Uptake and translocation of microplastics from sewage sludge by the fern Pteris vittata.

Abstract

Microplastics (MPs) contamination represents an emerging threat to terrestrial ecosystems. A significant source of MPs is the land application of sewage sludge as a soil amendment. Once released into the environment, MPs are difficult to remove due to their small size, chemical persistence, and widespread distribution. Phytoremediation offers a sustainable strategy for in situ soil remediation, employing plants to extract, stabilize, or degrade pollutants. However, its application to MPs removal remains largely unexplored. Here, we investigated the capacity of the fern Pteris vittata to absorb MPs from soils amended with sewage sludge. We show that P. vittata is able to uptake, through the roots, MPs derived from different types of plastic polymers commonly detected in the environment, including PE, PP, PA, PU, PET, PVA, PS, EVA, PMMA and ABS. Among them, PE, PA, PP, PU, PET, PVA, EVA and PVC were translocated to the fronds. Furthermore, MPs content in roots and fronds increased with the amount of sewage sludge in the soil. Biometric index analyses show that roots and fronds growth is reduced in plants treated with increasing concentrations of sewage sludge. The expression of the oxidative stress related genes CAT, SOD, APX, and of the aquaporins NIP6.1 and PIP2.8, is repressed in roots but not in fronds, suggesting localized physiological stress induced by MPs. This study provides the first evidence that P. vittata can uptake MPs via roots and translocate them to aboveground tissues, supporting its potential use for MPs phytostabilization or phytomanagement strategies.