Spatio-temporal evaluation of macro, meso and microplastics in surface waters, bottom and beach sediments of two embayments in Niterói, RJ, Brazil

This study evaluated in the dry and rainy periods, the anthropogenic influence and the hydrodynamics in the distribution of plastic items in surface waters and bottom and beach sediments of the Jurujuba (Guanabara Bay, low and medium hydrodynamic) and Itaipu (oceanic region, high hydrodynamics) embayments; places of cultivation and extraction of mussels. Microplastics were 83% of the wastes collected, with a higher average concentration (138.41 items.kg−1) in beach sediments. High density polyethylene (HDPE) (38%), polypropylene (21%), and styrene (10%) were the most frequent polymers. There was no difference between the water and bottom sediment samples in the different embayments, in the studied periods, different from that observed in the beach sediment samples, with higher concentrations in the rainy season in Jurujuba. The results suggest that beach sediments are the best compartment to understand the dynamics of the distribution of plastic waste over time. [Display omitted] •The highest concentrations, morphological diversity and temporal variation were found in beach sediments.•The lower hydrodynamics contributed to a higher concentration of microplastics.•Microplastics corresponded to 83% of the collected waste•The prevalent type of plastic was polyethylene in both compartments.•Analyzes revealed oxidative degradation resulting from exposure to the environment.