Guangdong Provincial Key Laboratory of Water Quality Improvement and Ecological Restoration for Watershed, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou 510006, China; Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 511458, China.
College of Environmental Science and Engineering, Guilin University of Technology, Guilin 541004, China.
Environ Int. 2023 Nov;181:108265. doi: 10.1016/j.envint.2023.108265. Epub 2023 Oct 17.
In rivers, riverbeds are considered to have dual properties as a short-term sink and a source of further mobilization for microplastics. To better understand the sources, storage, and fate of microplastics in river systems, this study quantified the formation of microplastic hotspots in riverbeds and seasonal variations in microplastic inventories in riverbeds, especially for small-sized microplastics (<330 µm), with a fluorescence-based protocol. This study provides first-hand measured evidence for the sequestration of microplastics in the riverbed under low-flow conditions and its export from the riverbed under high-flow conditions. The results show that riverbeds in urban areas are still hotspots for microplastic pollution and that high inputs of urban microplastics control microplastic load in its downstream areas. Seasonal rainfall exported 34.86 % (equivalent to 4.34 × 10 items/8.57 t) of microplastic pollution from the riverbed, and its removal capacity may be related to the rainfall intensity. Wider riverbeds are conducive to the formation of microplastic hotspots due to the flow slow down. Most importantly, rainfall-driven scouring of the riverbed can enhance the pollution of small-sized microplastics in the riverbed, especially the smallest-size microplastics (<100 µm). Therefore, this study not only contributes reliable information about the sequestration and export of microplastics in the riverbed, but also provides a possible mechanism to explain the lack of small-sized microplastics (<330 µm) in the ocean.
在河流中，河床被认为具有双重特性，既是微塑料的短期汇，也是进一步迁移的源。为了更好地了解河流系统中微塑料的来源、储存和命运，本研究通过荧光基方案定量量化了河床中微塑料热点的形成和河床中微塑料储量的季节性变化，特别是对于小尺寸微塑料（<330μm）。本研究提供了河流低流量条件下微塑料在河床中被隔离以及高流量条件下从河床中输出的第一手实测证据。结果表明，城市地区的河床仍然是微塑料污染的热点，城市微塑料的大量输入控制了其下游地区的微塑料负荷。季节性降雨将 34.86%（相当于 4.34×10 items/8.57 t）的微塑料污染从河床中输出，其去除能力可能与降雨强度有关。较宽的河床由于水流减缓，有利于形成微塑料热点。最重要的是，河床的降雨冲刷可以增强河床中小尺寸微塑料（<100μm）的污染。因此，本研究不仅提供了有关河床中微塑料隔离和输出的可靠信息，还提供了一种可能的机制来解释海洋中缺乏小尺寸微塑料（<330μm）的现象。
