Biotrophic interactions between plant and endophytic bacteria in removal of PAHs and Cd from contaminated soils enhanced by graphene oxide

Abstract

Graphene oxide (GO)-mediated phytoremediation is a novel strategy for abating polycyclic aromatic hydrocarbons (PAHs) from contaminated soils, but the underlying mechanism has not been fully investigated. In this study, Fire Phoenix plants were grown in soils contaminated by 105.00 mg kg−1 or 154.55 mg kg−1 PAHs, containing 15 mg kg−1 Cd and 0.0, 0.3, 0.4, or 0.5 g kg−1 GO, respectively. After 150 days of plant growth, PAH removal rates from low-PAHs/Cd and high-PAHs/Cd soils amended with 0.4 g kg−1 GO were 78.95% and 73.21%, respectively. GO particularly promoted the biodegradation of high-ring PAHs as the removal rate increased by 55.69% on day 120 of plant growth. Dioxygenase genes including nidA and pdoA2 directly degraded PAHs in GO-induced remediation. GO mediated both upstream and downstream degradation pathways of PAHs, during which the tricarboxylic acid cycle initially dominated the downstream pathway followed by carbohydrate and amino acid metabolisms. Soil Cd was also significantly reduced by GO-enhanced root absorption. This study for the first time elucidated the mechanisms underpinning the interaction of Fire Phoenix plants with microorganisms in remediation of soil PAHs and Cd and illustrated the viability of GO-mediated bioremediation of PAHs and Cd from co-contaminated soils.