Department of Civil and Environmental Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada.
The Institute of Municipal Engineering, Zhejiang University, Hangzhou 310058, China.
Mar Pollut Bull. 2024 May;202:116296. doi: 10.1016/j.marpolbul.2024.116296. Epub 2024 Apr 4.
The settling of microplastics (MPs) in the initial acceleration fall stage, i.e., before reaching the terminal settling velocity, has not been investigated, which is however important for understanding MP transport and fate. MP disks sized 3-5 mm, of three shapes and made of three polymers (1.038-1.343 g/cm) were examined. Five release ways and three release angles (0°, 45°, 90°) were used. MP disks with the release angle of 0° start to zigzag immediately after the release, while the MP disks with the release angles of 45° and 90° first adjust to a horizontal position and then zigzag. The adjustment distances in the vertical and horizontal directions, as well as the maximum vertical settling velocity, are influenced by MP density, size, release angle and release way. The detailed settling trajectory and velocity were also analyzed. Finally, the time-changing drag coefficient of MP disks was examined and discussed.
微塑料（MPs）在初始加速下降阶段（即在达到最终沉降速度之前）的沉降情况尚未得到研究，但这对于理解 MPs 的迁移和归宿至关重要。本研究选用三种形状和三种聚合物（1.038-1.343 g/cm）制成的 3-5mm 大小的 MP 圆盘作为研究对象，使用五种释放方式和三个释放角度（0°、45°和 90°）进行了实验。释放角度为 0°的 MP 圆盘在释放后立即开始曲折运动，而释放角度为 45°和 90°的 MP 圆盘则先调整到水平位置，然后再发生曲折运动。MP 密度、尺寸、释放角度和释放方式会影响垂直和水平方向的调整距离以及最大垂直沉降速度。此外，还对详细的沉降轨迹和速度进行了分析。最后，还对 MP 圆盘的时变阻力系数进行了检验和讨论。
