Investigação da influência antrópica na concentração de nutrientes inorgânicos dissolvidos no entorno da cidade de Belém-PA

Abstract

Water is one of the most important natural resources, especially in the Amazon context. The disorderly population increase and consequent mismanagement of this resource causes worrying environmental changes in terms of its quality. According to the National Sanitation Information System - SNIS, the northern region of the country treats about 22.0% of the sewage generated and in the Metropolitan Region of Belém, below the national average, with 11.3% of sewage collection. The study area encompasses Guajará Bay and adjacent areas such as the Guamá and Acará rivers. Water collections were carried out during the rainy season (May), in 4 sections divided into left bank (ME), middle (M) and right bank (MD) with surface and bottom collections, every 4 hours for 13 hours to analyze the entire tidal cycle. Parameters were analyzed in situ (Temperature, pH, Eh, electrical conductivity, turbidity, OD, %OD and total dissolved solids) and in the laboratory (Silicate, phosphate, nitrate and nitrite), in addition to determining the intensity, speed and direction of the current. with the aid of an ADCP to obtain the flow and calculate the nutrient flow. The study area has some more remote places with little or no human influence throughout its extension, and others with untreated domestic and industrial effluent discharge points. The objective of this work is to investigate a possible anthropic contribution in the flow of dissolved inorganic nutrients from the water bodies that bathe the city of Belém-PA and surroundings. The Guamá River near the “alça viária” showed the lowest values of dissolved inorganic nutrients, unlike the Acará River which, despite its geographical distance from the RMB, showed the highest values of nutrient concentration. The mouth of the Guamá river had higher nutrient values on its right bank and the Guajará bay in its central portion, due to the influence of domestic and industrial waste. The Guamá river near the “alça viária” is relatively preserved, with a low concentration of dissolved inorganic nutrients, increasing only near its mouth, while the Acará presented higher values mainly due to the intense agricultural activity in the surroundings of its basin. The Guajará Bay, despite receiving discharges from the Acará and Guamá rivers, has lower nutrient values than the two locations, demonstrating its capacity for self-purification and dilution.