Qualidade da água e sedimentos em canais urbanos na cidade de Belém, Amazônia oriental.

Abstract

Urbanization and industrialization have impacted many Amazonian cities, including Belém, particularly due to the improper disposal of effluents and waste, which compromise water quality and cause contamination by potentially toxic elements (PTEs). This study aimed to characterize water quality parameters, determine PTEs concentrations, and assess associated risks in water and sediments from urban channels in Belém, eastern Amazon. Samples were collected at 162 points (81 water and 81 sediment), including 152 from channels in ten anthropized basins: Armas - ARM, Estrada Nova - ENO, Icoaraci - ICO, Mata Fome - MTF, Murucutum - MUR, Paracuri - PCR, Tamandaré - TAM, Tucunduba - TUC, Una - UNA, and Val-de-Cans - VAL; and ten from a reference water body - RWB. Water properties were measured using a multiparameter probe, analyzing temperature, pH, dissolved oxygen (DO), total dissolved solids (TDS), and electrical conductivity (EC). PTEs concentrations were determined by microwave plasma atomic emission spectrometry (MP-AES) and compared to the limits set by CONAMA Resolutions 357/2005 and 454/2012. Data were statistically analyzed using Kruskal-Wallis and Dunn tests (p < 0.05). Physicochemical parameters varied among basins, suggesting different levels of anthropogenic impact. Areas with greater vegetation cover showed lower temperatures and higher DO levels, while more urbanized areas exhibited higher pH, lower DO, and higher EC and TDS values. Concentrations of Cd, Co, and Cu in water exceeded legal limits in several basins, indicating anthropogenic contamination and potential ecological risk, according to freshwater standards (Class II). In sediments, Cd, Cu, Pb, and Zn exceeded Level 1 of CONAMA Resolution 454/2012 in urban areas, pointing to ecotoxicological risk. The ARM, ICO, MTF, TAM, and TUC basins showed contamination levels requiring attention, especially for Ni and Pb. Cd posed a high ecological risk in the TAM basin, emerging as the most concerning element. Mn, Na, Ni, and Pb showed significant enrichment. The results of this study reinforce the need for public policies focused on effluent treatment, urbanization control, and environmental recovery. Effective and ongoing projects could mitigate environmental impacts and protect water quality and urban ecosystems in Belém.