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Significance of Hyporheic Exchange for Predicting Microplastic Fate in Rivers
Environmental Science & Technology Letters ( IF 10.9 ) Pub Date : 2020-08-20 , DOI: 10.1021/acs.estlett.0c00595
Jennifer D. Drummond 1 , Holly A. Nel 1 , Aaron I. Packman 2 , Stefan Krause 1
Affiliation  

Microplastics are abundantly found in streambed sediments, including both small and low-density particles of neutral and positive buoyancy. Although the flow of water into streambed sediments (hyporheic exchange) has previously been shown to increase the rate of delivery of fine particles to the streambed, the influence of hyporheic exchange on microplastic fate in aquatic environments has not yet been assessed in detail. Here we evaluate the effects of hyporheic exchange on microplastics by calculating and comparing the rates of delivery of microplastics to streambed sediments by hyporheic exchange and gravitational settling for combinations of particle size and density most commonly found in streams. In a field stream study, we found that 23% of all microplastic combinations have a hyporheic exchange rate that is higher than their settling rate. This fraction was as high as 42% for microplastics composed of low-density polymers, such as polyethylene. We then expand these findings to consider a wide range of hydrodynamic conditions in rivers and demonstrate that hyporheic exchange is important for the transport and fate of particles that are <100 μm in diameter, irrespective of polymer type. Models that do not include hyporheic exchange are therefore likely to substantially underestimate the deposition, retention, and long-term accumulation of microplastics in streambed sediments.

中文翻译:

换水对预测河流中微生境的意义

在流化沉积物中大量发现了微塑料,包括中性浮力和正浮力的小颗粒和低密度颗粒。尽管先前已证明水流入河床沉积物(疏水交换)会增加细颗粒向河床的输送速率,但尚未详细评估水交换对水生环境中微塑性命运的影响。在这里,我们通过流变交换和重力沉降计算和比较流中最常见的颗粒大小和密度的组合,通过计算和比较流变沉积物中微塑料的输送速率,来评估流变交换对微塑料的影响。在野外研究中,我们发现所有微塑料组合中有23%的水交换速率高于沉降速率。对于由低密度聚合物(例如聚乙烯)组成的微塑料而言,这一比例高达42%。然后,我们将这些发现扩展为考虑河流中广泛的流体动力学条件,并证明了低交换性对于直径小于100μm的颗粒的运输和结局至关重要,而与聚合物类型无关。因此,不包括低交换性交换的模型可能会大大低估了流化沉积物中微塑料的沉积,保留和长期积累。直径为100μm,与聚合物类型无关。因此,不包括低交换性交换的模型可能会大大低估了流化沉积物中微塑料的沉积,保留和长期积累。直径为100μm,与聚合物类型无关。因此,不包括低交换性交换的模型可能会大大低估了流化沉积物中微塑料的沉积,保留和长期积累。
更新日期:2020-10-13
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