Microplastics and Nanoplastics in Aquatic Environments: Aggregation, Deposition, and Enhanced Contaminant Transport

TLDR

Plastic litter is a global environmental threat, with macro‑to‑micro‑to‑nano degradation producing particles below 100 nm that are hard to detect and can be transported across air, soil, and water, yet the loads, transformations, transport, and fate of plastics in terrestrial and subsurface environments remain largely overlooked. This review estimates plastic loads across environmental compartments, critically examines nanoplastic and microplastic aggregation, deposition, and contaminant cotransport, and identifies knowledge gaps to improve risk prediction. The authors compile estimated plastic loads, review literature on aggregation, deposition, and contaminant cotransport, and analyze sorption factors, noting polyethylene’s higher capacity than other plastics. Key factors influencing subsurface aggregation and deposition are identified, polyethylene shows higher contaminant sorption than other plastics, and critical knowledge gaps are highlighted to improve risk prediction.

Abstract

Plastic litter is widely acknowledged as a global environmental threat, and poor management and disposal lead to increasing levels in the environment. Of recent concern is the degradation of plastics from macro- to micro- and even to nanosized particles smaller than 100 nm in size. At the nanoscale, plastics are difficult to detect and can be transported in air, soil, and water compartments. While the impact of plastic debris on marine and fresh waters and organisms has been studied, the loads, transformations, transport, and fate of plastics in terrestrial and subsurface environments are largely overlooked. In this Critical Review, we first present estimated loads of plastics in different environmental compartments. We also provide a critical review of the current knowledge vis-à-vis nanoplastic (NP) and microplastic (MP) aggregation, deposition, and contaminant cotransport in the environment. Important factors that affect aggregation and deposition in natural subsurface environments are identified and critically analyzed. Factors affecting contaminant sorption onto plastic debris are discussed, and we show how polyethylene generally exhibits a greater sorption capacity than other plastic types. Finally, we highlight key knowledge gaps that need to be addressed to improve our ability to predict the risks associated with these ubiquitous contaminants in the environment by understanding their mobility, aggregation behavior and their potential to enhance the transport of other pollutants.