• • In black soil, 2,6-DCP achieved 85.1% oxidative transformation within 3 days, demonstrating the highest reactivity among the three soils; this underscores the potential of black soil for natural attenuation of chlorophenols.
• • The oxidative coupling reaction is endothermic, meaning that increasing temperature enhances reaction rates; this thermodynamic property is critical for predicting field performance under varying climatic conditions.
• • Soil microorganisms and dissolved oxygen synergistically drive the oxidative coupling; sterilization experiments showed significantly reduced degradation, confirming the biotic-abiotic coupling mechanism.
• • UPLC-MS/MS identified OH-PCDEs and OH-PCBs as major products, with DFT calculations confirming structures such as 4-hydroxy-2',3,5,6'-tetrachlorodiphenyl ether and 4,4'-dihydroxy-3,3',5,5'-tetrachlorobiphenyl, indicating C-C and C-O coupling pathways.