Ehime University, 3 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan.
Ehime University, 3 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan.
Mar Pollut Bull. 2020 Nov;160:111548. doi: 10.1016/j.marpolbul.2020.111548. Epub 2020 Aug 15.
A model is proposed for the beach process of buoyant marine plastics, specifically its beaching and backwashing, by introducing beaching and backwashing diffusion coefficients and the onshore-offshore advection-diffusion equations of plastics for the upper layers in the beach and adjacent coastal sea. The backwashing diffusion coefficient was estimated from the average residence time of the beached plastics and the beach width, and then the beaching diffusion coefficient was estimated from the flux-balance assumption between the beaching and backwashing fluxes. Finite difference calculations in the staggered-grid system demonstrated that the amount of beached plastics responds as predicted by the linear system analysis when the beach had an exponential decay type of unit impulse response regardless of the ratio between the residence time and the period of beaching flux fluctuation from the nearshore. The condition in which the flux balance assumption holds was also discussed.
提出了一个用于浮质海洋塑料海滩过程的模型，特别是其冲滩和回冲过程，通过引入冲滩和回冲扩散系数以及海滩和相邻近岸海域上层的海洋塑料的沿岸-离岸输运-扩散方程。回冲扩散系数是根据冲滩塑料的平均停留时间和海滩宽度来估算的，然后根据冲滩和回冲通量之间的通量平衡假设来估算冲滩扩散系数。交错网格系统的有限差分计算表明，当海滩具有指数衰减类型的单位脉冲响应时，无论近岸冲滩通量波动的停留时间与周期之比如何，冲滩塑料的数量都会按照线性系统分析的预测进行响应。还讨论了通量平衡假设成立的条件。
