Analytical Results and Chemometric Interpretation

The amounts of 16 elements (see also Tab. 7-1) were determined with the above mentioned method of emission spectrographic analysis in a total of 170 samples of sedimented airborne particulates from three urban areas (Gera, Jena, and Greiz) in Thuringia (Germany) during one year of investigation. 

The routine analytical method applied is relatively inaccurate in respect of the absolute values, but sufficiently accurate for determination of element correlations in the following multivariate statistical computations. 

To demonstrate the accuracy, two dust and two soil reference materials were analyzed with the described method. The mean value of the correlation coefficients between the certified and the analyzed amounts of the 16 elements in the samples is r = 0.94. By application of factor analysis (see Section 5.4) the square root of the mean value of the communahties of these elements was computed to be approximately 0.84. As frequently happens in the analytical chemistry of dusts several types of distribution occur [KOM-MISSION FUR UMWELTSCHUTZ, 1985] these can change considerably in proportion to the observed sample size. In the example described the major components are distributed normally and most of the trace components are distributed log-normally. The relative ruggedness of multivariate statistical methods against deviations from the normal distribution is known [WEBER, 1986 AHRENS and LAUTER, 1981] and will be tested using this example by application of factor analysis. 

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