Microplastics and nanoplastics barely enhance contaminant mobility in agricultural soils

Abstract

Farmland soils are prone to contamination with micro- and nanoplastics through a variety of agricultural practices. Concerns are recurrently raised that micro- and nanoplastics act as vector for organic contaminants to deeper soil layers and endanger groundwater resources. Whether and to what extent micro- and nanoplastics facilitate the transport of organic contaminants in soil remains unclear. Here we calculated the ratio between transport and desorption time scales using two diffusion models for micro- and nanoplastics between 100 nm and 1 mm. To identify micro- and nanoplastics bound contaminant transport we evaluated diffusion and partitioning coefficients of prominent agrochemicals and additives and of frequently used polymers e.g., polyethylene and tire material. Our findings suggest that the desorption of most organic contaminants is too fast for micro- and nanoplastics to act as transport facilitators in soil. Contaminant transport enabled by microplastics was found to be relevant only for very hydrophobic contaminants (logKow >5) under preferential flow conditions. While micro- and nanoplastics might be a source of potentially harmful contaminants in farmland soils this study suggests that they do not considerably enhance contaminant mobility.

Atmospheric micro (nano) plastics: future growing concerns for human health

“…A study by Hüffer et al ( 2018 ) found that the polymer surface of PS micro (nano) plastics could become oxidized over time in the environment, making them more likely to interact with living things or adsorb organic contaminants. Castan et al ( 2021 ) evaluated the partitioning and diffusion coefficients for PE and tire-wear micro (nano) plastics bound contaminant migration (agrochemicals or pesticides such as hexachlorobenzene, endrin, aldrin, dichlorodiphenyltrichloroethane, transnonachlor, and additives such as polychlorinated biphenyls) in soil, and found rapid desorption. They were skeptical about micro (nano) plastics’ ability to assist pollutant migration or mobility.…”

Greenhouse farming as a source of macroplastic and microplastics contamination in agricultural soils: a case study from Southeast-Hungary

“…Furthermore, the quality of agricultural products and the growth and photosynthesis of plants are altered by the presence of microplastics (YANG et al, 2021). Importantly, microplastics can adsorb and transport contaminants such as heavy metals and other pollutants in the soil environment (CASTAN et al, 2021,). Lastly, direct ingestion of microplastics or consumption through contaminated food, such as fish and agricultural products, is a threat to human health (MO et al, 2021).…”

Plants oxidative response to nanoplastic

“…under the influence of sunlight, temperature, humidity and wind, which account for 70-80% of all plastic released into the environment ( Lambert and Wagner, 2016 ; Kiran et al., 2022 ). Most plastic pollution comes from anthropogenic activities, such as tire wear run off from roads, packaging, building materials, fishing gears, automotive parts, electronic utilities and agro-industry components ( Geyer et al., 2017 ; Horton et al., 2017 ; Pinto Da Costa et al., 2020 ; Kiran et al., 2022 ; Law and Narayan, 2022 ; Castan et al., 2021 ; Huang et al., 2022 ), as well as from atmospheric transport (e.g. wind drift) ( Figure 3 ).…”