Nanoplastic Particle Mobility in Agricultural Soils: A Risk for Groundwater Contamination Amplified by Changing Rainfall Patterns

Agricultural soils are major sinks for plastic materials, which tend to fragment into smaller particles including nanoplastic particles (NPs <100 nm). However, the mobility of NPs in agricultural soils remains largely unknown. Here, we determined the transport of NPs with a size of 92 nm in agricultural soils under in situ conditions by using an innovative NP gold-core tracer method and an advanced lysimeter setup. We revealed that NPs can migrate through agricultural soils, potentially acting as long-term contamination sources for underlying groundwater systems. Somewhat counterintuitively, the NP mobility was higher in fine-grained clayey soils compared to coarse-grained sandy agricultural soils, suggesting that the smaller air–water interface in clayey soils reduces NP retention. Additionally, simulated extreme rainfall events, increasingly expected under climate change, showed an enhanced NP mobility, indicating that NPs become more mobile in the future in agricultural soils. Overall, these novel findings highlight the importance of considering NP mobility in agricultural soils when assessing global groundwater contamination risks, especially in clayey soils and under changing climate conditions with intensified rainfall.