Uptake and ecotoxicity of microplastics of different particle sizes in crop species

Microplastics (MPs) pollution threatens aquatic and terrestrial ecosystems. Herein, we assessed the uptake of MPs in seedling roots of three crop species exposed to small (0.2 μm) and large (1.0 μm) polystyrene (PS) beads by a microcosm study. Additionally, the physiological ecology of three species was also investigated after 7 d of exposure to different PS bead sizes. The results showed that fresh weight and growth inhibition was unaffected by particle sizes, while root length, shoot mass and root mass inhibition was significantly higher in C. sativus than that in P. vulgaris and S. bicolor (mean 28.6, 5.5 and 2.8 in C. sativus, P. vulgaris and S. bicolor, respectively). Uptake and accumulation were higher for small PS beads in P. vulgaris and C. sativus compared to that in S. bicolor, while more large PS beads were accumulated in C. sativus. Fluorescence intensity values of PS beads accumulation in different tissues confirmed these results. Malondialdehyde levels in seedling leaves of P. vulgaris and C. sativus were elevated in PS treatment groups but unchanged in S. bicolor. The highest and lowest proline content were observed for 0.2 μm and control groups, respectively. The Catalase activity was decreased in S. bicolor and C. sativus for large beads, with the average values of 17.5 and 20.3 Ug FW, respectively. In conclusion, different PS bead sizes significantly affected the accumulation and distribution in all species, as well as the antioxidant response. A better understanding the difference in MPs uptake and ecotoxicity between different species will help ensure food safety and effective agricultural environmental management.