生物质燃烧排放PM_(2.5)颗粒萃取的水溶性有机碳液相光化学氧化  

Aqueous-phase photochemical oxidation of extracted WSOC in PM_(2.5) from biomass burning

作　　者：朱龙伟 崔尧嘉 盖鑫磊 叶招莲[1] 赵竹子 ZHU Long-wei;CUI Yao-jia;GE Xin-lei;YE Zhao-lian;ZHAO Zhu-zi(School of Resources and Environmental Engineering,Jiangsu University of Technology,Changzhou 213001,China;Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control,School of Environmental Science and Engineering,Nanjing University of Information Science&Technology,Nanjing 210044,China)

机构地区：[1]江苏理工学院资源与环境工程学院,常州213001 [2]南京信息工程大学环境科学与工程学院,江苏省大气环境监测与污染控制高技术研究重点实验室,南京210044

出　　处：《中国环境科学》2023年第3期1014-1025,共12页China Environmental Science

基　　金：江苏省自然科学基金项目(BK20221405);江苏省普通高校专业学位研究生实践创新计划项目(SJCX21_1332);江苏理工学院研究生实践创新计划项目(XSJCX21_64)。

摘　　要：为探究生物质燃烧排放的PM_(2.5)中水溶性有机碳(WSOC)的液相氧化特征,探索了两种生物质(小麦秸秆和水稻秸秆)燃烧排放的WSOC在紫外光(UV)和紫外光+H_(2)O_(2)体系(UV+OH)液相氧化产物的吸光特性、荧光特性及氧化特性.总有机碳分析仪的分析结果表明两个体系中WSOC去除率相当,增加H_(2)O_(2)并未明显改善去除率,推测直接光解是WSOC降解的主要途径;两种生物质燃烧PM_(2.5)中WSOC降解速率均较快,光照17h后WSOC去除率均在70%左右.两种生物质WSOC液相光化学氧化产物变化规律没有显著差别.随着光解进行,WSOC的降解导致吸光度不断下降,三维荧光(EEM)光谱图中的荧光峰Ex/Em=255~260nm/330~340nm强度也不断下降,但Ex/Em=230/400~500nm出现了新的荧光峰,说明可能生成了类腐殖质(HULIS).高分辨气溶胶质谱仪(HR-AMS)分析的aqSOA生成潜势及其氧化特性,结果表明,随反应进行,尽管两种体系中aqSOA不断降低,但由于产物中含氧官能比例增加,aqSOA比反应前更具氧化性.产物的氧化潜势变化规律与HULIS变化规律相似,在UV+OH体系中先升高后下降,归因于反应初期含氧官能团物质的生成及随后的降解.结合以上研究结果,推测燃烧排放WSOC液相氧化经历了官能团化生成高一代产物后,碎片化和开环反应形成二代、三代氧化性更强的小分子产物,从而可能间接影响气候变化和空气质量.本文揭示生物质燃烧排放WSOC老化行为对于理解液相氧化反应对吸光性、SOA形成及健康影响等方面具有重要意义.To explore aqueous-phase oxidation characteristics of extracted water soluble organic carbon(WSOC)in PM_(2.5)emitted from biomass burning,this study investigated the absorption,fluorescence and the oxidation properties of WSOC from two types of biomass burning(wheat and rice straws)under ultraviolet(UV)and UV+H_(2)O_(2)(UV+OH)conditions.The results from total organic carbon(TOC)analyzer showed that WSOC removal rates were almost the same in the two conditions.Extra H_(2)O_(2)adding didn’t improve the removal rates of WSOC,indicating direct photolysis was the major degradation pathway of WSOC.The removal rates of WSOC for wheat straw in two types of biomass burning samples were relatively fast,reducing about 70%in 17hours.No significant differences were found in aqueous-phase photochemical oxidation products between rice straw and wheat straw burning samples.With the photolysis process,absorbance decreased gradually due to WSOC degradation,and fluorescence intensity at excitation/emission(Ex/Em)255~260nm/330~340nm also declined.However,new fluorescent peaks at Ex/Em=230/(400~500)nm appeared,which could might be ascribed to the formation of humic-like substance(HULIS).Besides,high-resolution aerosol mass spectra(HR-AMS)was used to investigate aqSOA formation potential and its oxidation characteristics.The results showed that the mass of aqSOA decreased while aqSOA became more oxidative owing to the content of O-containing functional groups increasing as aging.The variation of oxidative potential(OPs)was similar to that of HULIS,with rose at first and then declined in UV+OH condition,which could be attributed to the formation of O-containing functional groups at first stage and subsequent degradation.Based on the above analysis results,we infer that the process of aqueous-phase oxidation of WSOC undergo functionalization to form the first generation products,then to more oxidized second-and third-generation smaller species formed by fragmentation and ring-opening reactions,which in turn indirectly impact climate c

关 键 词：生物质燃烧 水溶性有机碳 液相氧化 荧光特性 氧化潜势 

分 类 号：X513[环境科学与工程—环境工程]