Rhamnolipid-modified biochar-enhanced bioremediation of crude oil-contaminated soil and mediated regulation of greenhouse gas emission in soil

Abstract

The application of biochar to contaminated soil is an effective strategy to enhance soil remediation by promoting microbial activity. However, the insufficient bioavailability of petroleum in crude oil-contaminated soil limits its application in contaminated soil. Biosurfactant could improve the remediation efficiency of contaminated soil by improving the bioavailability of petroleum in crude oil-contaminated soil. The combination of rhamnolipid and biochar was used to improve the bioremediation efficiency in bioremediation of oil-contaminated soil. Here, three types of biomass were applied to produce biochar including rice husk (BC), sewage sludge (SC), and petroleum coke (PC). Rhamnolipid was used to modify biochar for assessing their effect in bioremediation of oil-contaminated soil. The rhamnolipid-modified biochar was added to oil-contaminated soil with loading rate of 2% (wt/wt) for a 3-month experiment. Soil properties, greenhouse gas (GHG) emission, and microbial community compositions were characterized. The application of rhamnolipid-modified biochar exhibited better performance regarding the degradation of petroleum hydrocarbons, diversity, and abundance of microbial communities and degradation of n-alkanes and PAHs than pristine biochar. Besides, the application of biochar played an important role in the bioavailability of indigenous microbial communities for biodegrading of short-chain hydrocarbon. Meanwhile, the biochar amendments increased the emission of CO2 and CH4, while reduced the emission of N2O. The application of rhamnolipid-modified biochar could improve the diversity and abundance of microbial communities and then promote the degradation of n-alkanes and PAHs, providing an effective approach for bioremediation of crude oil-contaminated soil.