Three-way principal component analysis of chemical data from Lake Como watershed

A large data set obtained by a one-year monthly determination of ions (F−, Cl−, Br−, NO3−, NO2−, PO43−, SO42−, Na+, K+, Ca2+, Mg2+, NH4+) and trace metals of environmental concern (Ni, Co, Mn, Fe) from the tributaries of Lake Como (Lombardy, Northern Italy) was treated by three-way Principal Component Analysis. The results showed that the chemical features of the investigated rivers are mainly related to the lithology of the watershed. Some cases of contamination were evidenced and rationalized on the basis of anthropic pollution or on the basis of the geochemical features of the territory. The method here proposed allows an easy and quick interpretation of the chemical data by means of graphical devices. The information extracted by the three-way models would be very useful to regional agencies in developing a strategy to manage water resources in the whole basin of Lake Como.