Urban environment sources

FIGURE 7.4 Polymers mostly found in the urban environment (Source Aparecida s Adaption (2004)). 

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). 

As seen in Table 12-2, global NO production is dominated by anthropogenic sources. In an urban environment, virtually all NO is from fossil fuel combustion. 

Transportation is a major source 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. All these vehicles produce exhaust, and an esti-... 

Peculiarities in the daily cycle of N have been observed for the Mediterranean climate presenting peaks at midday which do not correlate with the levels of BC, indicating that a source other than traffic is influencing this parameter [65,74,75,97]. Similar results were found in Brisbane (Australia) and Los Angeles urban environments, with subtropical climates [98-100], Conversely, this phenomenon has not been observed for cities in central and northern Europe, where N levels vary proportionally to those of BC during the whole day [101, 102],... 

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. 

Mazzei F, D Alessandro A, Lucarelli F, Nava S, Prati P, Valli G, Vecchi R (2008) Characterization of particulate matter sources in an urban environment. Sci Total Environ 401 81-89... 

Morawska and co-workers have produced a number of review articles on this topic. For example, Holmes and Morawska [20] reviewed several simple and complex models covering a wide range of urban scales for the dispersion of particulate matter. Morawska et al. [21] focused on vehicle produced ultrafine particles and discussed limitations of measurement methods, sources, characteristics, transport and exposure of these particles in urban environments. Their further review focused on indoor and outdoor monitoring of airborne nanoparticles [3]. Morawska [22] discussed the importance of airborne ENPs from the health perspective. Regulations and policy measures related to the reduction of ambient particulate matter were discussed in their follow-up article [23], Their recent review article discussed the commuters exposure to ultrafine particles and associated health effects [24]. 

Airborne nanoparticles empirically fit well to log normal distributions and exhibit bimodal distributions in atmospheric urban environments. These arise from both natural and anthropogenic sources. Road vehicles remain a dominant source, contributing up to 90% of total PNCs, in polluted urban environments. 

ENPs are emerging class of airborne nanoparticles having a main impact on the air quality of indoor environments these are unintentionally released into the ambient environment during the manufacture (commercial or research), handling, use or disposal of nanomaterials integrated products. Their physical and chemical characteristics differ from other nanoparticles produced through traffic [4], The health consequences of their inhalation are not yet well known. A number of studies have reported their number concentrations and size distributions in workplaces but their concentrations in ambient urban environments are largely unknown and warrant further research. Adequate methods have yet to be developed to quantify them in the presence of nanoparticles from other sources. 

Non-thresholded chemicals that are not carcinogens are less frequently identified. For many years lead was considered to be thresholded because its effects on haemoglobin synthesis were not seen at low doses. However, recent work into the effects of lead on mental development suggest that there may be no threshold for this end-point. Food is a relatively minor source of lead exposure compared with air and dust in urban environments. For chemicals that relate to toxicological end-points that do not show thresholds it is not possible to identify a NOAEL or PTWI. In such cases it is desirable to estimate the level of risk associated with a given level of exposure. 

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. 

Figure 8.1 Regional and local anomaly threshold applied to an urban environment. The concentration graph shows the influence of anthropogenic sources (industrial area, downtown and main roads) on pollutant distribution in soils.

It is obvious from this table that the concentrations of non-ortho CBs and, to a certain extent, mono-ortho CBs are extremely low (< ppq). On the other hand, di-ortho CBs are measurable. In general, PCB concentrations are higher in rain, well, tap, and bottled waters which are close to a contamination source (urban environment) [123-126], Congener-specific reports of PCBs in inland lakes such as Great Lakes and Baikal have been published [117,127]. 

Atkinson, Pitts, and coworkers at the University of California at Riverside are in the process of publishing a series of papers on NO3 chemistry. I will briefly describe a few of their results. Their method involves the use of a smog chamber experiment with long path infrared absorption measurements of reactant concentrations [26]. Their kinetic measurements are based on the competition between two different reactants for the NO3 radical. N2O5 is used as a source of NO3. Table 2 summarizes some of their data for reactions of NO3 with selected organic compounds. Most of these materials are present in significant concentrations only in polluted urban environments. For the alkene compounds the rate coefficients follow the general trend found few the addition reactions of O and OH. This supports the proposal that the mechanism involves addition to the double bond. A dramatic increase in reactivity is observed with the... 

Venetsanos, A., Huld, T., Adams, P., Bartzis, J. (2003). Source, dispersion and combustion modelling of an accidental release of hydrogen in an urban environment. /. Hazardous Mat. A105,1-25. 

Two major sources of salinity are important in the urban environment sewage and road salt. The salinity of domestic wastewater is derived from both the salinity of the source water supply to the municipality and the salts added directly by humans (Figure 11). This includes the use of detergents, washing powders, and salts. In Israel, for example, the average net human contributions of chloride, sodium, and boron to domestic wastewater are 125 mg, 120 mg, and 0.6 mg. 

Particulates are another source of respiratory irritation when inhaled. In urban environments, diesel exhaust particles and fly ash residue from power plant oil combustion are the main contributors of respirable particulates of less than 10 pm diameter (PM 10). These contain mixtures of lipo-philes and hydrophiles including various metals, acid salts, aliphatic hydrocarbons, PAHs, quinones, nitroaromatic hydrocarbons, andaldehydes. 151 Diesel combustion particulates contain large surface areas that can adsorb large quantities of organic compounds and deliver these to respiratory tract tissue. Other inhaled particulates can adhere to lung surfaces and adsorb and bond other vapors that are inhaled, thereby increasing their toxicities. PM2.5 particulates (those with diameters of less than 2.5 pm) that reach the lower respiratory tract as far as the alveoli are more toxic than PM 10 particulates of the same composition. 16 ... 

No additional examples of intense heat sources or actual fires released within model forest or simulated urban environments are known to this author. 

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. 

Shah and Singh (1988) collected indoor and outdoor data for volatile organic chemicals from both residential and commercial environments. The average daily outdoor concentration of formaldehyde for all outdoor site types (remote, rural, suburban, urban, and source-dominated) was 8.3 ppbv the average daily indoor concentration of formaldehyde was 49.4 ppbv. 

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