[Occurrence Characteristics and Ecological Risk Assessment of Microplastics in Sewage Sludge across China]

To investigate the characteristics and ecological risk posed by microplastics （MPs） pollution in sewage sludge （SS） across China， a comprehensive analysis was conducted on 252 samples from 36 cities， employing stereomicroscopy， Fourier transform infrared spectroscopy， as well as the pollution load index （PLI）， polymer hazard index （H）， and potential ecological risk index （PERI） model. The MPs abundance in SS ranged from （2.6±0.6）×10³ to （232.6±116.1）×10³ n·kg^-1， with an average value of （35.9±40.1）×10³ n·kg^-1. The MPs abundance exhibited a descending trend of South > Southwest > East > North > Northwest > Northeast > Central China. The MPs were mainly composed of transparent fibers and shafts of 100-500 μm， with the main polymers being ethylene propylene polymer （PE-PP）， polypropylene （PP）， and polyester （PES）. Based on the total SS production in 2016， the amount of MPs emission was estimated to be 2.17×10¹⁴ particles， exhibiting a spatial distribution pattern with a greater amount in eastern China than that in western China. The landfill and land application were the primary destinations for MPs in SS（63.57%）， accounting for 1.38×10¹⁴ particles. According to the three ecological risk assessment models， the ecological risk of MPs in SS was at a high-risk level. These findings provided significant data support for the prevention and control of MPs pollution in SS across China.