Spatiotemporal distribution of microplastics in the Ganzhou section of the Ganjiang river: An insight into the source area impact

Abstract

Field surveys for riverine microplastics (MP) are profoundly affected by background MPs from upstream cities, resulting in uncertainty when exploring the underlying mechanism of MP source and distribution. In this study, the Ganzhou Section of the Ganjiang River was surveyed because of its minor background effects and large anthropogenic influences. Relatively low MP abundance was found in the target rivers owing to the small background in the riverine source area. The average MP abundance in the dry season (10.9 ± 2.33 items L–1) was higher than that in the mid-wet season (3.47 ± 0.95 items L–1). The polymers were predominantly cellophane and polyethylene. The contribution of the functional areas to the predominant MP shape (fibre and fragment), size (0.125–0.5 mm), and colour (polychrome and white) distribution, was as follows: industrial > scenic > residential > natural areas. MP abundances fluctuated with different rainfall levels during the wet season, and varied synchronously with the river flow during a flow-controlled period, suggesting that land scouring and transportation played more critical roles than sediment release. The small watershed area in the upper reaches of the river caused a low terrestrial MP number, making it easy for the riverine MP content to reach a plateau. This work contributes to the understanding of MP distribution in freshwater and provides a potential guideline for MP control.