摘要

河流运输到海洋环境是微塑料的重要途径。然而，缺乏有关淡水系统中纳米和微塑性的命运和运输的信息。在这里，我们提出了纳米到毫米大小的球形颗粒（如微珠（100纳米-10毫米））的命运和运输情景研究，以及最先进的时空解析水文模型。该模型考虑了平流运输，同质和杂质聚集，沉降 - 再悬浮，聚合物降解，生物膜和埋藏的存在。文献数据用于参数化模型，另外通过实验确定杂聚的附着效率。对于70nm和1050nm聚苯乙烯颗粒与天然淡水中的高岭土或膨润土粘土聚集，附着效率范围为0.004至0.2。聚合物密度（1-1.5kg / L）和生物膜形成的模拟效应不大，这是因为聚合物密度的变化很大程度上被形成具有微塑性的杂聚物的过量悬浮固体所淹没。粒径对微塑性的模拟命运和保留以及沿河沉积物中积聚热点的定位具有显着影响。值得注意的是，对于约5μm的中等尺寸颗粒，保留率最低（18-25％），这意味着优先保留较小的亚微米颗粒以及较大的微米和毫米尺寸的塑料。我们的研究结果表明，河流流体动力学影响微观尺寸分布，对海洋系统的排放有深远的影响。

Riverine transport to the marine environment is an important pathway for microplastic. However, information on fate and transport of nano- and microplastic in freshwater systems is lacking. Here we present scenario studies on the fate and transport of nano-to millimetre sized spherical particles like microbeads (100 nm-10 mm) with a state of the art spatiotemporally resolved hydrological model. The model accounts for advective transport, homo- and heteroaggregation, sedimentation-resuspension, polymer degradation, presence of biofilm and burial. Literature data were used to parameterize the model and additionally the attachment efficiency for heteroaggregation was determined experimentally. The attachment efficiency ranged from 0.004 to 0.2 for 70 nm and 1050 nm polystyrene particles aggregating with kaolin or bentonite clays in natural freshwater. Modeled effects of polymer density (1-1.5 kg/L) and biofilm formation were not large, due to the fact that variations in polymer density are largely overwhelmed by excess mass of suspended solids that form heteroaggregates with microplastic. Particle size had a dramatic effect on the modeled fate and retention of microplastic and on the positioning of the accumulation hot spots in the sediment along the river. Remarkably, retention was lowest (18-25%) for intermediate sized particles of about 5 μm, which implies that the smaller submicron particles as well as larger micro- and millimetre sized plastic are preferentially retained. Our results suggest that river hydrodynamics affect microplastic size distributions with profound implications for emissions to marine systems.

https://www.ncbi.nlm.nih.gov/pubmed/27743792