Strong anthropogenic control of secondary organic aerosol formation from isoprene in Beijing
Strong anthropogenic control of secondary organic aerosol formation from isoprene in Beijing
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DOI：
10.5194/acp-2019-929
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发表时间：
2019-10
影响因子：
6.3
通讯作者：
D. Bryant;William J. Dixon;J. Hopkins;R. Dunmore;K. Pereira;M. Shaw;F. Squires;T. Bannan;Archit Mehra;S. Worrall;A. Bacak;H. Coe;C. Percival;L. Whalley;D. Heard;Eloise J. Slater;B. Ouyang;T. Cui;J. Surratt;Di Liu;Zongbo Shi;R. Harrison;Yele Sun;Weiqi Xu;A. Lewis;James D. Lee;A. Rickard;J. Hamilton
中科院分区：
文献类型：
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作者：
D. Bryant;William J. Dixon;J. Hopkins;R. Dunmore;K. Pereira;M. Shaw;F. Squires;T. Bannan;Archit Mehra;S. Worrall;A. Bacak;H. Coe;C. Percival;L. Whalley;D. Heard;Eloise J. Slater;B. Ouyang;T. Cui;J. Surratt;Di Liu;Zongbo Shi;R. Harrison;Yele Sun;Weiqi Xu;A. Lewis;James D. Lee;A. Rickard;J. Hamilton
摘要。异戊二烯衍生的二次有机气溶胶（iSOA）是一些森林地区（如热带雨林和美国东南部）有机碳（OC）的重要贡献者。然而，其在人为污染物含量高的城市地区对有机气溶胶的贡献却鲜为人知。在本研究中，我们考察了中国北京夏季受人为影响的iSOA的形成。当地的异戊二烯排放以及高水平的人为污染物，特别是氮氧化物（NOx）和颗粒态硫酸根（SO42 -），导致在高氮氧化物和低氮氧化物氧化条件下均形成了iSOA，异戊二烯衍生的氧化产物发生显著的非均相转化，形成颗粒态有机硫酸盐（OSs）和硝基氧基 - 有机硫酸盐（NOSs）。超高效液相色谱与高分辨率质谱联用，并结合一种快速自动化数据处理技术，对离线PM2.5滤膜提取物中的31种拟议的iSOA示踪物进行定量。提取物中无机离子的共流出导致基质效应，对两种标准品产生不同影响。iSOA的OSs和NOSs的平均浓度为82.5纳克/立方米，比其氧化前体（2 - 甲基丁四醇和2 - 甲基甘油酸）的观测浓度高约3倍。有机硫酸盐的形成取决于光化学以及可用于反应性吸收的硫酸盐，这表现为其与臭氧（O3）和颗粒态硫酸盐（SO42 -）的乘积有很强的相关性。与之前在污染较轻环境中的研究相比，在北京观察到更高比例的高氮氧化物有机硫酸盐产物。iSOA衍生的OSs和NOSs平均占气溶胶质谱仪测量的氧化有机气溶胶的0.62%，但在某些日子会增加到约3%。这些结果首次表明，北京城市中的iSOA形成受到人为排放的强烈控制，并导致通过非均相反应广泛转化为有机硫酸盐产物。
Abstract. Isoprene-derived secondary organic aerosol (iSOA) is a significant contributor to organic carbon (OC) in some forested regions, such as tropical rainforests and the Southeastern US. However, its contribution to organic aerosol in urban areas that have high levels of anthropogenic pollutants is poorly understood. In this study, we examined the formation of anthropogenically influenced iSOA during summer in Beijing, China. Local isoprene emissions and high levels of anthropogenic pollutants, in particular NOx and particulate SO42-, led to the formation of iSOA under both high- and low-NO oxidation conditions, with significant heterogeneous transformations of isoprene-derived oxidation products to particulate organosulfates (OSs) and nitrooxy-organosulfates (NOSs). Ultra-high-performance liquid chromatography coupled to high-resolution mass spectrometry was combined with a rapid automated data processing technique to quantify 31 proposed iSOA tracers in offline PM2.5 filter extracts. The co-elution of the inorganic ions in the extracts caused matrix effects that impacted two authentic standards differently. The average concentration of iSOA OSs and NOSs was 82.5 ng m−3, which was around 3 times higher than the observed concentrations of their oxygenated precursors (2-methyltetrols and 2-methylglyceric acid). OS formation was dependant on both photochemistry and the sulfate available for reactive uptake, as shown by a strong correlation with the product of ozone (O3) and particulate sulfate (SO42-). A greater proportion of high-NO OS products were observed in Beijing compared with previous studies in less polluted environments. The iSOA-derived OSs and NOSs represented 0.62 % of the oxidized organic aerosol measured by aerosol mass spectrometry on average, but this increased to ∼3 % on certain days. These results indicate for the first time that iSOA formation in urban Beijing is strongly controlled by anthropogenic emissions and results in extensive conversion to OS products from heterogenous reactions.