The role of humic substance-associated persistent free radicals (PFRs) in the fate of organic contaminants under various redox conditions remains unknown. This study examined the characterization of original metal-free peat humin (HM), and HM treated with varying concentrations of H₂O₂ and L-ascorbic acid (VC) (assigned as H₂O₂-HM and VC-HM). The concentration of PFRs in HM increased with the addition of VC/H₂O₂ at concentrations less than 0.08 mol/L. The evolution of PFRs in HM under different environmental conditions (e.g., oxic/anoxic and humidity) was investigated. Two types of PFRs were detected in HM: a relatively stable radical existed in the original sample, and the other type, which was generated by redox treatments, was relatively unstable. The spin densities of VC/H₂O₂-HM readily returned to the original value under relatively high humidity and oxic conditions. During this process, the HM-associated “unstable” free radicals released an electron to O₂, inducing the formation of reactive oxygen species (ROS, i.e., ^⦁OH and ^⦁O₂⁻). The generated ROS promoted the degradation of polycyclic aromatic hydrocarbons based on the radical quenching measurements. The transformation rates followed the order naphthalene>phenanthrene>anthracene>benzo[a]pyrene. Our results provide valuable insight into the HM-induced transformation of organic contaminants under natural conditions.

在各种氧化还原条件下，腐殖质相关的持久性自由基（PFR）在有机污染物的归宿中的作用仍然未知。这项研究检查了原始的无金属泥炭腐殖质（HM）的特性，以及用不同浓度的H ₂ O ₂和L-抗坏血酸（VC）（分别称为H ₂ O ₂ -HM和VC-HM）处理的HM。随着VC / H ₂ O ₂的加入，HM中PFR的浓度增加。浓度小于0.08 mol / L。研究了在不同环境条件（例如，有氧/缺氧和湿度）下HM中PFR的演变。在HM中检测到两种类型的PFR：一种是在原始样品中存在相对稳定的自由基，另一种是通过氧化还原处理生成的，相对不稳定。VC / H ₂ O ₂ -HM的自旋密度在相对较高的湿度和高氧条件下很容易恢复到原始值。在此过程中，HM-相关的“不稳定”自由基释放电子至O ₂，诱导反应性氧物质（ROS，形成即^⦁ OH和^⦁ ö ₂ ^-）。基于自由基猝灭测量，所产生的ROS促进了多环芳烃的降解。转化率依次为萘>菲>蒽>苯并[a] py。我们的结果为在自然条件下HM诱导的有机污染物转化提供了宝贵的见识。