Analysis of factors influencing changes of drinking water chemical composition

Drinking water samples were collected from 501 points in five cities located in south Poland - Kraków, Myszków, Jaworzno, Racibórz and Kamienna Góra, using the random daytime sam-pling method (RDT). All samples were collected by trained samplers from randomly chosen buildings, at random hours and without prior flushing. Analysis of chemical composition of water samples was conducted at the certified Hydrogeochemical Laboratory of AGH - University of Science and Technology in Kraków. Concentrations of selected trace elements (As, Cr, Zn, Al, Cd, Mn, Cu, Ni, Pb, Fe) and major ions (Na, Ca, Mg, K, Cl-, SO42-, HCO3¯) were measured. The principal component analysis was performed. The dimension reduction was made on the basis of major ions. Two principal components were used: the first one was dependent on the concentration of Cľ , SO42-, NaandK, and the second one included the concentration of Mg, Ca and HCO-. The analysis indicated a diversity of the results in virtue of sampling site. Three groups of results were clearly indicated: the first one represented water samples from Kraków and Kamienna Góra, the second one - samples from Myszków and Racibórz, and the third group was were the samples collected in Jaworzno. This diversity results from the type of water intake (groundwater and surface water), manner of water water supply systems