Assessment of nitrogen and phosphorus in the soil of longitudinal direction affected by in-situ oxidation remediation

The application of in-situ chemical oxidative remediation for contaminated soils has attracted extensive attention, but the effects of remediation processes on soil physical and chemical properties are rarely studied. Herein, a ferrous-activated persulphate oxidation system for remediating dibutyl phthalate (DBP)-polluted soil was simulated in the soil column to explore the effects of in-situ oxidative remediation on soil properties in the longitudinal direction. The DBP content in the soil column was used as an indicator of oxidation strength and the correlation between N, P, soil particle size and oxidation strength was analysed. The experiment results showed that the settling performance of polluted soil after remediation improved and the distribution of the soil particle size at 128 nm disappeared after oxidation, indicating that the suspended solids in the experimental soil were mainly fine clay particles. The oxidation system can promote the conversion of organic nitrogen to inorganic nitrogen and migration characteristics of nitrogen and phosphorus, to aggravate the loss of TN and TP in the soil. The average soil particle size (d50), TN, NH4-N, available phosphorus (Ava-P), exchangeable phosphorus (Ex-P) and organic phosphorus(Or-P) were significantly correlated with oxidation strength; and stable pH in the soil column (pH = 3), showing that the changes in the longitudinal direction of d50 (smaller), TN, NH4-N, Ava-P, Ex-P, and Or-P resulted from the weakening of the longitudinal oxidation strength in the direction of the soil column.