Adapting Sampling Methods to River Characteristics: A Comparative Study of Microplastic Collection in Low-Flow Rivers

Microplastics, plastic particles smaller than 5 mm, are significant pollutants of growing global concern due to their persistence, widespread distribution, and potential ecological and human health risk. Numerous studies have proposed different methods for sampling microplastics in river sediments and water. However, comparative studies evaluating how different sampling methods affect the quantification of microplastic abundance in surface water remain limited. This study focused specifically on surface water, as it represents the primary pathway of microplastic transport, and the yield is most directly influenced by sampling method selection. Therefore, this study aimed to compare the abundance and characteristics of microplastics collected using three sampling methods: plankton nets, buckets, and pumps, which were selected to represent the full spectrum of commonly used riverine surface water collection approaches. Each method collected an equivalent volume of water, 1000 L. Statistical analysis showed no significant differences among the methods in terms of microplastic abundance and characteristics. These results suggest that the selection of a sampling method should be primarily based on river characteristics such as flow velocity, depth, and channel width rather than methodological differences. The findings provide practical guidance for selecting appropriate sampling approaches in low-flow river environments.