Current understanding of subsurface transport of micro‐ and nanoplastics in soil

Abstract

Environmental problems caused by plastic pollution in terrestrial systems have received increasing attention, especially the issues related to micro-and nanoplastics. Soils are a major receptacle and reservoir of plastics, and accumulated plastics can negatively affect soil health. In this short review, we discuss the current state of knowledge of subsurface transport of micro-and nanoplastics in soils. We discuss the fundamental transport mechanisms for micro-and nanoplastics and highlight the peculiarities of environmentally relevant micro-and nanoplastics. Plastic particles >10 μm are generally filtered out in soil, but smaller plastic particles have the potential to move through soil. Larger plastics in soil will break down into micro-and nanoplastics over time due to environmental weathering reactions, making the plastics more prone to subsurface transport. Moreover, interactions with microorganisms and dissolved organic matter may render micro-and nanoplastics more hydrophilic, thereby facilitating subsurface transport. Further, soil organisms can move plastic particles by bioturbation, and plastics themselves can affect soil hydraulic properties. Although much of the past research has focused on transport of pristine plastic particles, focus should be given to environmentally relevant plastics, considering the complexities of irregular shape, polydisperse size, and heterogenous surface properties, as well as the temporal changes of these properties caused by continuous environmental modifications. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

End-of-Life Management Options for Agricultural Mulch Films in the United States—A Review

“…Inevitably, not all mulch fragments can be completely removed, and some will remain in the field. If these fragments degrade into micro-and nano-plastics, subsurface transport through soil may be possible (Yu and Flury, 2020).…”

“…After burial in a landfill, polyethylene mulch debris, which is frequently embrittled due to exposure to sunlight during its use in the field, will undergo further degradation, producing micro-and nano-plastics that serve as vectors for release of plasticizers and other potential toxicants into the environment. Micro-and nano-plastics can be carried away by wind and water, or taken up by plants (Li et al, 2020;Yu and Flury, 2020). When this occurs, the pollutants can leak into ground and surface water sources (Steinmetz et al, 2016).…”

Nanoplastics: Status and Knowledge Gaps in the Finalization of Environmental Risk Assessments

“…Soil constitutes an important reservoir of MPs and NPs [ 123 ]. The presence of plastic fragments has been recognized as one of the most important problems related to the quality of soil in agroecosystems [ 124 ], and the calculated risk for MPs has been assessed as unacceptable to soil biota [ 29 ].…”

Interactions between water flow and microplastics in silt loam and loamy sand

“…The selected polyethylene MP particles contain nearly no hydrophilic O-functionalities that are effective in soil-water improvement (Bordoloi et al, 2018(Bordoloi et al, , 2019Xing et al , 2019Xing et al , , 2021; therefore, the strong hydrophobicity of the selected polyethylene MP particles also accelerated the flow of soil water through the pores (Ding et al, 2019;Wang et al, 2020;Yu & Flury, 2021). Low-density MPs (lower than 1.0 g cm −3 ) cannot be dissolved.…”

“…Microplastic sources are mainly divided into primary and secondary sources (Lots et al, 2017). They are mainly found in rivers, sewage sludge, wastewater from irrigation systems, landfills, film-mulching-covered cropland, marine surface water, and sediment (Horton et al, 2017;Nizzetto et al, 2016;Yu & Flury, 2021). Since the exchange of matter and energy between organisms and environment occurs in soils, the effect of MPs in soils should be determined.…”