Abstract:   In order to obtain a Fenton technique in situ for effective oxidation of total petroleum hydrocarbons (TPH) from soils, the remediation of oil-contaminated soils was studied by preparing the aggregated iron using fulvic acid (FA) in situ. The investigation focused on the effects of the aggregated iron groups and non-aggregated iron groups on the oxidation effects of the two types of oil-contaminated soils (S1, S2) with different textures and soil organic matter (SOM), as well as the mechanism of the highly efficient in-situ oxidation of TPH in the aggregated iron groups. The results showed that: (1) In oil-contaminated S1 and S2 soils (The initial concentrations of S1 and S2 soils were 16,074.33 mg/kg, 14,528.17 mg/kg, respectively), the oxidation amount of TPH was as high as 7,550.32 mg/kg (S1) and 8,747.78 mg/kg (S2) in the aggregated iron group, which were higher than the corresponding values in the non-aggregated iron group I (6,364.43 mg/kg, 5,730.73 mg/kg). It indicated that the aggregated iron group could remove TPH efficiently from soils. (2) In the S1 and S2 soils, the oxidation rates of medium-chain (C₁₉~C₂₄) were up to 20%, 22%, and long-chain (C₂₅~C₃₀) alkanes were 23%, 20% in the aggregated iron group, which were higher than the corresponding values for the non-aggregated iron group I in S1 soil (17%, 18%) and S2 soil (19%, 12%) respectively. (3) The electron paramagnetic resonance (EPR) technology showed that the intensity of hydroxyl radicals (·OH) in the aggregated iron group (S1, 36.61 a.u; S2, 16.06 a.u.) was higher than the corresponding indicators in the non-aggregated iron group I (S1, 27.78 a.u.; S2, 7.11 a.u.), and the hydroxyl radical durations (S1, 50 h; S2, 55 h) were also higher than the corresponding indexes in the non-aggregated iron group I (S1, 45 h; S2, 40 h). (4) The high contents of FeOOH (S1, 503.52; S2, 850.01) and α-FeOOH (S1, 399.40; S2, 769.62) measured by XPS increased the instantaneous strength and yield of ·OH in the aggregated iron group. The result of 3DEEM confirmed that the standard volume of the fluorescence region of fulvic acid-like in the aggregated iron group (S1, 1,554,047.24 au·nm²; S2, 1,110,373.00 au·nm²) was significantly higher than the corresponding values in the non-aggregated iron group (S1, 1,100,706.21 au·nm²; S2, 716,069.98 au·nm²), which revealed that high contents of FA favored the aggregately of FeOOH and α-FeOOH in soils. Our study indicated that the aggregated iron group achieved efficient catalytic H₂O₂ to remove TPH from soils, providing an economical and effective method for chemical oxidation remediation of oil-contaminated soil in situ.