Microplastic pollution in Pearl River networks: Characteristic, potential sources, and migration pathways

Area of Science:

• Environmental Science
• Ecotoxicology
• Water Quality Management

Background:

• Microplastic (MP) pollution poses a significant threat to aquatic ecosystems globally.
• Understanding the sources, transport, and removal of MPs in river networks is crucial but remains unclear.

Purpose of the Study:

• To investigate the spatial distribution and characteristics of microplastics in the Pearl River Basin (PRB).
• To identify the primary sources and transport pathways of MPs into river systems.
• To elucidate the mechanisms of MP removal from river water.

Main Methods:

• Field survey and water sample collection across the Pearl River Basin (> 4.5 × 10^5 km^2).
• Chemical imaging of MPs using a Laser Direct Infrared (LDIR) system.
• Statistical analysis including Partial Least Squares Structural Equation Modeling (PLS-PM).

Main Results:

• MPs detected in all samples (average 1092.86 items/L), with polyamide (PA), polyurethane (PU), and polyvinyl chloride (PVC) as dominant types.
• Population and surface runoff identified as key factors influencing MP concentrations.
• Precipitation-induced surface runoff is a major pathway for terrestrial MP transfer; river hydraulics affect MP deposition, with smooth flow (Fr <0.23) promoting removal.

Conclusions:

• This study provides critical data on MP pollution status in the PRB.
• Identified population and surface runoff as significant MP sources.
• River hydraulic dynamics play a key role in MP removal and fractionation, offering insights for water management and risk control.