Microplastics in Persian Gulf offshore sediments: Distribution, polymer composition, and ecological risk assessment

This study assesses microplastics (MPs) pollution and ecological risk in offshore sediments of the Persian Gulf, a strategic semi-enclosed sea with limited offshore MPs data. To address this gap, we integrate the pollution load index (PLI), polymer hazard index (PHI), and potential ecological risk index (PERI), using Raman-validated polymer identification to link MPs abundance to polymer-specific hazardousness. Sediments from 39 stations contained 5-45 particles kg^-1, indicating broad anthropogenic influence rather than localized sources. Black fibers dominated, and polyethylene terephthalate (PET) was the most frequent polymer. However, high-hazard polymers (polyvinyl chloride and polystyrene) primarily drove risk, decoupling ecological risk from particle abundance. Although most stations had low PLI values, T1S3, in the northwestern Persian Gulf, was consistently identified as a critical risk zone by PHI and PERI because of hazardous-polymer accumulation. These findings show that polymer-level toxicity is a more sensitive indicator of offshore ecological risk than abundance alone.