Aerosol particles organic fraction

Recommended Values of Aerosol Particle Volume Fraction in Air VylVK, dimensionless) and Volume Fraction of Organic Matter in Aerosols dimensionless) for Different Environmental Scenarios... 

Clearance to pulmonary lymph nodes will occur at a fractional rate of 0.0001 per day. Dissolution of the deposited particles and absorption of cerium into the systemic circulation will occur at rates that are between the extremes represented by CeCh in CsCl particles and Ce oxide or Ce in fused aluminosilicate particles as given by the functions included in Figure 9. These rates should not be expected to be constant over the entire clearance period and will depend upon the overall composition of the bulk aerosol particles, which indude particle size, amount of stable lanthanide present, acidity, and the solubility of other components of the particles. The accuracy of predicting respiratory tract clearance and internal organ uptake of radiocerium will depend heavily upon adequate determination of the particle solubility characteristics. 

The reviews Toxicological Indications of the Organic Fraction of Aerosols A Chemist s View by Van Cauwenberghe and Van Vaeck (1983) and Atmospheric Reactions of PAH by Van Cauwenberghe (1985) provide critical assessments and extensive literature references of the status of research to 1985 in the complex area of heterogeneous photochemical reactions and of the interactions of PAHs on laboratory substrates, primary combustion particles, and ambient particulate matter with ozone and NOz in air. In the following sections, we briefly summarize results from this earlier era and address subsequent studies on heterogeneous atmospheric reactions of PAHs in simulated and real atmospheres. 

Mediterranean Basin. Additional studies of the finer particle fractions and chemical characterisation will elucidate the sources and impact of particle pollution in the area. Particularly there is a lack of data on carbonaceous aerosol that organic and elemental carbon observations could help to distinguish the contribution of secondary versus primary sources. 

The organic fraction present in atmospheric particles is a highly complex mixture, which makes the speciation of individual compounds a difficult task. The traditional analytical approach has usually been solvent extraction of aerosol particles collected in a filter followed by gas chromatographic separation coupled to mass spectrometry (GC-MS) detection for individual compound identification and quantification. Although a large number of compounds, sometimes in trace amounts, have been... 

Ice particle measurements in the expansion experiment with 40% OC soot aerosol markedly differ from the 16% OC sample. Note that the optical particle spectrometer hardly detects any ice particles. Additionally, extinction signatures of ice are barely visible in the infrared spectra and diere is only a weak intensity increase of the back-scattered laser light in course of the expansion. The number concentration of ice crystals is less than 10 cm, thus < 1% of the seed aerosol particles act as deposition ice nuclei. In contrast to the 16% OC experiment, no precise critical ice saturation ratio can be specified for the 40% OC soot sample. RHi continues to increase to 190% because very little water vapour is lost on the small surface area of the scarce ice crystals. In summary, die comparison of the two expansion experiments provides first evidence that a higher fraction of organic carbon notably suppresses the ice nucleation potential of flame soot particles. 

The Ni contents of the four fractions are determined by ETAAS. Vincent et al. (2001) used a similar approach based on differential step-wise leaching of nickel from aerosol particles that had been fractionated with a cascade impactor. For fractionation of nickel species in natural waters, Mandal et al. (2002) used Chelex-100 as a competing ligand to measure the rate of Nk released by dissociation of nickel in dissolved organic carbon complexes. 

Finally, a number of gas-phase chemical reactions, such as the oxidation of selected organic compounds, generate nonvolatile condensable products that associate with aerosol particles. A large fraction of the aerosol consists of ammonium sulfate, which derives fi om the oxidation... 

A characteristic of old diesel engines was black soot in their exhausts caused by the combustion process itself in which very small atomized droplets of fuel burning in hot compressed air left an unbumt core of fine carbon particles onto which other species in the exhaust gas adsorbed [26-28]. The total particulate matter emissions of diesel exhaust are comprised of three main components. One component is the solid carbonaceous fraction, which is the visible soot emissions commonly associated with diesel exhaust A second component is the soluble organic fraction (SOF). The SOF can exist either as a vapor or as an aerosol depending of the temperature of the diesel exhaust These liquids arise from imbumed or partially burned diesel fuel or lubricating oil swept from the cylinder walls of the engine [29]. 

The coefficient 5(m octanol/m aerosol particles) is directly proportional to the fraction of available organic matter in aerosols (fou), the ratio of densities of aerosol particles and octanol (pp/po), the ratio of molecular weights of octanol and organic matter (Mq/Mom), and the ratio of activity coefficients of the chemical in octanol... 

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