Quantifying the Risk of Vegetables Absorbing High-Molecular-Weight  Pollutants:A Microscale Perspective

Abstract

The pollution of terrestrial and freshwater systems by microplastics (MPs; size < 5 mm) is causing increasing concern globally. MPs are ubiquitous in both soil and irrigation drainage, and the uptake of nanoscale MPs by plants has been demonstrated. Hence, it is crucial to determine whether MPs accumulate in edible vegetables, as this could directly threaten human health. The delineation of the upper limit of MP absorption by vegetables is greatly important for the ecological risk assessment of vegetation globally. Therefore, in this study, we evaluated MP accumulation in hydroponically grown water spinach, a widely cultivated vegetable in tropical and subtropical regions. The roots of water spinach were exposed to a mixed solution of 200 nm and 1 μm polystyrene (PS) beads for 10 days. The results showed that under the presence of submicron PS beads, micron-sized PS beads were also absorbed by the roots and transported to the leaves through the apoplastic pathway, resulting in their significant accumulation in leaves. Evidence from a short-term hydroponic cultivation experiment suggests that PS bead solutions, at high concentration, noticeably inhibit the growth of water spinach.

Keywords: Microplastics；Absorb；Transport；Accumulation；MP pollution