Al(Ⅲ)-蒙脱土界面苯并[a]芘的转化及环境持久性自由基的形成机制  

Transformation of benzo[a]pyrene on Al(Ⅲ)-montmorillonite:Mechanism of environmental persistent radicals formation

作　　者：赵松 刘晋波[1] 石亚芳 苗铎 张弛 贾汉忠 祝凌燕 Song Zhao;Jinbo Liu;Yafang Shi;Duo Miao;Chi Zhang;Hanzhong Jia;Lingyan Zhu(College of Natural Resources and Environment,Northwest A&F University,Yangling 712100,China;State Key Laboratory of Soil Erosion&.Dryland Farming on the Loess Plateau,Institute of Soil&Water Conservation,Northwest A&F University,Yangling 712100,China)

机构地区：[1]西北农林科技大学资源环境学院,杨凌712100 [2]西北农林科技大学水土保持研究所,黄土高原土壤侵蚀与旱地农业国家重点实验室,杨凌712100

出　　处：《科学通报》2021年第2期233-243,共11页Chinese Science Bulletin

基　　金：国家自然科学基金(41877126)资助。

摘　　要：无机矿物主导的非生物转化过程是土壤中有机污染物自然衰减的主要途径,而目前有关Al(Ⅲ)饱和黏土矿物界面多环芳烃(polycyclic aromatic hydrocarbons,PAHs)的转化过程与产物鲜有报道.本研究选取强致癌化合物:苯并[a]芘(benzo[a]pyrene,B[a]P)为研究对象,采用电子顺磁共振技术对蒙脱土表面B[a]P转化过程中形成的环境持久性自由基(environmentally persistent free radicals,EPFRs)进行定量研究.分析了在不同相对湿度(relative humidity,RH)条件下,B[a]P/Al(Ⅲ)-蒙脱土界面EPFRs的形成与稳定.结果表明,蒙脱石表面Al(Ⅲ)的存在可加快B[a]P的降解,反应速率是Na(Ⅰ)饱和蒙脱石的37倍.在相对干燥的环境条件下(RH<33%),B[a]P的转化和EPFRs的形成不受RH的影响;当RH>97%时会抑制B[a]P的转化和EPFRs的形成.通过活性氧捕获实验和自由基猝灭实验进一步证实了EPFRs的形成过程中伴随着羟基自由基(·OH)和超氧自由基(O_(2)^(·-))的生成,且在B[a]P的转化过程中起到促进作用,进而提出了B[a]P/Al(Ⅲ)-蒙脱土的界面反应机理.本研究对认识土壤环境中PAHs等有机污染物的迁移转化规律和生态风险具有重要的科学意义.Environmental persistent free radicals(EPFRs)have been evaluated as a new kind of environmental risk substance,which are mainly detected in atmospheric particles and superfund sites.Clay minerals,which are composed of layered silicates and are abundant in soil environment,provide an appropriate site for organic pollutants to form EPFRs.Our previous studies showed that combination of clay minerals and transition metal species such as Fe and Cu ions/oxides can effectively degrade polycyclic aromatic hydrocarbons(PAHs),and significant EPFRs signal can be detected by electron paramagnetic resonance(EPR).Aluminum(Al)is the most abundant metal element in the earth’s crust,however,to the best of our knowledge,few studies have reported the formation of EPFRs by organic pollutants contaminated Al(Ⅲ)-clay minerals,and an unambiguous of the relevant interface process and mechanism is still lacking.In this paper,benzo[a]pyrene(B[a]P),a strong carcinogenic PAHs compound,was used to contaminate Al(Ⅲ)-montmorillonite,and Na(I)-montmorillonite served as the control group.The degradation rate of B[a]P was determined by high performance liquid chromatography(HPLC).Fourier transform Infrared spectrometer(FTIR)and X-ray photoelectron spectroscopy(XPS)were employed to analyze the changes of functional groups and elements in the course of degradation of B[a]P.Since water content is an important factor in soil,three different relative humidity(RH)conditions(RH<7%,~33%,>97%)were selected to explore the stability of B[a]P-EPFRs.In order to confirm that the formation of EPFRs was accompanied by generation of hydroxyl radical(·OH)and superoxide radical(O_(2)^(·-)),reactive oxygen species(ROS)capture experiment and radical quenching experiment were carried out.The results confirmed that Al(Ⅲ)-montmorillonite was capable of accelerating the degradation of B[a]P,and the reaction rate was 37 times higher than that of Na(I)-montmorillonite.FTIR characterizations showed that the decay of old functional groups(C=C)was accompanied by for

关 键 词：环境持久性自由基 蒙脱土 苯并[A]芘 降解 活性氧 

分 类 号：X53[环境科学与工程—环境工程]