Micro and Nanoplastic Aggregation and Deposition in Subsurface Environments

塑料产品的广泛生产、使用和处置导致了塑料废物向环境中的排放。塑料通过风化过程“老化”，并分解成更小的碎片，包括微塑料(MPS)(100 nm-5毫米)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都是有害的。要评估MPS/NPs的环境影响，了解这些新出现的污染物的去向和迁移是至关重要的。聚集(颗粒相互附着形成大团聚体)和沉积(颗粒附着在传输介质上)是影响MPS/NPs在地下环境中去向和传输的最重要过程。MPS/NPs的性质、水化学以及运输介质的矿物和有机成分预计将显著影响MPS/NPs的聚集和沉积。然而，大多数研究只研究了原始的聚苯乙烯MPS/NPs，而没有研究在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)，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，大多数研究使用组成简单的人工电解液作为背景溶液，以洁净的石英砂柱作为传输介质来研究MPS/NPS的聚集和沉积。MPS/NPs在这些模型溶液中的行为可能不能完全代表含有多种相互作用成分的天然水中的MPS/NPs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来研究MPS/NPS在环境相关条件下的聚集和沉积，以填补这些知识空白。各种不同性质的聚乙烯、聚丙烯和聚苯乙烯MPS/NPs将被制备、老化和表征。我们将系统地研究MPS/NPs在人工电解质溶液和复杂组成的土壤溶液中的聚集。将使用填满天然土壤或矿物混合物的色谱柱检查MPS/NPs的沉积，以确定单个和多种自然成分的影响。采用回归分析、理论计算和数学建模等方法对实验结果进行分析。在与环境有关的地球化学条件下MPS/NPs的聚集和沉积所获得的知识将有助于更准确地预测MPS/NPs的环境行为，从而帮助行业和政府制定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顶尖的加拿大科学劳动力队伍。

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.