Avaliação do comportamento do fósforo sob eventos de ressuspensão em sedimentos de áreas densamente urbanizadas da Baía de Guanabara - RJ, Brasil

Abstract

Guanabara Bay corresponds to the second-largest bay on the Brazilian coast, is considered one of the most densely urbanized in the world. Currently, there is an intensification of dredging activities due to the expansion of port areas. These activities trigger the resuspension of sediments, which can alter the bioavailability of nutrients in coastal aquatic ecosystems, making them susceptible to risks to the estuarine biota and human health. Thus, the general objective of this study was to evaluate the effects of sediment resuspension in the Guanabara Bay region and the possible increase in the bioavailability of phosphorus (P). Two sampling points were evaluated in the study area (Meriti and Porto do Rio), with three replicates, submitted to seven resuspension intervals (T-0, 30min, 1h, 3h, 6h, 12h, and 24h). For this, we evaluated the granulometry, phosphorus in water (P in water), total phosphorus (TP), inorganic phosphorus (IP), organic phosphorus (OP), and organic matter (OM). In Porto do Rio there was a transfer of P in the water to the sediment after resuspension, while Meriti showed an increase in the concentration of P in the water after resuspension. Only the Port of Rio exceeded what is determined by Conama Resolution 454/12 in some intervals after resuspension. Spearman's test was applied to the data, and the PT and PI in Porto do Rio showed a positive correlation r = 0.87; p< 0.05, showing that there is a relationship between the two parameters. The percentage of organic matter at both points oscillated at both points after resuspension, making it impossible to trace a trend. According to the results, it was possible to infer that the main P source in Guanabara Bay comes from the lack of sewage treatment. Despite being a eutrophic environment, Guanabara Bay showed different P remobilization dynamics in the studied areas, suggesting that mineralogy influenced the results.