Source apportionment/general

There are two general types of aerosol source apportionment methods dispersion models and receptor models. Receptor models are divided into microscopic methods and chemical methods. Chemical mass balance, principal component factor analysis, target transformation factor analysis, etc. are all based on the same mathematical model and simply represent different approaches to solution of the fundamental receptor model equation. All require conservation of mass, as well as source composition information for qualitative analysis and a mass balance for a quantitative analysis. Each interpretive approach to the receptor model yields unique information useful in establishing the credibility of a study s final results. Source apportionment sutdies using the receptor model should include interpretation of the chemical data set by both multivariate methods. 

The filter material of choice is a thin teflon membrane since it minimizes artifact formation and maximizes analytical sensitivity by X-ray fluorescence analysis. Although X-ray fluorescence (XRF) may not be the only analytical technique used, it is generally accepted as being the most cost effective analysis for source apportionment. ( 2) Its background and therefore, analytical sensitivity, is dependent on the filters surface density. The analytical sensitivity of XRF for aerosols deposited on a stretched teflon membrane with a density of about 0.3 to 0.4 mg/cm, for example, is about three times greater than an aerosol deposited on a cellulose based filter with a surface density of about 4 mg/cm. This difference can be translated into either more information for the same analytical costs or the same information for a lower analysis cost. 

The symposium was divided into four subject areas, and this volume follows that general format. The first group of chapters reviews and describes many of the recent modeling efforts. The next section is devoted to source characterization studies, while the third group includes chapters concerned with carbonaceous aerosols—both source apportionment and measurement techniques. The final section describes the results of several field studies in areas of the United States and China where wind-blown dust is a serious problem. 

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