Particulate matter definition

Air The composition of gases that make up the earth s atmosphere, approximately 79% nitrogen and 21% oxygen. Pure air has no definite meaning regarding the proportion of these gases this term is used to imply the absence of industrial particulate matter. 

If the blackness of the particulate matter collected on a filter is due to the graphitic carbon content of the sample, then the Km unit should convert to ambient elemental carbon concentrations. The form of that translation is apparent from the definition of the Km unit. Elemental carbon concentration measurements made by laboratory reflactometers calibrated against heated butane soot standards show that elemental carbon concentrations are linearly related to the log of the reflectance ratio R /R. Aerosol loadings stated in Km units should be directly proportional to elemental carbon concentrations sampled. 

Although the results were not definitive, it is clear that substantial amounts of NG passed through both the 1.2- and 0.8-pm filters, although the initial filter retained the bulk in each test. (There were no membrane filters with a pore size less than 0.45 pm in the laboratory at the time of the test. It would have been interesting to repeat the experiment incorporating the smaller pore size filters, such as 0.2 pm.) It is suspected that NG is present as both vapor and particulate matter, the particulate matter having a wide size range. 

There is often a grey area concerning the best definition for small particulate matter. In particular, most structures are automatically referred to as nanoscale materials," fueled by the popularity of the nanotechnology revolution. However, the most precise use of the nano" prefix e.g., nanoparticles) is only for materials with architectural dimensions e.g., diameters, thicknesses, etc.) of less than 100 nm intermediate dimensions between 100 and 1,000 nm should instead be referred to as submicron." CRC Handbook of Chemistry and Physics, 84th ed., CRC Press New York, 2004. 

It is quite ambitious for a scientist to describe a natural phenomenon in terms of a specific reaction. The situation in the atmospheric environment is however more complicated as a variety of reactions are occurring simultaneously and a certain species may take part in different reactions affecting the relative equilibria. Most data are coming from laboratory work and experimental conditions are definitely different from the ones observed in the troposphere. As an example the mechanism of oxidation of sulphur dioxide, in gas phase is usually reported occur to a large extent through free radicals. If the presence of humidity and of particulated matter is considered, specifically in the lower part of the troposphere, definitely also heterogeneous reactions play a very important role. I feel that experiments carried on in the atmosphere yield more consistent results to elucidate the chemistry of the atmospheric environment. 

The key is to design the catalyst in such a way, that it selectively catalyzes the above mentioned oxidation reactions, and that it neither catalyzes the oxidation of NO to NO2, nor the oxidation of SO2 to SO3. The latter reaction needs to be suppressed because, irrespective of environmental concerns and catalyst durability issues, any SO3 formed on the catalyst would react with water and condense as sulfuric acid during the sampling of the particulate matter, therefore increasing the mass of particulates, by their definition. 

Type 1 To assess the present concentrations of substances including pollutants found in the particulate matter and their variations in time and in space (basic surveys), particularly when pollution cannot be definitely shown from water analysis. 

For studies of the atmospheric aerosol, the particles are collected on filters or impactor plates. Although the original definition refers to particles and carrier medium taken together, it is now customary to apply the term aerosol more broadly and to include also deposits of particulate matter. We thus speak of aerosol samples, aerosol mass, etc., a usage... 

In 1988, directive 80/1107/EEC was amended for the last time by EU directive 88/642/EEC [6-4]. It contained several additions concerning the procedure for exposure measurements and setting occupational limit values. The newly implemented annex Ila contained important and useful information on the updated definition of particulate matter (dust, fume, and mist) and on the exposure measurement strategy, with detailed descriptions of sampling conditions, especially for dusts. 

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