Principal components analysis rainwater

Two collectors were operated at each site with these paired results statistically screened for potential contamination based on indpendently measured experimental uncertainties. Geographical mapping of rainwater c ncentrations demonstrated a clear enhancement of H, excess SO., and trace metals downwind of the smelter. Principal component analysis revealed the influence of seasalt, crustal material, and a component interpreted to represent smelter S02 and trace metal emissions. 

The approach taken to observe the impact of the copper smelter on mesoscale variations rainwater composition was to determine the spatial, temporal, and experimental components of the variability of a number of appropriate chemical species in the rainwater. This paper presents results for 1985, during smelter operation, and includes (1) estimates of the experimental variability in chemical composition, (2) an approach for a two step chemical and statistical screening of the data set, (3) the spatial variation in rainwater composition for a storm collected on February 14-15, and (4) a principal component analysis of the rainwater concentrations to help identify source factors influencing our samples. 

We have analyzed the rainwater chemical data with multivariate data analysis techniques to identify sources influencing the area covered by our sampling network. Two events were included in the principal component analysis (PCA) the February 15 storm presented here and another storm collected during smelter operation on March 20, 1985... 

Measurement of the experimental uncertainties in our rain sampling procedures and the application of these uncertainties in a screening procedure to eliminate questionable samples from the data set increases the confidence in the interpretation of spatial variations in rainwater composition and of the principal component analysis. Results presented here for a storm collected during smelter operation suggest that it was the major source of the downwind excess SO. elevation above background and the pH depress ion oelow the background value of 5. 

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