Emission Source Characterization

Over the past 15 years, the atmospheric science community has developed a series of mobile platforms with highly accurate and specific fast response instrumentation that have revolutionized atmospheric chemistry field measurements. These include high-altitude aircraft, such as NASA s ER-2 and WB-57, and lower-altitude aircraft like the NASA DC-8, the National Oceanic and Atmospheric Administration (NOAA) and Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) (Naval Postgraduate School) Twin Otters, the National Center for Atmospheric Research (NCAR) C-130, and the DOE Gl. In addition, mobile surface laboratories are now being used for a wide variety of urban and regional air quality and emission source characterization studies.4 Typical configurations for the ER-2 and the mobile laboratory are shown in Figures 1 and 2. 

Stump BW, Johnson LR (1977) The determination of source properties by the linear inversion of sesimograms. Bull. Seismo. Soc. Am. 67(6) 1489-1502 Suaris W, van Mier JGM (1995) Acoustic emission source characterization in concrete under biaxial loading. Materials and Structures 28 444-449... 

The first essential step in the design of a fume control system and selection of gas-cleaning equipment is the characterization of the fume emission source. Design procedures which can be used for new and existing industrial plants follow. The characterization of fume emission sources includes parameters such as plume flow rates (mVs), plume geometry (m), source heat flux (J/s), physical and chemical characteristics of particulates, fume loadings (mg/m ), etc. 

We may thus conclude after this short overview on DeNO technologies that NH3-SCR using catalysts based on V-W-oxides supported on titania is a well-established technique for stationary sources of power plants and incinerators, while for other relevant sources of NO, such as nitric acid tail gases, where emissions are characterized from a lower temperature and the presence of large amounts of NOz, alternative catalysts based on transition metal containing microporous materials are possible. Also, for the combined DeNO -deSO, alternative catalysts would be necessary, because they should operate in the presence of large amounts of SO,.. Similarly, there is a need to develop new/improved catalysts for the elimination of NO in FCC emissions, again due to the different characteristics of the feed with respect to emissions from power plants. 

An important application field of factor and principal component analysis is environmental analysis. Einax and Danzer [1989] used FA to characterize the emission sources of airborne particulates which have been sampled in urban screening networks in two cities and one single place. The result of factor analysis basing on the contents of 16 elements (Al, B, Ba, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Pb, Si, Sn, Ti, V, Zn) determined by Optical Atomic Emission Spectrography can be seen in Fig. 8.17. In Table 8.3 the common factors, their essential loadings, and the sources derived from them are given. 

For purposes of characterization, emission sources are generally divided broadly into stationary and mobile or transportation sources. Stationary sources are further divided into point and area emitters. Typical point sources must include petroleum refineries and electric power plants. Commercial solvent emission and gasoline marketing emission may generally be represented as area sources. A third category has been defined recently—indirect sources—that takes into account hybrid sources like sports arenas and shopping centers. These have fixed locations, but the traffic that is generated by or attracted to such a facility constitutes the source of emission that is combined with the emission of the facility itself. 

Source characterization results are not located in a centralized facility which is constantly updated. The Environmental Protection Agency has established the Environmental Assessment Data System (EADS) (31) which contains chemical compositions of particulate matter emissions tests. This existing computerized structure can provide the centralized location for receptor model source characterization information. Procedures such as those described for ambient data in the previous section need to be developed in order to allow receptor model users access to this data base over telephone lines. The data required of receptor model source tests should be incorporated into the EADS, and source characterization results should report this information in an EADS compatible format. 

The nature of study objectives in environmental research is often multivariate. Several pollutant patterns from different, sometimes unknown, sources may occur. The state of pollution of a sampling point, line, or area in any environmental compartment, whether atmosphere, water, soil, or biota, depends mostly on the nature of the different sources of pollution. Stack emissions are characterized by a multi-element pattern. Waste water effluents contain different contaminants, ranging from heavy metals to cocktails of organic compounds. 

The large variance of the elemental depositions, also demonstrated by the very uncertain temporal courses of the elemental deposition rate (Fig. 7-2), strongly limits visual inspection of the obtained data, the interpretation can be subjective only. Otherwise practically all simple correlation coefficients are significant. Both facts show that it seems to be useful to apply advanced statistical methods to attempt recognition of possible existing data structures which may enable the characterization of pollutant loading and the possible identification of emission sources. 

At this point a characterization technique with a higher chemical resolution is desirable because such functionalization plus surface analytical combination experiments are extremely difficult to perform in a clean and reproducible way. Vibrational spectroscopy such as FT-1R has been developed into such a tool, after several methodical improvements concerning sample preparation and detector sensitivity. In situ oxidation experiments are still very difficult as heated black carbon is a perfect 1R emission source and interferes with any conventional detection in the spectral range of carbon-oxygen fingerprint vibrations. 

Gas Emissivities Radiant transfer in a gaseous medium is characterized by three quantities the gas emissivity, gas absorptivity, and gas transmissivity. Gas emissivity refers to radiation originating within a gas volume which is incident on some reference surface. Gas absorptivity and transmissivity, however, refer to the absorption and transmission of radiation from some external surface radiation source characterized by some radiation temperature 7. The sum of the gas absorptivity and transmissivity must, by definition, be unity. Gas absorptivity may be calculated from an appropriate gas emissivity. The gas emissivity is a function only of the gas temperature Tg while the absorptivity and transmissivity are functions ofboth Tg and Tt. 

Christopher S. J., Hartenstein M. L., Marcus R. K., Belkin M. and Caruso J. A. (1998) Characterization of helium/argon working gas systems in a radiofrequency glow discharge atomic emission source. Part I ... 

Source Characterization and Control Technology Assessment of Methylene Chloride Emissions from Eastman Kodak Company, Rochester, NY... 

Quantitative analyses characterized up to five groups of pollutants with respect to their concentration profiles as the result of input and output processes. In particular the spatial distribution and the intensity of emission sources on the one hand and the environmental stability as well as the tendency to adsorb on the particulate matter on the other hand determined the quantitative occurrence of individual compounds. Nevertheless, accumulation tendencies or elevated concentrations were observed for several contaminants with potential harmful effects (e.g. carbamazepine, brominated phenols, aromatic sulfones and phthalates). 

Haefliger, O. P., Bucheli, T. D., and Zenobi, R., Laser mass spectrometric analysis of organic atmospheric aerosols. 1. Characterization of emission sources. Environ. Sci. Technol, 34, 2178-2183, 2000. 

Jensen B., Wolkoff P. and Wilkins C.K. (1996a) Characterization of Linoleum Identification of oxidative emission processes, characterizing sources of indoor air pollution and related sink effects, ASTM STP 1287, Bruce Tichenor (ed). American Society for Testing and Materials, 145-152. 

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