Seasonal variations in the abundance and distribution of small-sized microplastics in Hong Kong's marine waters

Small-sized microplastics (20–300 μm) in Hong Kong's marine waters were examined using a bulk sampling method. The concentrations of small-sized microplastics varied from 20 to 1265 particles/m³, with an average of 362 ± 294 particles/m³, and these levels are remarkably higher than those of larger microplastics (300–5000 μm) collected by Manta trawling but remain relatively low compared to global reports. The study found higher microplastic abundance during the wet season, although seasonal differences were not statistically significant due to limited data and high sample variability. Notably, the abundance showed weak correlation with rainfall, indicating that local runoff may not be a major factor. Fibers of polyethylene terephthalate were the predominant microplastics, possibly originating from machine-washed apparel, tumble dryers, wear and tear of outdoor textiles, and fabric debris disintegration. However, the precise contribution and their geographical origins remain unclear, underscoring the need for further investigation into the transport pathways and behavior of these particles in the environment.