The aim of this study was to determine the remediation efficiency of petroleum-contaminated soil from an oilfield using different types of remediation treatments under laboratory conditions. Compared with unamended soil as the control treatment (T1), soil samples were amended with bulrush straw powder (T2), with biochar alone (T3) and in combination with nutrients (nitrogen and phosphorus) (T4). The remediation experiment was carried out for 8 weeks. The extent of hydrocarbon degradation was monitored gravimetrically, and the residual oil fractions were analyzed by gas chromatography. The characteristics of the polluted soil (water-holding capacity and nutrients) were improved significantly by biochar addition (p < 0.05). The total microbial count increased significantly in the treatment containing biochar and added nutrients (t = 23.429, p = 0.002). The degradation of total petroleum hydrocarbons (TPH) and the main hydrocarbon fractions was higher in T3 and T4, especially in T4, than in T1 and T2. The intensities of the n-alkane fraction, C27-C29 steranes and C33-C35 homohopanes were efficiently decreased in T4 compared to the other treatments. According to the results, petroleum-contaminated soil can be remediated efficiently by adding biochar and nutrients simultaneously, and this combination of remediation was superior to that observed with added bulrush straw powder.
Keywords: Biochar; Microorganisms; Nutrients; Petroleum hydrocarbons.