Tires particles/emissions

In all of these systems, the rate of generation at the gas-solid interface is so rapid that only a small fraction is canied away from the particle surface by convective heat uansfer. The major source of heat loss from the particles is radiation loss to tire suiTounding atmosphere, and the loss per particle may be estimated using unity for both the view factor and the emissivity as an upper limit from tlris source. The practical observation is that the solids in all of these methods of roasting reach temperatures of about 1200-1800 K. 

The 3.5- and 8-ntn nanoparticles show well-resolved peaks at 362 and 473 nm, respectively, as well as other features at higher energies. The 4.5-nm particles show a well-resolved peak at 400 nm and a shoulder at 450 nm. It is tempting to assume that in each case, the lowest energy absorption corresponds to the lowest allowed transition (the A exciton) in bulk M0S2. Polarization spectroscopy can be used to determine if this is the case. The lowest allowed transitions in bulk material, the A and B excitons, are polarized perpendicular to the crystallographic c axis. If the lowest allowed transition correlates to the A exciton, then it would be expected to also be a planar (xy polarized) oscillator. However, tire results of polarization studies reveal that the actual situation is more complicated. A combination of time-resolved polarized emission and one-color time-resolved polarized absorption (transient bleach) studies facillitate assignment of the polarizations of the observed nanoparticle transitions. The 3.5-nm particles are emissive and the polarization of the several of the lowest transitions may be determined... 

The 8- and 4.5-nm particles are at most weakly emissive and the polarizations of spectral features assigned to these particles are determined by polarized bleach measurements. The bleach anisotropy was determined using femtosecond pulses, with the probe delayed a few picoseconds from the pump. This delay ensures electronic and vibrational relaxation as well as relaxation of optical Kerr effects induced in tire solvent. As a control, transient absorption experiments were performed with excitation at 475 nm and detection at 550 nm. This detection wavelengtli is to the red of the wavelengths at which a bleach would be observed and provides a measure of the transient absorption intensity in this general spectral... 

Dahl A, Gharibi A, Swietlicki E, Gudmundsson A, Bohgard M, Ljungman A, Blomqvist G, Gustafsson M (2006) Traffic-generated emissions of ultrafine particles from pavement-tire interface. Atmos Environ 40 1314—1323... 

The effect of burning tires or TDF in waste-wood (hog fuel) boilers in pulp and paper mills was generally unfavorable on the emissions. Particulates increased in every series of tests when the TOF percentage was increased. The reason for this is pr ably due to the type of emissions control devices used on hog fuel boilers venturi scrubbers. The effectiveness of venturi scrubbers decreases as the particle size in the emission decrease. Zinc oxide is used in the manufacture of tires, and is present in significant quantities in scrap tires. Zinc oxide has a relatively low vaporization temperature and is vaporized when tires are burned. When zinc oxide vapors condense, they form sub micro-sized particles that are too small to be removed with a venturi scrubber. This is verified by comparing the zinc emissions in hog-fuel boilers to baseline. Zinc emissions increased in most cases 300 percent (and in one case, almost 50 times the base line emission rate). The effect of burning tires on other pollutants was mixed, and distinctive trends could not be determined. 

However, venturi scrubbers do not perform well when the process is burning tires or TDF. As noted earlier, the efficiency of venturi scrubbers decreases as particle size decreases and emissions from tires and TDF contain pollutants that are too small to be removed by venturi scrubbers. 

Zinc in the atmosphere is primarily in the oxidized form in aerosols (Nriagu and Davidson 1980). Zinc is found in particles of various sizes, the size being determined by the source of zinc emission. Waste incinerators release small zinc-containing particles to the atmosphere, whereas wear of vehicle tires produces large particles (Sohn et al. 1989). The particle sizes of zinc dusts in ambient air are on the whole small 52-70% have diameters <5 pm (VDI 1995). 

Transportation source emissions occur in two categories (1) vehicle exhaust and (2) vehicle-related particles from tire, clutch, and brake wear. Engine-related particulate emissions are composed primarily of lead halides, sulfates, and carbonaceous matter and are mostly smaller than 1 )U,m in diameter. About 40% of particles from tire wear are less than 10 fxm (about 20% are less than 1 /xm) and are primarily carbon. Particles from brake linings are less than 1 fxm and are composed mainly of asbestos and carbon. 

Emissions from motor vehicles are among the major contributors to fine particle concentrations in the urban atmosphere (Schauer et al. 1996 Kleeman et al. 2000) they make substantial direct and indirect contributions to ambient PM levels. Direct particulate emission sources from vehicles include their exhaust (Mulawa et al. 1997 Sagebiel et al. 1997), the mechanical wear of tires and brakes (Rogge et al. 1993 Garg et al. 2000), and the ejection of particles from the pavement (Kupiainen et al. 2005) and unpaved road shoulders (Moosmiiller et al. 1998) as well as re-suspension processes (Nicholson et al. 1989 Stembeck et al. 2002). Indirect contributions include the emission of reactive gases, both organic and inorganic, which form secondary particulate matter via atmospheric transformations. 

Rubber Tire Wear. Degradation of automobile tires releases carbon black particles to the atmosphere. Carbon blacks are used in tires and contain PAH. No direct emission factor could be established, but the NAS study estimated the annual BaP emissions to be 11 tons per year in the US (3). The total US mileage is approximately 2 10 km per year which gives a BaP emission of 5 yg per km. 

Nuclei with atomic numbers 84. These heavy nuclei, which lie beyond die upper right edge of fhe band of stability, tend to undergo alpha emission. Emission of an alpha particle decreases botii the number of neutrons and the number of protons by 2, moving tire nucleus diagonally toward die belt of stability. 

Gamma ray emission is mostly secondary to alpha, beta, or positron emission or electron capture. When all of the energy is not used by the emission, tire nucleus is in an excited state with energy available for emission. This excitation energy is emitted as a photon when the particle is emitted. In many cases, tire photon will not be emitted rather, it binds to an electron, which is ejected as... 

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