Microplastic fragmentation into nanoplastics by water shear forces during wastewater treatment: Mechanical insights and theoretical analysis

⁰ NPs/mL as the water shear force increased from 32 to 100 kJ/L. Notably, the smallest NP, measuring 54.2 nm, was produced from 106 μm PS particles at 100 kJ/L. Scanning electron microscope images confirmed micro-cracks on the particle surfaces as the dominant fragmentation mechanism. A robust correlation between experimental NP sizes and theoretical predictions underscores the continuous production of NPs during water treatment processes. These results offer groundbreaking insights into the transformation of MPs within WWTPs and underscore the urgent need for effective strategies to mitigate NP pollution.