Distribution, Sources, and Ecological Risk Assessment of Microplastics in the Lower Minjiang River

Area of Science:

• Environmental Science
• Ecotoxicology
• Riverine Ecosystems

Background:

• Microplastics are a pervasive global pollutant threatening freshwater ecosystems.
• Understanding microplastic contamination is crucial for assessing ecological risks.

Purpose of the Study:

• To characterize microplastic abundance, morphology, and polymer composition in the lower Minjiang River.
• To identify pollution sources and quantify ecological risks using indices like PLI, PHI, and PERI.

Main Methods:

• Microscopic observation and Raman spectroscopy for microplastic analysis.
• Integration of socioeconomic and water quality data to determine pollution sources.
• Application of Pollution Load Index (PLI), Polymer Chemical Toxicity Hazard Index (PHI), and Potential Ecological Risk Index (PERI).

Main Results:

• Moderate microplastic contamination in the Minjiang River, with higher loads in dry-season surface water and sediments.
• Predominance of transparent fibrous/fragmentary microplastics (<500 μm), primarily composed of Polypropylene (PP) and Polyethylene (PE).
• Urbanization-driven wastewater discharge identified as the main pollution source; elevated ecological risks indicated by PHI and PERI.

Conclusions:

• The lower Minjiang River shows moderate microplastic contamination but elevated ecological risks, particularly from toxic polymers.
• Sediments act as significant sinks for microplastics, with distinct contamination gradients between water and sediment.
• Effective management strategies targeting urban wastewater are essential to mitigate microplastic pollution and ecological harm.