ASSESSING THE TRANSPORT OF NANO-PLASTIC IN SOIL AS FUNCTION OF SIZE AND SHAPE

Abstract

Plastic pollution in agricultural soils has become an important sink for micro- and nanoplastics, raising concerns about their mobility in field conditions and the long-term risk for soil and groundwater. This thesis investigates the transport and retention of metal-doped polystyrene nanoplastics in a repacked agricultural sandy soil using mini lysimeter under controlled irrigation conditions. Three tracer-labeled nanoplastic types were used, including spherical Paladium (Pd) particles (180nm), spherical Platinum (Pt) particles (806nm), and elliptical Indium (In) particles (785nm). Zeta potential measurements revealed all particles were negatively charged, but soil effluent (EC = 251μS/cm) increased the negativity compared to rain water (EC = 37μS/cm), likely due to dissolved organic matter (DOM) enhancing colloidal stability despite higher ionic strength. The obtained result from IPC-MS shows that the spherical Pd (180nm) and Pt (806nm) particles were transported through the soil column, with recoveries of 78.51% and 55.65%, respectively. This indicates a potential risk of leaching to groundwater. Interestingly, larger Pt (806nm) particles dominated the early breakthrough, whereas smaller Pd (180nm) particles controlled the late‑time tailing. Besides, the elliptical In particles showed no measurable breakthrough, which limits the ability to compare the movement of particles of different shapes. Overall, the results show that nanoparticle mobility in sandy soil is influenced by particle size and other latent factors, which could serve as a foundation for future modeling.