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”，并分解成更小的碎片，包括微塑料（MP）（100 nm-5 mm）和纳米塑料（NP）（<100 nm）。MP/NP由于其物理危害和化学毒性而对水生生物、人类健康和生态系统有害。为了评估MP/NP的环境影响，了解这些新兴污染物的命运和运输至关重要。聚集（颗粒彼此附着以形成大的聚集体）和沉积（颗粒附着于运输介质）是影响MP/NP在地下环境中的命运和运输的最重要的过程之一。预计MP/NP的性质、水化学以及运输介质的矿物和有机组成将显著影响MP/NP的聚集和沉积。然而，大多数研究仅检查了原始聚苯乙烯MP/NP，而没有检查环境中更丰富的聚乙烯或聚丙烯MP/NP。“老化”改变MP/NP（例如，形状和大小）以及这可能如何影响其环境行为在很大程度上是未知的。此外，大多数研究使用具有简单组成的人工电解质溶液作为背景溶液，并使用清洁的石英砂柱作为传输介质来研究MP/NPs的聚集和沉积。这些模型解决方案中的MP/NP行为可能不能完全代表包含多个相互作用组分的天然水。石英砂也不是天然土壤复杂成分的良好代表。我的研究计划的短期目标是通过进行实验来研究环境相关条件下MP/NPs的聚集和沉积，以填补这些知识空白。将制备、“老化”和表征具有不同性质的各种聚乙烯、聚丙烯和聚苯乙烯MP/NP。将系统地研究MP/NP在人工电解质溶液中以及在具有复杂组成的土壤溶液中的聚集。将使用填充有天然土壤或矿物混合物的柱来检查MP/NP沉积，以确定单个和多个天然组分的影响。将使用回归方法、理论计算和数学建模来分析实验结果。在与环境相关的地球化学条件下获得的关于MP/NP聚集和沉积的知识将能够更准确地预测MP/NP的环境行为，这有助于行业和政府制定适当的实践和指导方针，以应对塑料废物的负面环境影响。此外，拟议的研究将提供全面和高质量的培训，这将有助于创造一流的加拿大科学工作队伍。

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.