Degradation of Atrazine, Simazine and Ametryn in an arable soil using thermal-activated persulfate oxidation process: Optimization, kinetics, and degradation pathway

Abstract

This study examined the feasibility of applying thermal-activated persulfate (PS) oxidation for remediation of soil co-contaminated with s-triazine herbicides including Atrazine (ATZ), Simazine (SIM) and Ametryn (AME). Homogeneous activation using heating method (50 °C) was selected. Results showed that thermal-activated PS oxidation process may successfully degrade ATZ in soil and degradation efficiency was increased along the arising activation temperature. Higher PS dosages and depressed initial pH were beneficial for degradation while increasing initial ATZ concentration may hamper the degradation. The oxidation process may lead to changes of surface functional groups on soil. The presence of Cl^-, HCO₃^- and H₂PO₄^- at both of low and high concentrations may inhibit the degradation of ATZ. Soil depths may apparently influence the ATZ degradation which followed 0-10 < 10-30 < 30-60 cm mainly depending on the soil organic matter (SOM) contents. Thermal-activated PS may effectively degrade ATZ, SIM and AME under co-contaminated condition and the more favorable of ethyl group towards SO₄^- than isopropyl and methylation groups was detected. Both of SO₄^- and HO were identified to be responsible for degradation. Finally, degradation intermediates of ATZ, SIM and AME were identified by LC-Q-TOF-MS and detailed transformation pathways for three pesticides were proposed, respectively.

Keywords: Degradation mechanisms; Soil depths; Sulfate radical-based oxidation; s-Triazine herbicides.