Collaborative Research: Surface Properties and Transport of Micro- and Nanoplastics in Unsaturated Soil

陆地生态系统的塑料污染是对土壤健康的新威胁。虽然人们对海洋生态系统中的塑料污染知之甚少，但对微塑料和纳米塑料在陆地系统中的去向和运输却知之甚少。微塑料和纳米塑料可能会滞留在土壤中，从而对土壤生物产生负面影响，或者它们可能会在土壤中移动，可能会污染地下水和饮用水资源。该项目旨在描述微塑料和纳米塑料在陆地系统中的命运，以便能够评估微塑料和纳米塑料造成的环境危害。随着时间的推移，将跟踪土壤中的塑料颗粒，以确定它们的化学性质是否发生变化以及它们是如何移动的。将使用四种常用的塑料：聚乙烯、聚丙烯、聚苯乙烯和一种典型的可生物降解塑料。塑料将通过暴露在紫外线和降雨中而受到环境风化的影响。然后，对微米和纳米塑料的大小、形状、表面和胶体特性进行彻底的表征。预计经过风化的微米和纳米级塑料颗粒将形成一层生态日冕，即胞外物质、土壤有机质和粘土矿物的覆盖层，使颗粒在土壤中更具亲水性和移动性。将对塑料的表面和胶体特性进行表征。此外，将对塑料在土壤和地下水中的运移进行量化，以确定微塑料和纳米塑料是否滞留在土壤或含水层中。该项目的具体目标是(1)了解风化过程中二次微塑料和纳米塑料的生成，(2)确定风化对微塑料和纳米塑料表面和胶体性质的作用，以及(3)确定微塑料和纳米塑料在非饱和多孔介质和土壤中传输的基本机制。该项目将提供有关微塑料和纳米塑料在饱和和非饱和流动条件下的流动性的机械信息。该项目还将为政策制定者提供有关可生物降解塑料在陆地环境中降解的宝贵信息。可生物降解塑料是传统塑料的一种很有前途的替代品，特别是对于一次性使用的应用。这一结果将有助于为使用可生物降解塑料的立法提供参考。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Plastic pollution of terrestrial ecosystems is an emerging threat to soil health. While there is much known about plastics pollution in marine ecosystems, little is known about fate and transport of micro- and nanoplastics in terrestrial systems. Micro- and nanoplastics may be held up in soil, thereby negatively impacting soil organisms, or they may move through soil, potentially contaminating groundwater and drinking water resources. This project aims to characterize the fate of micro- and nanoplastics in terrestrial systems, so that the environmental hazards posed by micro- and nanoplastics can be assessed. Plastic particles in soil will be tracked over time to determine whether their chemical properties change and how they move.Four commonly used plastics will be used: polyethylene, polypropylene, polystyrene, and a typical biodegradable plastic. The plastics will be subjected to environmental weathering by exposing them to UV and rainfall. Micro- and nanoplastics will then be thoroughly characterized for size, shape, and surface and colloidal properties. It is expected that the weathered micro- and nanoscale plastics particles form an "eco-corona", i.e., a covering with extracellular substances, soil organic matter, and clay minerals, which makes the particles more hydrophilic and mobile in soils. Surface and colloidal properties of the plastics will be characterized. Further, transport of the plastics in soils and groundwater will be quantified to determine whether micro- and nanoplastics are held up in soils or aquifers. The specific objectives of this project are to (1) understand the creation of secondary micro- and nanoplastics during weathering, (2) determine the role of weathering on the surface and colloidal properties of micro- and nanoplastics, and (3) identify the fundamental mechanisms involved in transport of micro- and nanoplastics in unsaturated porous media and soils. The project will provide mechanistic information on mobility of micro- and nanoplastics under saturated and unsaturated flow conditions. The project will also provide valuable information for policy makers on the degradation of biodegradable plastics in terrestrial environments. Biodegradable plastics are a promising alternative to conventional plastics, particularly for single-use applications. The results will help inform legislation on the use of biodegradable plastics.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.