POLLUTION OF A RIVER BASIN AND ITS EVOLUTION WITH TIME STUDIED BY MULTIVARIATE STATISTICAL-ANALYSIS

A set of quantitative analytical data for 13 rivers belonging to the b asin of the Tanaro (Piedmont region, north-western Italy) has been pro cessed by multivariate statistical techniques. The original matrix, wh ich refers to the year 1990, consisted of 20 chemical and physico-chem ical variables, determined at 44 sampling sites. The following methods have been used for the treatment of the data: cluster analysis (unsup ervised pattern recognition), factor analysis, variable selection by F isher weights. A comparison has also been made between the data referr ing to 1990 and to 1978 in order to investigate the evolution of the e nvironmental situation for the Tanaro basin after such a lapse of time . This comparison has been carried out by processing the 3-D matrix wh ich collects the data of the two different periods.