Microplastics in Santos São Vicente estuarine – Hotspot in sediments caused by low energy hydrodynamic events in strongly populated areas

Microplastics (MPs) have emerged as a significant class of contaminants due to their widespread presence in various environmental compartments. The ingestion of these particles poses a risk to both human health and the local biota. The investigation of the Santos estuary reveals the abundance of microplastics in the mangrove sediment. The highest concentration was 62,850–93,050 MPs·kg⁻¹dw, never seen before in Latin America coast. The region investigated is characterized for silting sites and low energy events, notably Rio dos Bugres, influenced by anthropic aspects, while the São Vicente e Santos channels prevail the high energy hydrodynamic regime. In consequence, the MPs are entrapped in the interior of the estuary, affecting drastically the biota of mangrove. Spectroscopic investigation identified: polymers, pigments, herbicide and additives. The hypothesis is that densely populated siltation areas combined with low-energy events serve along the estuary for MPs accumulation and hotspots formation.