Accumulation of floating microplastics behind the Three Gorges Dam

Area of Science:

• Environmental Science
• Ecotoxicology
• Water Quality Monitoring

Background:

• Microplastic pollution is a growing global concern, impacting aquatic ecosystems.
• The Three Gorges Reservoir (TGR) is a critical freshwater ecosystem, yet its microplastic contamination levels are poorly understood.

Purpose of the Study:

• To investigate the occurrence and distribution of microplastics in the surface water of the Three Gorges Reservoir.
• To identify the types of microplastics present and compare contamination levels with existing data.

Main Methods:

• Surface water samples were collected using trawl sampling with a 112 μm mesh net.
• Microplastic abundance was quantified per square kilometer.
• Microplastic composition was analyzed, identifying polyethylene (PE), polypropylene (PP), and polystyrene (PS).

Main Results:

• Microplastic abundances ranged from 192.5 × 10^3 to 13,617.5 × 10^3 items/km² across different areas of the TGR.
• Higher microplastic concentrations were observed in the main stream of the Yangtze River, increasing towards the Three Gorges Dam.
• Polyethylene (PE), polypropylene (PP), and polystyrene (PS) were the dominant microplastic types; coal/fly ash was also abundant.

Conclusions:

• The Three Gorges Reservoir exhibits exceptionally high microplastic pollution levels, one to three orders of magnitude greater than previously reported.
• Reservoirs may serve as significant accumulation zones, or hotspots, for microplastic pollution in freshwater systems.