Avaliação integrada da qualidade da água por Análise de Componentes Principais e Índice de Poluição por Metais Pesados na Bacia do Murucutu, Belém (PA), Amazônia brasileira

The Murucutu Basin is an important source of water supply for the Metropolitan Region of Belém, encompassing the Utinga State Park and the Bolonha and Água Preta reservoirs. This study presents, for the first time, the analysis of 40 surface water samples regarding metal concentrations (Al, Cr, Mn, Fe, Ni, Cu, Zn, As, Ba, and Pb) and basic physicochemical parameters. The results indicated that Cr, Ni, Cu, Zn, As, Ba, Pb, and turbidity were within the limits established by CONAMA Resolution No. 357/2005 and the World Health Organization, whereas pH, Fe, Mn, and Al occasionally exceeded the recommended thresholds. The Heavy Metal Pollution Index (HPI) classified all samples as having excellent water quality, providing an integrated assessment of metal contamination. Despite this favorable classification, the integrated application of Principal Component Analysis (PCA) and HPI allowed a more comprehensive interpretation of water quality, highlighting the influence of hydrological seasonality and natural geochemical processes on metal variability. PCA revealed a relevant contribution of elements such as Al and Fe, predominantly associated with geogenic sources, whose importance may be attenuated when assessed solely through synthetic indices. These findings establish a baseline for the basin, demonstrate seasonal variability, and indicate that integrating multivariate techniques with water quality indices is essential to avoid oversimplified interpretations of water quality in tropical basins.