Ryegrass (Lolium multiflorum L.) and Indian mustard (Brassica juncea L.) intercropping can improve the phytoremediation of antibiotics and antibiotic resistance genes but not heavy metals

Lolium multiflorum and Brassica juncea display phytoremediation potential for heavy metals and antibiotics pollution. However, there is limited understanding of their function in removing combined pollutants (heavy metals, antibiotics and antibiotic resistance genes (ARGs)) under different cropping patterns. Sole cropping had little effect on heavy metals, but reduced antibiotics by 2.46%–84.88% and increased ARGs by 15.96%–33.82%. Intercropping was more beneficial to soil remediation and plant accumulation of L. multiflorum, and further increased the remediation of antibiotics by 2.38%–54.40%. Members of phyla (Actinobacteria, Bacteroidetes, and Proteobacteria) were mainly responsible for most antibiotics removal. Compared with sole cropping, intercropping reduced more ARGs abundance in rhizosphere soil for L. multiflorum (20.43%) and in bulk soil for B. juncea (23.22%). Mobile genetic elements (MGEs) played a significant role in the variation of ARGs. Further, sample type showed a higher indirect negative impact on ARGs by mainly affecting soil properties and bacterial community, and the co-occurrence between the bacterial community and ARGs in bulk soil was more complex than that in rhizosphere soil. Together these results suggest that phytoremediation of combined soil pollution was positive but limited, and intercropping resulted in enhanced removal efficiency when compared with sole cropping.