Direct field measurements of macroplastic fragmentation during its transport in rivers are currently unavailable, and there is no established method to perform them. Previous studies have showed that macroplastic fragmentation results in the production of harmful microplastics, and river channels can be hotspots for this process. Therefore, obtaining information about this process is crucial for quantifying the production of secondary microplastics in rivers and assessing the related risks for riverine biota and human health. Here, we propose a simple low-cost methodology for quantifying riverine macroplastic fragmentation by conducting repeated measurements of the mass of tagged macroplastic items before and after their transport in the river. As a proof-of-concept for this method, we conducted a 52–65 day experiment that allowed us to measure a median fragmentation rate of 0.044 ± 0.012 g for 1-liter PET bottles during their transport at low to medium flow in the middle mountain Skawa River in the Polish Carpathians. Using the obtained data (n = 42), we extrapolated that during low to medium flows, the median yearly mass loss of PET bottles in the study section is 0.26 ± 0.012 g/year (0.78 ± 0.036 % of bottle mass), and the median rate of bottle surface degradation is 3.13 ± 0.14 μm/year. These estimates suggest a relatively high fragmentation rate for a PET bottle in a mountain river even under low to medium flow conditions without high-energy transport. We discuss how our simple and relatively low-cost methodology can be flexibly adapted and future optimized to quantify macroplastic fragmentation in various types of rivers and their compartments, informing future mitigation efforts about the rates of formation and dispersion of secondary microplastics.

中文翻译：

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首次尝试测量河流中的大塑料碎片


目前还无法直接现场测量大塑料在河流中的运输过程中的破碎情况，也没有既定的方法来进行测量。先前的研究表明，大塑料破碎会导致有害微塑料的产生，而河道可能是这一过程的热点。因此，获取有关这一过程的信息对于量化河流中次生微塑料的产生以及评估河流生物群和人类健康的相关风险至关重要。在这里，我们提出了一种简单的低成本方法，通过在河流中运输之前和之后重复测量标记的大塑料物品的质量来量化河流大塑料碎片。作为该方法的概念验证，我们进行了 52-65 天的实验，测量到 1 升 PET 瓶在中低流量运输过程中的中值破碎率为 0.044 ± 0.012 g波兰喀尔巴阡山脉的斯卡瓦河山。利用获得的数据 (n = 42)，我们推断，在低至中流量期间，研究部分 PET 瓶的年质量损失中位数为 0.26 ± 0.012 克/年（瓶子质量的 0.78 ± 0.036 %），并且瓶子表面退化的中值率为 3.13 ± 0.14 μm/年。这些估计表明，即使在没有高能量传输的中低流量条件下，PET 瓶在山区河流中的破碎率也相对较高。我们讨论了如何灵活调整和未来优化我们简单且相对低成本的方法，以量化各种类型的河流及其分区中的大塑料碎片，为未来的缓解工作提供关于次生微塑料的形成和扩散速率的信息。