Occurrence and dynamics of microplastics and emerging concern microparticles in coastal sediments: Impact of stormwater upgrade and port-associated facilities

Urban runoff is a significant source of microplastic pollution in aquatic environments, especially in coastal areas. Despite urban stormwater runoff being considered a major pathway of anthropogenic particles there's no studies about the impact of stormwater upgrades on microparticle transport. Moreover, due to the influence of anthropogenic activities, including maritime traffic and maintenance, on coastal environments, it is crucial to identify plastic debris from both inland and in-shore sources. This study evaluates characteristics, abundance, and distribution of microplastics in subtidal sediments from the southwestern Atlantic region, influenced by a recently upgraded stormwater outfall and port facilities. Herein, we have analyzed temporal trends, including seasonal dynamics and their relation with the pre- and post-upgrade of the stormwater outfall. Three main types of anthropogenic microparticles were observed: common plastic (MPs), paints (Pps), and tire wear particles (TWPs). Microparticle groups varied in morphology, color, and size distribution, including uncommon microparticle debris. Analysis by FTIR and Raman spectroscopies allows the identification of polyethylene, polypropylene, polyethylene terephthalate, polyvinyl chloride, polystyrene, polyamide, and polyacrylonitrile polymers for MPs mainly. Pigments such as Naphthol AS, phthalocyanine, and quinacridone have been identified in Pps. SEM-EDS and FTIR analysis of collected TWPs revealed similar trace metals constituents and infrared signals to those observed in tire road samples. Spatial and temporal abundances of microparticle groups were significantly different (p < 0.05), mainly related to the distance from the stormwater outfall and seasons. TWPs showed the most significant seasonal increment rate among pre and post-upgrade periods. Furthermore, the upgrades made to the stormwater system have been observed to intensify the transport and increase the presence of specific anthropogenic microparticles in subtidal sediments. Based on these findings, the occurrence of TWPs emerges as a reliable urban runoff indicator to differentiate ex and in-situ sources in multipolluted coastal environments.