Bioremediation of petroleum-contaminated soil by biostimulation amended with biochar

In this study, the effects of rice straw biochar on soil contaminant biodegradation and microbial community compositions were investigated in the laboratory during a 180-day period. The results of soil microcosm experiments showed that contaminant degradation efficiency was significantly higher in soils amended with biochar than in soils without. The adding time of biochar had apparent effects on degradation efficiency. The removal efficiencies of total petroleum hydrocarbons (TPH) were 61.2%, 77.8% and 84.8%, in the soils without biochar, amended with biochar at the beginning or the 80th day respectively. When adding biochar at the 80th day, the TPH concentration decreased to below the threshold level required for Chinese soil quality for TPH (3000 mg kg−1 dry weight) in 140 days. The addition of biochar did not result in appreciable negative impacts on soil microbial community composition. It was speculated that when adding biochar at the 80th day, a large amount of metabolites could be absorbed onto the biochar, leading to significant reduction in soil toxicity and biodegradation enhancement.