Detection of small microplastics in the surface freshwater samples of Yangcheng Lake, China

Microplastics up to 20 μm are recognized as having the highest potential to cause significant impacts on aquatic environments. Current methods face challenges in detecting and chemically characterizing small microplastics in freshwater systems. In this study, using an optical confocal micro-Raman tweezer technique, the composition of particles trapped in lake aggregates collected from surface water around Yangcheng Lake in Suzhou, China, has been identified. Surface freshwater samples were analyzed from 15 different sites around the lake. In total, 514 particles were analyzed of which 136 were small microplastics. Chemical characterization showed the presence of five different polymer types, with polystyrene being the most dominant, accounting for 63% of the detected particles. Small plastics in the range of 1.1 to 8.5 μm were detected around crab restaurants and residential villages. The smallest microplastics identified were 1.1 μm polystyrene. Fragment was the most common shape of microplastics, followed by fiber and quasisphere within the volume of sample analyzed. The results suggest that the primary sources of small microplastic contamination in Yangcheng Lake may include fishing activities, agriculture, and tourism. Study findings may be used as a reference to extend the understanding of the small microplastic contamination level in inland freshwater systems. •Small microplastics have been detected in the Yangcheng Lake, China.•A method based on Raman spectroscopy and optical tweezers has been used.•Five types of polymers (PS, PE, PVC, NY6, PMMA) have been detected.•Fragments are the dominant shape.•Microplastic contamination in Yangcheng Lake may be caused by human activities.