Migration dynamics of PE and PVC microplastics in soil: An experimental column-based investigation on the effects of drip irrigation

Abstract

Migration patterns of microplastics (MPs) in agricultural soil remain unclear due to a lack of scientific data. In this study, a soil column experiment was conducted using polyethylene (PE) and polyvinyl chloride (PVC) particles of different sizes under simulated drip irrigation. The MPs were collected and analysed after different irrigation time intervals (4, 8, 12, and 16 weeks) to track their migration over time.

Results showed that simulated drip irrigation triggered a time-dependent migration of MPs through soil matrices. After 16 weeks, the maximum migration depth of MP particles reached 15–20 cm. Moreover, we further revealed that the migration of MPs in sandy loam soil was influenced by both the size/type of the particles and the duration of irrigation. Comparatively, small-sized MPs, particularly those <0.5 mm, showed higher mobility compared to larger-sized MPs. A difference in mobility between the two types of MPs was also observed, with PVC exhibiting a higher mobility than PE (6.6 % of recovered PVC compared to 4 % of PE from 20 cm soil depth). This study is one of the first to simulate quantitatively and temporally (16 weeks) the migration of MPs (PE and PVC) in agricultural soil under drip irrigation. Given that MPs are hazardous materials whose transfer must be assessed, our study quantifies the critical impact of MP size and polymer type on their vertical mobility in soils, providing essential data for assessing and modelling the risks of contaminant transfer to groundwater resources.