Aircraft observations of the lower troposphere above a megacity: Alkyl nitrate and ozone chemistry
Aircraft observations of the lower troposphere above a megacity: Alkyl nitrate and ozone chemistry
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DOI：
10.1016/j.atmosenv.2014.05.040
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发表时间：
2014-09
影响因子：
5
通讯作者：
E. Aruffo;P. Carlo;C. Dari-Salisburgo;F. Biancofiore;F. Giammaria;M. Busilacchio;James D. Lee;S. Moller;J. Hopkins;S. Punjabi;S. Bauguitte;D. O’Sullivan;C. Percival;M. Breton;J. Muller;R. L. Jones;G. Forster;C. Reeves;D. Heard;H. Walker;T. Ingham;S. Vaughan;D. Stone
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文献类型：
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作者：
E. Aruffo;P. Carlo;C. Dari-Salisburgo;F. Biancofiore;F. Giammaria;M. Busilacchio;James D. Lee;S. Moller;J. Hopkins;S. Punjabi;S. Bauguitte;D. O’Sullivan;C. Percival;M. Breton;J. Muller;R. L. Jones;G. Forster;C. Reeves;D. Heard;H. Walker;T. Ingham;S. Vaughan;D. Stone
在RONOCO（夜间化学在控制大气氧化能力中的作用）活动的框架内，在伦敦大都市上空进行了一次白天飞行，以研究氮氧化物化学及其在臭氧（O3）和烷基及多官能硝酸盐（HNOAN）的产生和损失中的作用。用于这些观测的FAAM BAe-146飞机配备了测量控制低对流层化学的最相关化合物的仪器，包括O3，NO，NO2，NO3，N2 O 5，HNO 3，过氧硝酸盐（HNOPN），HNOAN，OH和HO 2。在伦敦号的飞行中，当飞越阅读（伦敦的下风处）和拦截伦敦羽流时，观察到了一个强烈的臭氧滴定过程。NOx和HOx的耦合循环可以具有不同的终止形式，形成HNO 3或过氧化物（H2 O2，ROOH），从而改变O3的产生。在这里报告的观察中，我们发现，由于NOx的快速增加（ΔNOx= 27 ppb），强烈的臭氧滴定（ΔO3= −16 ppb）也对应于HNO 3和HNO 3的浓度的高增加（Δ HNO 3 = 3 ppb）和相当稳定的浓度。出乎意料的是，与其他大城市相比，CO2的产生与Ox（O3+NO2）相似，这表明在伦敦羽流中，至少在这些观测期间，CO2的形成有效地去除了活性NOx，从而减少了O3的产生量。事实上，我们发现，臭氧的生产和硝酸烷基酯的生产（观察）之间的比例接近统一;相反，计算的比例是7。为了解释这一差异，我们进行了敏感性测试，改变了一些VOC的硝酸烷基酯分支比，我们研究了飞行过程中未测量的VOC的影响，发现计算的比率从7下降到2，在这种情况下，烷烃对C2 H4生成的主要贡献。本文报道的观测和分析表明，在伦敦烟羽中，高氮氧化物排放和某些挥发性有机化合物（主要是烷烃）的化学性质产生了高浓度的氮氧化物，与当地的臭氧生产竞争。
Within the framework of the RONOCO (ROle of Nighttime chemistry in controlling the Oxidising Capacity of the atmOsphere) campaign a daytime flight over the metropolitan area of London were carried out to study the nitrogen oxide chemistry and its role in the production and loss of ozone (O3) and alkyl and multifunctional nitrate (ΣANs). The FAAM BAe-146 aircraft, used for these observations, was equipped with instruments to measure the most relevant compounds that control the lower troposphere chemistry, includingO3,NO,NO2,NO3,N2O5,HNO3, peroxy nitrates (ΣPNs),ΣANs,OH, andHO2. In the London's flight a strong ozone titration process was observed when flying above Reading (downwind of London) and when intercepting the London plume. The coupled cycles ofNOxandHOxcan have different terminations formingΣPNs,ΣANs,HNO3or peroxides (H2O2, ROOH) altering theO3production. In the observations reported here, we found that a strong ozone titration (ΔO3= −16 ppb), due to a rapid increase ofNOx(ΔNOx= 27 ppb), corresponds also to a high increase ofΣANsconcentrations (ΔΣANs= 3 ppb), and quite stable concentrations of HNO3and ΣPNs. Unexpectedly, compared with other megacities, the production ofΣANsis similar to that ofOx(O3+NO2), suggesting that in the London plume, at least during these observations, the formation ofΣANseffectively removes activeNOxand hence reduces the amount ofO3production. In fact, we found that the ratio between the ozone production and the alkyl nitrates production (observed) approximate the unity; on the contrary the calculated ratio is 7. In order to explain this discrepancy, we made sensitivity tests changing the alkyl nitrates branching ratio for some VOCs and we investigated the impact of the unmeasured VOCs during the flight, founding that the calculated ratio decreases from 7 to 2 and that, in this condition, the major contribution to theΣANsproduction is given by Alkanes. Observations and analysis reported here suggest that in the London plume the highNOxemissions and the chemistry of someVOCs(mainly Alkanes) produce high concentrations ofΣANscompeting against the local ozone production.