Infiltration and Transport of PVC microplastic particles in saturated quartz sand columns

Abstract

Since microplastics are a perversive pollutant in all environmental compart-ments, posing a risk to the subsurface and entering the aquatic environment via erosion pathways, it is necessary to understand their transport behav-iours. The morphological descriptors used to characterize microplastic parti-cles are usually highly subjective. This research aims to understand and characterize microplastic movement based on their morphological descrip-tion. The infiltration and transport behaviour of 125 – 200 μm Polyvinyl chloride (PVC) plastic fragments in saturated quartz sand (1.6 – 2.0 mm) columns were investigated. Retention profiles at different ultrapure water flow rates (2.0 – 3.5 ml/min) were compared and analysed. At the beginning and end of each column test, the microplastic particles were carefully exam-ined, identified, and quantified by light microscopy. Each particle was char-acterized by dimensionless 3D morphological descriptors that can describe any particle shape. The results indicated that the transport distance of micro-plastic particles increased as their diameter decreased. PVC microplastic par-ticles, whose morphology was more 1-dimensional, were more susceptible to fragmentation within the column, promoting infiltration. Microplastic degra-dation into fragments appeared to significantly influence movement. This study offers preliminary insights into infiltration depths and morphology-dependent fragmentation of secondary microplastics in saturated coarse sand, highlighting the limitations of 2D projected images conventionally used to study the transport of microplastics.