Ocean, Coastal & River Engineering Research Centre, National Research Council Canada, Ottawa, Canada; Department of Civil Engineering, University of Ottawa, Ottawa, Canada.
Mar Pollut Bull. 2022 Nov;184:114119. doi: 10.1016/j.marpolbul.2022.114119. Epub 2022 Sep 23.
Proliferation of microplastics in rivers, lakes, estuaries, coastal waters and oceans is a major global challenge and threat to the environment, livelihoods and human health. Reliable predictive tools can play an essential role in developing an improved understanding of microplastics behaviour, exposure and risk in water bodies, and facilitate identification of sources and accumulation hot spots, thereby enabling informed decision-making for targeted prevention and clean-up activities. This study presents a new numerical framework (CaMPSim-3D) for predicting microplastics fate and transport in different aquatic settings, which consists of a Lagrangian, three-dimensional (3D) particle-tracking model (PTM) coupled with an Eulerian-based hydrodynamic modeling system (TELEMAC). The 3D PTM has several innovative features that enable accurate simulation and efficient coupling with TELEMAC, which utilizes an unstructured computational mesh. The PTM is capable of considering spatio-temporally varying diffusivity, and uses an innovative algorithm to locate particles within the Eulerian mesh. Model accuracy associated with different advection schemes was verified by comparing numerical predictions to known analytical solutions for several test cases. The implications of choosing different advection schemes for modeling microplastics transport was then investigated by applying the PTM to simulate particle transport in the lower Saint John River Estuary in eastern Canada. The sensitivity of the PTM predictions to the advection scheme was investigated using six numerical schemes with different levels of complexity. Predicted particle distributions and residence times based on the fourth-order Runge-Kutta (RK4) scheme differed significantly (residence times by up to 100 %) from those computed using the traditional first-order (Euler) method. The Third Order Total Variation Diminishing (TVD3) Runge-Kutta method was found to be optimal, providing the closest results to RK4 with approximately 27 % lower computational cost.
微塑料在河流、湖泊、河口、沿海水域和海洋中的增殖是一个全球性的主要挑战，对环境、生计和人类健康构成威胁。可靠的预测工具可以在提高对水体中微塑料行为、暴露和风险的理解方面发挥重要作用，并有助于识别来源和积累热点，从而为有针对性的预防和清理活动提供决策依据。本研究提出了一种新的数值框架（CaMPSim-3D），用于预测不同水生环境中微塑料的命运和传输，该框架由拉格朗日、三维（3D）粒子跟踪模型（PTM）和基于欧拉的水动力建模系统（TELEMAC）组成。3D PTM 具有几个创新功能，使其能够准确模拟和有效地与 TELEMAC 耦合，TELEMAC 利用非结构化计算网格。PTM 能够考虑时空变化的扩散性，并使用创新算法在欧拉网格中定位颗粒。通过将数值预测与几个测试案例的已知解析解进行比较，验证了不同平流方案相关的模型精度。然后，通过将 PTM 应用于模拟加拿大东部下圣约翰河口的粒子输运，研究了选择不同平流方案对微塑料输运建模的影响。使用不同复杂程度的六种数值方案研究了 PTM 预测对平流方案的敏感性。基于四阶龙格库塔（RK4）方案的预测粒子分布和停留时间与使用传统一阶（欧拉）方法计算的结果有很大差异（停留时间相差高达 100%）。三阶全变差减（TVD3）龙格库塔方法被发现是最优的，它提供了最接近 RK4 的结果，计算成本约低 27%。
