The revelry of plastic! Quali-quantitative variation of microplastics in freshwater before and after Carnival in south-eastern Brazil

Context Pollution by synthetic polymers is even more problematic to the environment when this material is fragmented into small portions, forming microplastics (MPs). Aims We analysed the influence of the Brazilian Carnival on the abundance and richness of MPs in the Paraíba do Sul River (PSR). Specific objectives included classifying MPs by shape, colour and polymer, and quantifying and comparing the abundance and richness of surface-water MPs before, during and after Carnival. Methods Samples were taken from the superficial layer of the water column in 2023, by using manta net. Key results In total, 843 MPs were identified in the surface water of PSR. Higher MP concentrations were observed after the Carnival event than in the other two periods. Blue and black fibres were the predominant MPs. Glitter and sequin occurred only during the Carnival and post-Carnival periods. Polyester, polyamide and polyethylene were the most abundant in all the periods. Conclusions Our findings strongly indicated that Carnival represents a potential short-term source of MP introduction into the PSR basin. Implications A significant 170% increase in MP abundance was observed 10 days after the Carnival, which is an event occurring across multiple locations in the PSR basin.