Remediation of crude oil-contaminated coastal marsh soil: Integrated effect of biochar, rhamnolipid biosurfactant and nitrogen application.

•Biochar, RL, and N are effective in aliphatic and aromatic hydrocarbon remediation.•Biochar, RL, and N show distinctive functions on hydrocarbon degradation.•RL and N promote oil degraders and reduce bacterial community diversity.•Integrated application exhibits the highest efficiency on wetland oil remediation.