• • Surface water microplastic concentrations in the Xin'an River ranged from 350 to 3700 n·m−3, with the 0–0.5 mm size fraction comprising 33.93% of total particles, indicating a dominance of small fragments that pose higher ingestion risks to aquatic organisms.
• • Sediment microplastic concentrations were 25–200 n·kg−1, with 0–0.5 mm particles accounting for 49.63%, and fibers comprising 47.08% of the total, suggesting textile-derived pollution is a major contributor to sediment contamination.
• • Polymer analysis revealed PET (36.61%) and polyamide (23.22%) as the primary materials, both commonly used in textiles and packaging, underscoring the influence of domestic and industrial discharges on microplastic composition.
• • Ecological risk assessment indicated that sites with PVC presence exhibited risk level III (risk index >100) despite low PVC abundance, highlighting the disproportionate hazard posed by high-toxicity polymers in the river system.