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

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.