Integrated environmental assessment of plastic pollution in the São Francisco River estuary, Brazil

Plastic pollution has emerged as a major environmental concern due to its persistence, fragmentation, and capacity to release chemical additives into aquatic systems. Estuaries are particularly vulnerable, functioning simultaneously as accumulation zones and transfer pathways for plastic debris and associated contaminants. This study provides a combined assessment of macroplastics, microplastics, and plasticizers (bisphenol A - BPA and dibutyl phthalate - DBP) in the São Francisco River estuary, northeastern Brazil. Surface water and sandy sediment samples were collected at four sites, including urban areas and locations near Conservation Units. Plastic debris was quantified and characterized, while BPA and DBP were determined as chemical markers of plastic pollution. BPA was detected in 100% of water samples and DBP in 67%, with the highest concentrations recorded in the urbanized site of Propriá (BPA: 0.72 mg · L⁻¹; DBP: 2.27 mg · L⁻¹). The highest quantities of microplastics in the water were recorded in Santana de São Francisco (0.49 items/m³) and in the sandy sediment in Pacatuba (22,80 items/m²), with a predominance of white fragments. Macroplastics showed a progressive increase in Pacatuba, totaling 2457 g. The results highlight urban influence and the estuary's role as a retention and transfer zone for plastic pollutants. The study employed multiple methodologies to analyze plastic pollution across scales, providing novel data for environmental monitoring in estuaries and Conservation Units. Findings reinforce the need for policies to reduce plastic use, improve sanitation, and promote environmental education, contributing to Sustainable Development Goals 6, 12, and 14.