Persistent free radicals in humin under redox conditions and their impact in transforming polycyclic aromatic hydrocarbons  

作　　者：Hanzhong Jia Yafang Shi Xiaofeng Nie Song Zhao Tiecheng Wang Virender K.Sharma 

机构地区：[1]College of Resources and Environment,Northwest A&F University,Yangling 712100,China [2]State Key Laboratory of Soil Erosion and Dryland Farming on Loess Plateau,Institute of Soil and Water Conservation,Northwest A&F University,Yangling 712100,China [3]Program for the Environment and Sustainability,Department of Occupational and Environmental Health,School of Public Health,Texas A&M University,College Station,TX 77843,USA

出　　处：《Frontiers of Environmental Science & Engineering》2020年第4期213-223,共11页环境科学与工程前沿（英文）

基　　金：This work is supported by the National Natural Science Foundation of China(Grant Nos.41571446 and 41877126);Shaanxi Science Fund for Distinguished Young Scholars(Grant No.2019JC-18);National Key Technologies R&D Program(Grant No.2018 YFC 1802004)。

摘　　要：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,wa s 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-).Th e 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.

关 键 词：Humic substance Polycyclic aromatic hydrocarbons(PAHs) Persistent free radicals(PFRs) Redox Reactive oxygen species(ROS) 

分 类 号：O62[理学—有机化学]