Micro and Nanoplastic Aggregation and Deposition in Subsurface Environments

塑料制品的广泛生产、使用和处置导致塑料废物释放到环境中。塑料通过风化过程“老化”，分解成更小的碎片，包括微塑料（MPs） （100 nm-5 mm）和纳米塑料（NPs） （<100 nm）。MPs/NPs由于其物理危害和化学毒性对水生生物、人类健康和生态系统有害。为了评估MPs/NPs的环境影响，了解这些新出现的污染物的命运和运输是必不可少的。聚集（颗粒相互附着形成大聚集体）和沉积（颗粒附着在运输介质上）是影响地下环境中MPs/NPs命运和运输的最重要过程。MPs/NPs的性质、水化学以及输送介质的矿物和有机组成预计将显著影响MPs/NPs的聚集和沉积。然而，大多数研究只检查了原始聚苯乙烯MPs/NPs，而没有检查环境中更丰富的聚乙烯或聚丙烯MPs/NPs。“老化”改变了MPs/NPs（例如，形状和大小），而这可能如何影响它们的环境行为在很大程度上是未知的。此外，大多数研究采用成分简单的人工电解质溶液作为背景溶液，以干净的石英砂柱作为输运介质来研究MPs/NPs的聚集和沉积。这些模型溶液中的MPs/NPs行为可能不能完全代表含有多种相互作用成分的天然水的行为。此外，石英砂也不能很好地代表天然土壤的复杂成分。我的研究计划的短期目标是通过开展实验研究MPs/NPs在环境相关条件下的聚集和沉积来填补这些知识空白。将制备各种具有不同性能的聚乙烯、聚丙烯和聚苯乙烯MPs/NPs，并对其进行“老化”和表征。MPs/NPs在人工电解质溶液和复杂成分的土壤溶液中的聚集将被系统地研究。MPs/NPs沉积将使用填充天然土壤或矿物混合物的柱来检查，以确定单个和多个天然成分的影响。将运用回归方法、理论计算和数学建模对实验结果进行分析。在与环境相关的地球化学条件下，对MPs/NPs聚集和沉积的了解将有助于更准确地预测MPs/NPs的环境行为，这有助于工业和政府建立适当的做法和指导方针，以应对塑料废物对环境的负面影响。此外，拟议的研究将提供全面和高质量的培训，这将有助于建立一支一流的加拿大科学队伍。

The widespread production, use, and disposal of plastic products has led to the release of plastic wastes into the environment. Plastics are "aged" by weathering processes and break down to smaller pieces including microplastics (MPs) (100 nm-5 mm) and nanoplastics (NPs) (<100 nm). MPs/NPs are harmful to aquatic organisms, human health, and ecosystems due to their physical hazards and chemical toxicity. To evaluate the environmental impacts of MPs/NPs, understanding the fate and transport of these emerging contaminants is essential. Aggregation (particles attach to each other to form large aggregate) and deposition (particles attach to transport media) are among the most important processes influencing the fate and transport of MPs/NPs in subsurface environments. The properties of MPs/NPs, water chemistry, and mineral and organic composition of transport media are expected to significantly influence MPs/NPs aggregation and deposition. Yet, most studies have examined only pristine polystyrene MPs/NPs but not the polyethylene or polypropylene MPs/NPs that are more abundant in the environment. "Aging" alters MPs/NPs (e.g., shape and size) and how this may influence their environmental behaviour is largely unknown. Moreover, most investigations use artificial electrolyte solutions with simple composition as background solution, and clean quartz sand columns as transport media to study MPs/NPs aggregation and deposition. MPs/NPs behaviour in these model solutions may not fully represent that in natural water that contains multiple interacting components. Also quartz sand is not a good proxy for the complex composition of natural soils. The short-term objective of my research program is to fill these knowledge gaps by carrying out experiments to investigate MPs/NPs aggregation and deposition under environmentally relevant conditions. A variety of polyethylene, polypropylene, and polystyrene MPs/NPs with distinct properties will be prepared, "aged", and characterized. The aggregation of the MPs/NPs in artificial electrolyte solutions, and in soil solutions with complex compositions will be systematically investigated. MPs/NPs deposition will be examined using columns packed with natural soils or mineral mixtures to determine the effect of individual and multiple natural components. Regression methods, theoretical calculation, and mathematical modeling will be used to analyze the experimental results. The knowledge gained on MPs/NPs aggregation and deposition under environmentally relevant geochemical conditions will enable more accurate prediction of the environmental behaviour of MPs/NPs, which helps industries and governments establish proper practices and guidelines for tackling the negative environmental impacts of plastic wastes. Furthermore, the proposed research will provide well-rounded and high-quality training, which will contribute to the creation of a top-notch Canadian scientific workforce.