside and contribute to indoor pollution. Under ideal conditions, complete combustion of carbon results only in the generation of CO2 and water vapour. Any products other than CO2 are often called products of incomplete combustion and include particulate matter and gases. 

The serious pollution episodes in the urban environment are not generally earned by the sudden increase in the emission of pollutants, but are rather a result of short-term unfavourable meteorological conditions. A cost-effective way to prevent the occurrence of high air pollution episodes might be the temporal reduction in emissions that is based on the meteorological and air pollution forecast. 

Monaci et al. (1997) performed a lichen-biomonitoring study in Siena by means of two different methods. The pattern of air quality in the study area was examined on the basis of the in situ frequency of different species of epiphytic lichens, i.e. using their species-specific sensitivity to the complex mixture of phytotoxic pollutants in the urban environment. The distribution of trace elements was evaluated quantitatively by an analysis of thalli of a tolerant species, P. caperata, known to be a reliable bioaccumulator of persistent atmospheric pollutants. The values obtained for Al, Ba, Cr, Cu, Fe, Pb and S were significantly higher in Sienese lichens over and above controls. Traffic was found to be the major source of atmospheric pollution. The pattern of trace-elemental deposition did not always coincide with air quality. lAP values were found to reflect essentially the emission of gaseous phytotoxic pollutants in the urban environment. 

Nitric oxide (NO) Nitric oxide is a colorless gas at room temperature and is slightly soluble in water. It is produced as a result of industrial emissions. In urban environment, automobile emissions can be a source of nitric oxide. In acid soils, nitrate can be reduced to nitric oxide. 

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