Avaliação da qualidade ambiental da baía do Guajará em Belém - PA

Abstract

Water is a fundamental natural resource for the maintenance of life, so it is of the utmost importance to preserve its quality. However, with the increase of anthropic activities, it has been under severe pressure, something that can affect its quality. Thus, it is necessary to monitor the water bodies, evaluating the physical, chemical and biological factors, in order to know if such activities are causing risks to the quality of this natural resource. The objective of this work was to evaluate the environmental quality of Guajará Bay, through the analysis of water quality, sediment and benthic macroinvertebrates. The collections occur in the year 2015 and 2016, in distinct seasonal periods, rainy and less rainy, characteristic of the Amazon region. The study was performed in 4 points (PT01, PT02, PT03 and PT04). In the water analysis, the physical-chemical and microbiological parameters were evaluated; in the study of the sediment (total and leachate) was quantified the Cr, Cd, Cu and Fe metals, calculating the FC (Contamination Factor), IGeo (Geoacumulation Index) and FE (Enrichment Factor); and in the analysis of the benthic macroinvertebrates the ecological descriptors and the FAB (Bioaccumulation Factor) were evaluated. In the precipitation analysis, the precipitated volume was above the average of the normal climatological in the rainy period, and in the less rainy period it was below the average. In the chemical and microbiological analyzes of the water, the OD (dissolved oxygen) parameter was below that allowed by CONAMA Resolution nº357/05, BOD (biochemical oxygen demand) and thermotolerant coliforms above the reference limit, in addition to high concentrations of COD (chemical oxygen demand) and high CE (electrical conductivity). In the evaluation of the sediment the total sediment Cd presented values above that allowed by PEL and CONAMA nº 454/12, already in the leached phase, all the metals were within the allowed by the legislation. In general, the points presented low to moderate contamination, characterized as an unpolluted environment to a moderately polluted and enriched deficiency. In the analysis of the benthic macroinvertebrates, the most representative phylum found was the Annelida, with most of the species referring to the class Polychaeta and the subclass Oligochaeta (class Clitellata). The Oligochaetas belonging to the Tubificidae family was the most prominent. Such family is characterized as tolerant and opportunistic to situations of hypoxia, being able to inhabit in environments with eutrofizada water. The results of the ecological descriptors showed that the greatest richness, abundance, diversity and better equitability were found in the less rainy period, due to the higher concentration of nutrients and organic matter caused in this period, benthic individuals presented bioaccumulation at all points for metals Cd, Cr, Cu. The results of the matrices analyzed in the study indicated that the accumulation of pollutants in Guajará bay is due to anthropic activities, mainly by the disposal of domestic sewage without pre-treatment that is launched in this region and port activity. Thus, the importance of continuous monitoring is emphasized, given that such contamination, besides causing damages to the aquatic ecosystem, causes harm to the population, since it uses this water body for practices and recreation and fishing.