Ocorrência e distribuição de microplásticos nos sedimentos de fundo, margem e nas águas superficiais do sistema lagunar Maricá-Guarapina (RJ)

Abstract

The increasing urbanization of the coast has often caused several impacts from the disposal of solid waste, domestic and industrial pollutants, culminating in the imbalance of lagoon ecosystems and harming important activities such as artisanal fishing and local tourism. The Maricá-Guarapina lagoon system, located in the municipality of Maricá (RJ), has been presenting problems related to pollution due to the occupation of its marginal areas in recent decades. Given the above, knowledge about pollution by solid waste in this environment, as well as the processes responsible for the origin and distribution of these materials, are of great relevance for the analysis of the environmental quality of these lagoons. Studies of this nature make it possible to identify the impacts caused by the activities carried out in the surroundings of this environment and the state of pollution by solid waste in the lagoon system. This study aimed to establish a diagnosis about pollution by solid waste in Lagoas de Maricá and Guarapina, using microplastics as an indicator. Field work was carried out to collect 16 samples of surface water, 16 samples of bottom sediments and 13 of the lagoon margin, for the extraction and classification of microplastics. Laboratory procedures include weighing the dry samples, sieving, extracting microplastics using the density separation method and identifying the microplastics found with the aid of a binocular magnifying glass. The results allowed identifying the presence of 5,339 microplastics in the studied lagoons, with the highest concentrations in the lagoon margin (40.4%), followed by the water surface (39%) and in the bottom sediments (20.60%). This value represents an average of 165.92 MPs/kg–1 for margin sediments, 68.75 MPs/kg–1 for bottom sediments and 11.93 MPs/m–3 for surface water. The types of microplastics identified were: fragments (36.09%), fibers (29.96%), films (26.72%), pellets (4.46%), foams (2.29%) and styrofoam (0 .48%). A total of 98.89% of the analyzed microplastics appeared to have a worn surface, indicating friction or deterioration by the action of weathering processes. Among the colors, blue predominated for fragments (34.22%), fibers (26.83%) and films (52.52%), bronze for pellets (29.41%), and white for foams (36.07%). and polystyrenes (96.43%). The possible sources of microplastics for the Maricá-Guarapina lagoon system may be related to the process of urban expansion, leisure and tourism activities, with a significant contribution from rivers, urban surface runoff and the sea. As it is a confined type lagoon with low exchange with the sea, the time of permanence of materials in availability on the water surface is longer in the lagoon of Maricá. In Guarapina, the Ponta Negra Canal allows the constant exchange of water between the lagoon and the sea, which also favors the remobilization of microplastics out of this environment. On the other hand, the entry of water through the channel allows the entry of microplastics into the lagoon, especially during storm events, as observed in this study.