Water quality assessment of the Jaibaras River, Ceará, Brazil using principal component analysis.

Abstract

Multivariate statistical techniques, Factor Analysis/Principal Component Analysis – FA/PCA, was applied to the data set on water quality of the Jaibaras River, Ceará, Brazil to identify the most significant pollution sources/factors. The data set was generated during three years (Apr/2002 to Jun/2005) monitoring at two sites (P1 - Ayres de Souza water gate and P2 - the outlet of the Jaibaras River). It was analyzed the following variables: pH, EC, Na+, Ca+2, Mg+2, K+, Cl-, HCO3-, PO4-2, NH+4, NO3-, SO4-2 and Sodium Absorption Ratio (SAR). At the P1, three principal components were extracted, explaining 80% of the data variance. The first factor was mainly assigned to mineralization, while the others factors were built from variables indicative of pollution. At the P2, FA/PCA showed the existence of two factors which account to 81% of the total variance, and water quality were mainly influenced by nitrate, fertilizers and waste (human actions). The FA/PCA reflected the physicochemical and pollution characteristics of the water quality in the Jaibaras River.