Under the action of hydrogen peroxide, soil organic matter (SOM) can transform dissolved iron (Fe2+) into the solid phase. Solid iron is bound to SOM (Fe-SOM), and two components are included: iron oxides bound to SOM (Fe-SOM oxides) and organic iron bound to SOM (organic Fe-SOM). In oil-contaminated soil samples with Fe-SOM, total petroleum hydrocarbon (TPH) was degraded by 67%; however, in oil-contaminated soil samples without Fe-SOM, the degradation of TPH was only 6%. In oil-contaminated soil samples with Fe-SOM, 73-86% of the primary alkanes (C-14-C-22 composed 67.5% of TPH) were removed, whereas only 45-65% of the C-12-C-13 and C-22-C-30 alkanes were removed. The 11 types of alkanes (C-12-Cis and C-22-C-30) accounted for only 32.5% of TPH. Obviously, the degradation of TPH by Fe-SOM is independent of its hydrophobicity in the solid phase. The results also demonstrated that at a higher content of Fe-SOM, more hydroxyl radical ((OH)-O-center dot) was produced in the solid phase and more TPH was degraded. Alarge number of (OH)-O-center dot are generated near iron-SOM-oil interface. (C) 2016 Elsevier B.V. All rights reserved.