Factor analysis for the study of water resources contamination due to the use of livestock slurries as fertilizer

We investigated the effects of slurry application on water quality in wells , pasture-drainage conduits and rivers. The parameters determined were elec trical conductivity, dry residue, pH, dissolved O-2, NO3-, NO2-, Cl-, Na, P O32- organic matter content, COD, suspended solids, turbidity, colour, Fe, Mn, Cu and Zn. The data were analysed by principal components analysis and cluster analysis. The first axis extracted by principal components analysis of the samples-by-variables matrix represented the degree of dilution of t he water strongly related with saline content; the second axis represented redox conditions, affecting organometallic component. In general, the posit ions of the samples in this factor space reflected the major contamination processes affecting water resources of that type (wells, conduits or rivers ). In the case of rivet-water samples, cluster analysis showed that month o f sampling had a clear effect, reflecting the importance of rainfall. Final ly, in all three water resource types, contamination was most severe in the area of highest Livestock density and highest frequency of slurry applicat ion. (C) 2000 Elsevier Science B.V. All rights reserved.