Extinction coefficient chemical species contributions

Ouimette, J.R., (1980) "Chemical Species Contributions to the Extinction Coefficients," Thesis, Ph.D.,... 

In a separate study ( ) aerosol species mass distributions were successfully used to calculate the contribution of each species to the extinction coefficient. Unfortunately, such detailed data is not usually available. At most air monitoring stations, only the total aerosol species mass concentrations, M -, are determined from filter samples. Statistical methods have been used to infer chemical species contributions to the particle light extinction coefficient ( ). For such analyses it is assumed that bgp can be represented as a linear combination of the total species mass concentrations, M-j, viz.. 

Ouimette, J.R. Aerosol Chemical Species Contribution to the Extinction Coefficient, Ph.D. Thesis, California Institute of Technology, July 1980. 

The contributions of aerosol chemical species to the extinction coefficient can be estimated from knowledge of their mass distributions, densities, and refractive indices. It is assumed that the particles can be represented as spheres. For a mixture in which the composition is a function of particle size and all particles of a given size have the same composition, defined here as a specific mixture, the contribution of species i becomes (4 ) ... 

Table 15.3 presents estimated contributions of chemical species to the wintertime extinction coefficient in Denver, Colorado about 1980. We note, for example, that in... 

TABLE 15.3 Contribution of Chemical Species to the Extinction Coefficient 6ext in Denver Wintertime... 

Table 22.3 presents estimated contributions of chemical species to the wintertime extinction coefficient in Denver, Colorado about 1980. We note, for example, that in Denver during winter, elemental carbon was responsible for about 40% of visibility reduction. The disproportionately large influence of black carbon upon light extinction, relative to its concentration, arises in part, as we will see, because black carbon is more effective than nonabsorbing aerosol particles (such as sulfates and nitrates) of the same size in attenuating light (Faxvog and Roessler, 1978). 

As discussed previously (Sec. II.D.4), acquisition of a quantitative NMR spectrum presupposes careful planning. NMR offers several advantages over other techniques, such as infrared spectroscopy, for the determination of copolymer composition. First, in a truly quantitative NMR spectrum, the relative areas of all peaks are self-consistent, so that if the intensity of peak A is twice that of peak B, it is certain that the number of nuclei contributing to A is double that of B. In other words, there is no NMR equivalent of an extinction coefficient, and precharacterized standards are not needed for method development, if the experiment is properly designed and executed. Second, because of NMR s great sensitivity to subtle structural changes, even chemically similar species can be distinguished. It is, for example, possible to calculate the eoncentration of each pendant-... 

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