Use of factor analysis to differentiate pollutants from other trace metals in surface soils of the mineralized area of Madison county, Missouri, USA

Barium, Be, Co, Cr, Cu, Li, Mn, Ni, Pb, Sr, and V concentrations were determined in 97 surface soil samples collected 1000 m apart on a regular grid in Madison county, Missouri, U.S.A. The data were normalized by a log sub(10) transformation and a matrix of correlation coefficients computed. Strong correlations were observed between several metals and statistically significant correlations were found between others. The data were then analyzed by R-mode factor analysis. Three factors satisfactorily explained the data variance and were interpreted as follows. Factor 1 (55% variance) comprised a group of elements which contaminated local soils as a consequence of operations connected with non-ferrous metal mining. Factor 2 (33% variance) contained elements which accumulate in soils during weathering. The remaining elements were grouped together in factor 3 (12% variance) and here soil contents appeared to be controlled by rock composition.