Urban particles

Note that the chemical dimensions do not yield such robust "markers", or tracers, as the isotopic dimensions. For a given combustion source, for example, one is apt to find chemical--but not isotopic—fractionation varying significantly with time, particle size, particle history (differential volatilization or reaction), etc. The ratio K/Fe, for example, was quite different in the fine and coarse fractions from a slash burn (1.5 vs. 0.3) [33] and Pb/Br, which has been popular as an automobile exhaust tracer, varies with the "age" of urban particles [22]. 

Litschke T, Kuttler W (2008) On the reduction of urban particle concentration by vegetation -a review. Meteorol Z 17(3) 229-240... 

Weber S (2009) Spatio-temporal covariation of urban particle number concentration and ambient noise. Atmos Environ 43 5518-5525... 

The presence of this non-exchangeable pool for PAHs is implied by the results of experiments which compared the extraction rates of native PAHs and spiked perdeuterated compounds from SRM 1649 urban dust (Burford et al., 1993). Extraction with supercritical C02 quantitatively recovered the deuterated PAHs within 30 min. C02 alone removed native PAHs more slowly and incompletely, C02/ methanol gave improved yields. Differences in volatilization of PAHs from urban particles into a clean airstream occurred, depending on whether the PAHs were native to the particles or added by surface coating (Poster et al., 1995). 

Rauch, S., Morrison, G.M., Moldovan, M. Scanning laser ablation-ICP-MS tracking of platinum group elements in urban particles. Sci. Total Environ. 286, 243-251 (2002)... 

Water-soluble organic compounds in urban atmospheric particles can also contain organosulfur compounds. Methanesulfonic acid and hydroxymethanesulfonic acid have been found as the major organosulfur compounds in urban aerosols, most particularly in particles with the diameter range of 0.43-1.1 p.m. Monomethyl hydrogen sulfate has also been detected on urban particles from localities where no oil or coal power plant exist (Suzuki et al., 2001). 

The sources and chemical compositions of the fine and coarse urban particles are different. Coarse particles are generated by mechanical processes and consist of soil dust, seasalt, fly ash, tire wear particles, and so on. Aitken and accumulation mode particles contain primary particles from combustion sources and secondary aerosol material (sulfate, nitrate, ammonium, secondary organics) formed by chemical reactions resulting in gas-to-particle conversion (see Chapters 10 and 14). 

Mauad T, Rivero DHRF, de Oliveira RC et al (2008) Chronic exposure to ambient levels of urban particles affects mouse lung development. Am J Respir Crit Cate Med 178 721-728 Mazzarella G, Ferraraccio F, Prati MV et al (2007) Effects of diesel exhaust particles on human lung epithelial cells An in vitro study. Respir Med 101 1155-1162 McClellan RO (2000) Particle interactions with the respiratory tract. In Gehr P, Heyder J (eds) Particle-lung interactions, 1st edn. Marcel Dekker, New York Mills NL, Ttimqvist H, Gonzalez MC et al (2007) Ischemic and thrombotic effects of dilute diesel-exhaust inhalation in men with coronary heart disease. N Engl J Med 357 1075-1082 Mills NL, Robinson SD, Fokkens PHB et al (2008) Exposure to concentrated ambient particles does not affect vascular function in patients with coronary heart disease. Environ Health Perspect 116 709-715... 

Urban levels of air pollution (downtown Sao Paulo) modified the progression of urethane (3 g/ kg)-induced lung tumours in mice (Cury etal. 2000). Urban particles consist of three modes ul-trafine particles, accumulation mode particles (which together form the fine particle mode) and coarse mode particles. Ultrafine particles (those of <100nm diameter) contribute very little to the overall mass, but are very high in number, which in episodic events can reach several hundred thou-sand/cm in the urban air. The hypothesis that ultrafine particles are causally involved in adverse responses seen in sensitive humans is based on several studies summarised by OberdOrster (2001). Timblin etal. (2002) demonstrated the development of dose-related proliferation and apoptosis after exposure of an alveolar epithelial cell line (CIO) to particulate matter or to ultrafine carbon black, a component of particulate matter. Ribonuclease protection assays demonstrated that increases in mRNA levels of the early response protooncogenes c-jun, junB, fra-l, and/ra-2 accompanied cell pro-hferation at low concentrations of particulate matter whereas apoptotic concentrations of particulate... 

Zhang Q, Jimenez JL, Worsnop DR, Canagaratna M (2007) A case study of urban particle acidity and its influence on secondary organic aerosol. Environ Sci Technol 41 3213—3219... 

Fig. 5. Size distributions of atmospheric particles ia (—) urban, (------) mral, and (------) remote background areas.

Fig. 6. Size distribution of an urban aerosol showing the three modes containing much of the aerosol mass. The fine mode contains particles produced by condensation of low volatility gases. The mid-range, or accumulation mode, results from coagulation of smaller aerosols and condensation of gases on preexisting particles. Coarse particulates, the largest aerosols, are usually generated mechanically.

When a liquid or solid substance is emitted to the air as particulate matter, its properties and effects may be changed. As a substance is broken up into smaller and smaller particles, more of its surface area is exposed to the air. Under these circumstances, the substance, whatever its chemical composition, tends to combine physically or chemically with other particles or gases in the atmosphere. The resulting combinations are frequently unpredictable. Very small aerosol particles (from 0.001 to 0.1 Im) can act as condensation nuclei to facilitate the condensation of water vapor, thus promoting the formation of fog and ground mist. Particles less than 2 or 3 [Lm in size (about half by weight of the particles suspended in urban air) can penetrate the mucous membrane and attract and convey harmful chemicals such as sulfur dioxide. In order to address the special concerns related to the effects of very fine, iuhalable particulates, EPA replaced its ambient air standards for total suspended particulates (TSP) with standards for particlute matter less than 10 [Lm in size (PM, ). 

The number of particles varies considerably with time and place (Table 9.1). To reduce the number of particles in the urban environment to the same number as in the countryside, a filter with 99.9% separation is required. An... 

A large number of odors are borne by particles, but for effective separation, chemical filters are very often required, which can be justified in an urban environment. 

The presence of the electrolyte is required to provide a pathway for the current and, in urban areas, this is commonly ironfll) sulfate formed as a result of attack by atmospheric SO2 but, in seaside areas, airborne particles of salt are important. Because of its electrochemical nature, rusting may continue for long periods at a more or less constant rate, in contrast to the formation of an anhydrous oxide coating which under dry conditions slows down rapidly as the coating thickens. 

One example of normal-phase liquid chromatography coupled to gas chromatography is the determination of alkylated, oxygenated and nitrated polycyclic aromatic compounds (PACs) in urban air particulate extracts (97). Since such extracts are very complex, LC-GC is the best possible separation technique. A quartz microfibre filter retains the particulate material and supercritical fluid extraction (SPE) with CO2 and a toluene modifier extracts the organic components from the dust particles. The final extract is then dissolved in -hexane and analysed by NPLC. The transfer at 100 p.1 min of different fractions to the GC system by an on-column interface enabled many PACs to be detected by an ion-trap detector. A flame ionization detector (PID) and a 350 p.1 loop interface was used to quantify the identified compounds. The experimental conditions employed are shown in Table 13.2. 

An average adult breathes about 8.50 X 103 L of air per day. The concentration of lead in highly polluted urban air is 7.0 X 10 6 g of lead per one m3 of air. Assume that 75% of die lead is present as particles less than 1.0 X 10 6 m in diameter, and that 50% of die particles below that size are retained in the lungs. Calculate the mass of lead absorbed in this manner in 1 year by an average adult living in this environment... 

Fig. 1. The size distribution of particles in an urban atmospheric dust showing the three size modes. Based on Whitby, 1977 4).

Over 65% of the global population Is living In urban areas where the concentration levels of particles are considered to be unacceptably high. In contrast less than 20% of the people are living In cities considered to have acceptable levels of particles. 

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