基于烟雾箱模拟的异戊二烯夜间臭氧化反应

A chamber study of gas-phase products formation by isoprene nocturnal ozonolysis

通过烟雾箱系统模拟研究了异戊二烯夜间臭氧化反应过程.利用质子转移反应飞行时间质谱仪(PTR-TOF-MS)实时检测异戊二烯-臭氧反应体系中气相产物浓度随反应时间的变化;利用扫描电迁移率颗粒物粒径谱仪(SMPS)实时监测二次有机气溶胶(SOA)的产生过程.结果表明,在反应温度(298±1)K,相对湿度30%的条件下,异戊二烯被臭氧消耗并随之产生SOA,在反应约4h时SOA达到浓度峰值3.14ug/m^(3).异戊二烯夜间臭氧化反应的主要气相产物为C_(1)~C_(4)的含氧挥发性有机物(OVOCs),包括甲醛(HCHO)、甲酸(CH_(2)O_(2))、乙酸(C_(2)H_(4)O_(2))、丙酮(C_(3)H_(6)O)、丙酸(C_(3)H_(6)O_(2))、甲基丙烯醛(MACR)、甲基乙烯基酮(MVK)和甲基丙烯酸(C_4H_6O_(2))等,且产率随着臭氧与异戊二烯比值的变化而变化.HCHO和MACR+MVK在所有反应产物中产率最高,在臭氧与异戊二烯比值为0.5~6.8时,产率范围分别为17.0%~35.6%和59.3%~89.5%.NO_(2)对HCHO和MACR+MVK的生成有较为明显的抑制作用,其它的OVOCs随NO_(2)浓度的增加表现出较为温和的负相关.异戊二烯夜间氧化反应对OVOCs和SOA具有重要贡献.

A chamber experiment was conducted simulate the nighttime ozone oxidation process of isoprene.The concentration changes of gas-phase products in the isoprene-ozone reaction system were monitored in real-time using proton transfer reaction time-of-flight mass spectrometry(PTR-TOF-MS).Furthermore,the production process of secondary organic aerosols(SOA)was assessed in real-time through scanning mobility particulate size spectrometry(SMPS).The findings revealed that under the conditions of a reaction temperature of(298±1)K and a relative humidity of 30%,isoprene was consumed by ozone,resulting in the formation of SOA.The concentration of SOA peaked at 3.14μg/m^(3)approximately 4 hours into the reaction.The main gas-phase products of the nighttime ozone oxidation reaction of isoprene were oxygenated volatile organic compounds(OVOCs)ranging from C_(1)~C_(4),including formaldehyde(HCHO),formic acid(CH_(2)O_(2)),acetic acid(C_(2)H_(4)O_(2)),acetone(C_(3)H_(6)O),propionic acid(C_(3)H_(6)O_(2)),methacrolein(MACR),methyl vinyl ketone(MVK),and methacrylic acid(C_(4)H_(6)O_(2)),and the yields of these products varied with the ratio of ozone to isoprene.Notably,HCHO and MACR+MVK exhibited the highest yields among all oxidation products.When the ozone/isoprene ratio ranged from 0.5 to 6.8,the yield ranges were 17.0%to 35.6%for HCHO and 59.3%to 89.5%for MACR+MVK.Additionally,NO_(2)was found to inhibit the production of HCHO and MACR+MVK,while other OVOCs displayed a mild negative correlation with increasing NO_(2)concentrations.The nighttime oxidation of isoprene plays a significant role in the formation of OVOCs and SOA.