Abstract：
Mountain rivers are typically seen as relatively pristine ecosystems, supporting numerous goods (e.g., water resources) for human populations living not only in the mountain regions but also downstream from them. However recent evidence suggests that mountain river valleys in populated areas can be substantially polluted by macroplastic (plastic item >25 mm). It is unknown how distinct characteristics of mountain rivers modulate macroplastic routes through them, which makes planning effective mitigation strategies difficult. To stimulate future works on this gap, we present a conceptual model of macroplastic transport pathways through mountain river. Based on this model, we formulate four hypotheses on macroplastic input, transport and mechanical degradation in mountain rivers. Then, we propose designs of field experiments that allow each hypothesis to be tested. We hypothesize that some natural characteristics of mountain river catchments can accelerate the input of improperly disposed macroplastic waste from the slope to the river. Further, we hypothesize that specific hydromorphological characteristics of mountain rivers (e.g., high flow velocity) accelerate the downstream transport rate of macroplastic and together with the presence of shallow water and coarse bed sediments it can accelerate mechanical degradation of macroplastic in river channels, accelerating secondary microplastic production. The above suggests that mountain rivers in populated areas can act as microplastic factories, which are able to produce more microplastic from the same amount of macroplastic waste inputted into them (in comparison to lowland rivers that have a different hydromorphology). The produced risks can not only affect mountain rivers but can also be transported downstream. The challenge for the future is how to manage the hypothesized risks, especially in mountain areas particularly exposed to plastic pollution due to waste management deficiencies, high tourism pressure, poor ecological awareness of the population and lack of uniform regional and global regulations for the problem.
摘要：
山区河流通常被视为相对原始的生态系统，支持众多商品(例如，水资源），不仅生活在山区，而且生活在山区下游的人口。然而，最近的证据表明，人口稠密地区的山区河谷可能会受到大型塑料（塑料项目>25毫米）的严重污染。尚不清楚山区河流的独特特征如何调节通过它们的宏观塑料路线，这使得规划有效的缓解策略变得困难。为了刺激未来在这个差距上的工作，我们提出了通过山区河流的大塑性运输途径的概念模型。基于这个模型,我们提出了关于大塑性输入的四个假设，山区河流的运输和机械退化。然后，我们提出了田间试验的设计，允许每个假设被检验。我们假设山区河流流域的某些自然特征可以加速不当处理的大型塑料废物从斜坡到河流的输入。Further,我们假设山区河流的特定水文形态特征(例如，高流速）加速大型塑料的下游运输速率，并且与浅水和粗床沉积物的存在一起，它可以加速河道中大型塑料的机械降解，加速二次微塑料生产。以上表明，人口稠密地区的山区河流可以充当微塑料工厂，它们能够从输入到它们中的相同数量的大型塑料废物中产生更多的微塑料（与具有不同水文形态的低地河流相比）。产生的风险不仅会影响山区河流，而且还会向下游输送。未来的挑战是如何管理假设的风险，特别是在山区，由于废物管理缺陷而特别容易受到塑料污染，旅游压力大,人口的生态意识差，缺乏统一的区域和全球法规。
