Statistical analysis of ground water distribution in Alessandria Province (Piedmont-Italy)

29 chemical and physical-chemical features of water samples from 44 wells were analysed by multivariate statistical tools to provide the characterisation of the ground water distribution of the North-West area of Alessandria province (Piedmont-Italy). The 29 parameters determined include: temperature, pH, conductivity, dissolved oxygen, suspended solids, COD, total hardness, total phenols, fats and oils, non-ionic surfactants, chlorinated solvents, total chromium, P₂O₅ and several cations and anions (NO₃^-, NH₄⁺, Ca₂⁺, Na⁺, K⁺, Mg²⁺, Cl^-, SO₄^2-, SO₃^2-, S^2-, Fe³⁺, Mn²⁺, Zn²⁺, Al³⁺, Ni²⁺, Pb²⁺). The sampling took place during the spring and summer 2001. The use of Principal Component Analysis together with refined mapping tools (kriging methods) provided a description of the area investigated with respect to the characteristics of the subterranean waters. A significant difference in water composition has been highlighted between small villages (with a probable human polluting effect) and zones far from the built-up areas. Cluster analysis was also performed in order to evaluate the different wells similarity and confirmed the results obtained by Principal Component Analysis.