Preston Colette A, McKenna Neuman Cheryl L, Aherne Julian
School of the Environment, Trent University, Peterborough, Ontario, K9J 0G2, Canada.
Environ Sci Technol. 2023 Aug 15;57(32):11937-11947. doi: 10.1021/acs.est.3c03671. Epub 2023 Jul 31.
Microplastics (MPs) have been found in all terrestrial, marine, and riparian environments, including remote regions. This implies that atmospheric transport is an important pathway when considering MP sources and global budgets. However, limited empirical data exist to aid in effective development and parameterization of MP atmospheric transport models. This study measured the atmospheric settling and horizontal drift velocities of various sizes and shapes of MPs in two specially designed settling columns using a laser Doppler anemometer. The settling velocities were generally lower than modeled values, while shape exerted the most significant influence on the rate of settling. Rather than conforming to well-established, power-law models, each class of MP exhibited a linear but different relationship between MP size and settling velocity, with markedly higher slopes for the spheres and cylinders as compared to the films and fibers. Shape also had a substantial influence on particle drift, with the fibers and films exhibiting the greatest horizontal motion, as suggestive of their changing orientation in response to particle interactions and fluid drag. As a consequence, microplastic particles identified within atmospheric deposition samples collected at a single point may derive from entirely different sources representing a wide range in transport distance.
微塑料（MPs）已在包括偏远地区在内的所有陆地、海洋和河岸环境中被发现。这意味着在考虑微塑料来源和全球预算时，大气传输是一条重要途径。然而，目前存在的实证数据有限，无法有效助力微塑料大气传输模型的开发和参数化。本研究使用激光多普勒风速仪，在两个专门设计的沉降柱中测量了各种尺寸和形状的微塑料的大气沉降和水平漂移速度。沉降速度通常低于模型值，而形状对沉降速率的影响最为显著。每一类微塑料并非符合已确立的幂律模型，而是在微塑料尺寸和沉降速度之间呈现出线性但不同的关系，与薄膜和纤维相比，球体和圆柱体的斜率明显更高。形状对颗粒漂移也有重大影响，纤维和薄膜表现出最大的水平移动，这表明它们会因颗粒相互作用和流体阻力而改变方向。因此，在单点采集的大气沉降样本中识别出的微塑料颗粒可能来自完全不同的来源，代表着广泛的传输距离。
