Advancing Numerical Model for Fate and Transport of Microplastics in the Marine Environment

大量和持续的塑料释放到环境中，导致它们在包括加拿大北极在内的所有主要海洋栖息地积累。由于其对海洋生物群、生态系统和人类健康的潜在风险，微塑料污染已成为科学家、政府甚至非专业人士关注的主要问题。数值模型是塑料管理的重要工具，可以用来追踪塑料的起源、预测塑料的运动轨迹、识别塑料的风险热点。由于分辨率低，缺乏全面的风化过程，现有的MPs在海洋环境中的命运/运输模型仍然非常有限。溢油模型方法已被证明在跟踪浮油方面非常有用，这使得它成为一个很好的候选者，用于跟踪MPs和模拟它们的风化过程。我之前的NSERC发现基金集中于开发加拿大水域的溢油模型，这为扩展我的研究项目奠定了重要的基础，使我的研究项目在推进数值模型方面包括新兴的污染物，如MPs。具体目标是：1)开发高分辨率的水动力/冰模型，为后续的命运/运输模型提供当前和冰原；2)更好地理解不同形状的MPs的沉降行为，以支持命运/运输模型方程的发展；3)开发3D MP命运/运输模型（开放水域），考虑各种风化过程，如聚集、降解、生物污染和沉降；4)继续发展冰雪覆盖条件下的命运/运输模型；5)通过危害与暴露的比较，开展多磺酸盐对海洋生物群的风险评估。这项研究涵盖了基础研究（研究MPs的沉降行为）和应用研究（开发数值工具和风险评估）。这些创新包括：1)对不规则形状MP颗粒的复杂沉降行为产生了新的认识；2)利用非结构化网格模型模拟北极环境MPs路径，产生更好的水动力/冰强迫；3)综合风化模型的实现显著增强了现有的简单粒子跟踪模型；4)提供加拿大海域海洋生物高风险区域的新信息，如乔治亚海峡和加拿大北极群岛。该研究项目最重要的成果是：1)先进的数值模型的可用性，帮助我们了解MPs在海洋环境中的分布；2)有能力量化暴露于MPs对海洋生物的风险；3)是否有技术支持海洋塑料管理政策的制定。这些模型的应用对保护海洋生物具有环境效益，也可以为加拿大带来经济效益。

The intense and continuous release of plastics into the environment has caused their accumulation in all major marine habitats including Canadian Arctic. Because of their potential risks to marine biota, ecosystem, and human health, the microplastic (MP) pollution has become a major concern for scientists, governments, and even lay person. Numerical model is a key tool for plastic management which can be used to track their origin, predict their trajectory, and identify hotspot of risks. The existing models for fate/transport of MPs in the marine environment are still very limited due to their low resolution and lack of comprehensive weathering processes. Oil-spill model methodology has been proved to be very useful in tracking oil slicks which makes it a good candidate for adapting them for the purpose of tracking MPs and simulating their weathering processes. My previous NSERC Discovery Grant has focused on developing oil spill models for Canadian waters, which has established the important foundation for expanding my research program in advancing numerical model to include emerging contaminants, such as MPs.    The specific objectives are to: 1) developing high-resolution hydrodynamic/ice models to provide the current and ice fields for subsequent fate/transport modelling; 2) better understanding of the settling behaviours of MPs of various shapes to support the development of equations for fate/transport modelling; 3) developing 3D MP fate/transport model (open water condition) that considers various weathering processes such as aggregation, degradation, biofouling, and settling; 4) continue developing the fate/transport model for ice covered conditions; and 5) conducting risk assessment of MPs to marine biota by comparing the hazard with the exposure. This research covers both fundamental research (studying settling behaviours of MPs) and applied research (development of numerical tools & risk assessment). The novelties include: 1) generating new knowledge on the complex settling behaviours of irregular shaped MP particles; 2) producing better hydrodynamic/ice forcing using unstructured grid model for simulation of pathways of MPs in Arctic environment; 3) significant enhancement of existing simple particle tracking models by implementation of comprehensive weathering model; 4) providing new information on high risk areas for marine organism in Canadian waters such as Strait of Georgia and Canadian Arctic Archipelago. The most significant outcomes of this research program are: 1) availability of an advanced numerical model to help us understanding the distribution of MPs in the marine environment; 2) having the ability to quantify risks to marine organisms from exposure to MPs; 3) availability of a technology to support development of policy on management of marine plastics. Application of these models can have environmental benefits to protect marine organisms, and this could also bring economic benefits to Canada.