Roles of Natural Phenolic Compounds in Polycyclic Aromatic Hydrocarbons Abiotic Attenuation at Soil-Air Interfaces through Oxidative Coupling Reactions

Phenolicconstituents promoted PAHs detoxification by nonenzymaticoxidative coupling reaction in dry soils, presenting a strategy fororganic carbon sequestration. Littleinformation is available on the roles of natural phenoliccompounds in polycyclic aromatic hydrocarbons (PAHs) attenuation atdry soil-air interfaces. The purpose of this study was to determinethe roles of model phenolic constituents of soil organic matter (SOM)on the abiotic attenuation of PAHs. The phenolic compounds can significantlychange the attenuation rates of PAHs, among which hydroquinone wasthe most effective in promoting anthracene and benzo[a]anthracene attenuation. Product identification and sequential extractionexperiments revealed hydroquinone enhanced the formation of oxidativecoupling products and promoted the incorporation of PAHs into humicanalogues, thereby reducing potential risks to humans and ecosystems.Electron paramagnetic resonance spectroscopy analyses showed bothPAHs and phenolic compounds could donate electrons to Lewis acid sitesof soil minerals, resulting in the generation of persistent free radicals(PFRs). PFRs could promote the generation of & BULL;OH to enhance PAHoxidation and could cross-couple with PAHs, resulting in high-molecular-weightoxidative coupling products. This study revealed for the first timethe reaction mechanism between PAHs and phenolic components of SOMunder relatively dry conditions and provided new insights into promotingPAHs detoxification in soils but also a potential strategy to increasethe organic carbon sequestration.