Avaliação sazonal da qualidade das águas superficiais em áreas portuárias estuarinas da região metropolitana de Belém - Pa

Abstract

This dissertation investigated the seasonal variation in surface water quality in estuarine port areas of the Metropolitan Region of Belém (PA), focusing on the terminals operated by the Companhia Docas do Pará (CDP) in Belém, Miramar, Outeiro, and Vila do Conde (Barcarena). The study, conducted between October 2021 and July 2023, analyzed physicochemical (pH, dissolved oxygen, turbidity, conductivity, total dissolved and suspended solids, salinity, sulfate) and microbiological parameters (total coliforms, thermotolerant coliforms, and Escherichia coli), considering the influence of the rainy and less rainy seasons, as well as the tidal cycle. The results revealed a continuous and severe state of environmental degradation, characterized by recurrent non-compliance with the standards established by CONAMA Resolution No. 357/2005 for Class 2 freshwaters. Dissolved oxygen levels were frequently below 5 mg L⁻¹, pH was predominantly acidic (averages between 5.67 and 6.73), turbidity and suspended solids increased significantly during the rainy season (up to 62.28 NTU at the Port of Belém), and a sharp rise in electrical conductivity (average of 502.14 μS cm⁻¹) and salinity (maximum of 1.75) was observed during the dry season, indicating saline intrusion in terminals closer to the estuary mouth. Microbiological contamination from domestic sewage was the most critical aspect, with thermotolerant coliform averages reaching up to 39,466 MPN/100 mL at the Miramar Terminal, exceeding the legal limit of 1,000 MPN/100 mL by nearly 40 times. The application of the Tukey statistical test showed that the tidal cycle (flood and ebb) did not exert a significant influence on the evaluated parameters, suggesting a pollutant load so constant and high that natural hydrological dynamics do not promote effective dilution. It is concluded that the surface waters in the studied port areas exhibit compromised quality due to chronic anthropogenic pressures, with the self-purification capacity of the estuarine system exceeded. The results underscore the urgency of investments in basic sanitation, the adoption of more sustainable port practices, and the strengthening of continuous and integrated environmental monitoring programs, aiming to protect aquatic ecosystems and public health in Eastern Amazonia.