Enhancement of soil organic matter stability cross-linked with aluminium drove the reallocation of ROSs for the directional oxidation of petroleum hydrocarbons.

Since soil organic matter (SOM) significantly competes with petroleum hydrocarbons to consume reactive oxygen species (ROSs), the efficient remediation of petroleum-contaminated soil by chemical oxidation is limited. In this study, an efficient treatment for the remediation of petroleum-contaminated soil comprising directional oxidation was constructed based on the enhancement of SOM stability. A mechanism was proposed whereby SOM pretreatment with hydrogen peroxide (HP) produced more binding sites, such as O-H, C=O, and C-O, thereby making SOM to be maximally stabilized by forming OM-Al-mineral complexes after adding aluminum salts (AS). The two-dimensional correlation spectroscopy (2D-COS) of the FTIR spectra certified that C-O was more sensitive to HP pretreatment and Al cross-linking. Specifically, the enhancement of SOM stability improved the relative reactivity of ROSs to total petroleum hydrocarbons (TPHs) (k_TPHs), driving approximately 30 % of the ROSs to be transferred for the directional oxidation of TPHs. Under such conditions, the directional oxidation amount of TPHs by activated persulfate was up to 13,083 mg/kg (53.55 %), equivalent to 2.67, 1.82, and 1.39 folds of the control CK, HP, and AS treatments, respectively. Subsequently, indigenous bacteria degraded 10,969 mg/kg (44.90 %) of TPHs during a 60-day incubation. Notably, the expressions of the functional genes related to the biodegradation of alkanes and aromatic hydrocarbons were up-regulated. The final amount of TPHs removal, including directional oxidation and biodegradation, obviously increased to 24,052 mg/kg (98.45 %) in the sequential pretreatment with HP and AS. This study provides a new insight into the efficient remediation of petroleum-contaminated soil by enhancing SOM stability.