Spatiotemporal Distribution of Microplastics in the Ganjiang River (Ganzhou Section): Insight into the Source Area Impact

Abstract

The accumulation of microplastic (MP) pollution in rivers has become a global concern; however, the underlying mechanism for spatiotemporal effects on MPs remains unclear. This study investigated the Ganjiang River source area with a field survey and found relatively low MP abundances in the target rivers (3.47 ± 0.95 items/L) owing to the small background in the riverine source area. The average MP abundance in the dry season (10.9 ± 2.33 items/L) was higher than that in the middle wet season (3.47 ± 0.95 items/L), and small MPs were prone to scouring from land. Within the predominant MP shape (fiber and fragment), size (0.125–0.5 mm), and colour (polychrome and white) distribution, the contribution of functional areas was as follows: industrial > scenic > residential > natural area. MP abundances fluctuated with different rainfall levels in the wet season, while during the period when the river flow was manually regulated, a good linear relationship was observed between river flow and MP abundance, suggesting that land scouring and transportation may play a more important role than other factors. The upper river regions predominated in the group in which the average MP abundance in the dry season was higher than that in the wet season. The small watershed area in the upstream region would lead to a low terrestrial MP number, making it easy for MP content in rivers to reach a platform. This work contributes to the understanding of MP distribution in freshwater and provides a potential guideline for MP control.

Keywords: microplastic, Spatiotemporal distribution, Source area, precipitation, Urban function area