On the role of monoterpene chemistry in the remote continental boundary layer
On the role of monoterpene chemistry in the remote continental boundary layer
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DOI：
10.5194/acp-14-1225-2014
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发表时间：
2014-01-01
影响因子：
6.3
通讯作者：
Cohen, R. C.
中科院分区：
文献类型：
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作者：
Browne, E. C.;Wooldridge, P. J.;Cohen, R. C.
有机硝酸盐（RONO₂）的形成是偏远和乡村大陆大气中重要的氮氧化物（NOₓ = NO + NO₂）汇，因此会影响臭氧的产生和二次有机气溶胶（SOA）的形成。在这些偏远和乡村环境中，有机硝酸盐主要来源于生物源挥发性有机化合物（BVOCs），如异戊二烯和单萜烯。尽管有大量研究调查单萜烯形成二次有机气溶胶的情况，但研究单萜烯气相化学的却很少。我们利用一个对有机硝酸盐化学有扩展表述的区域化学传输模型，研究了加拿大北方森林上方单萜烯硝酸盐（MTNs）的产生和归宿的控制过程。在北方森林上方，单萜烯硝酸盐占总氧化氮的5 - 12%，当氮氧化物混合比大于75 pptv时，通过NO₃化学过程的产生比通过OH的产生更为重要。针对单萜烯硝酸盐的两种氧化途径研究了区域响应：一种是将氮氧化物返回大气，另一种是将单萜烯硝酸盐转化为类似硝酸（HNO₃）的硝酸盐。实际情况可能介于两者之间，这两种假设涵盖了这种化学过程的不确定性。在单萜烯硝酸盐氧化后返回氮氧化物的情况下，它们的形成代表了一种净化学氮氧化物损失，该损失超过了过氧硝酸盐形成所导致的净损失。当单萜烯硝酸盐氧化产生一种类似硝酸的分子时，硝酸和单萜烯硝酸盐几乎是同等重要的氮氧化物化学汇。单萜烯硝酸盐氧化归宿的这种不确定性导致在两种模型模拟之间，氮氧化物变化为8 - 14%，臭氧变化高达3%，羟基变化为3 - 6%。
The formation of organic nitrates (RONO2) represents an important NOx (NOx = NO+NO2) sink in the remote and rural continental atmosphere, thus impacting ozone production and secondary organic aerosol (SOA) formation. In these remote and rural environments, the organic nitrates are primarily derived from biogenic volatile organic compounds (BVOCs) such as isoprene and monoterpenes. Although there are numerous studies investigating the formation of SOA from monoterpenes, there are few studies investigating monoterpene gas-phase chemistry. Using a regional chemical transport model with an extended representation of organic nitrate chemistry, we investigate the processes controlling the production and fate of monoterpene nitrates (MTNs) over the boreal forest of Canada. MTNs account for 5-12% of total oxidized nitrogen over the boreal forest, and production via NO3 chemistry is more important than production via OH when the NOx mixing ratio is greater than 75 pptv. The regional responses are investigated for two oxidation pathways of MTNs: one that returns NOx to the atmosphere and one that converts MTNs into a nitrate that behaves like HNO3. The likely situation is in between, and these two assumptions bracket the uncertainty about this chemistry. In the case where the MTNs return NOx after oxidation, their formation represents a net chemical NOx loss that exceeds the net loss to peroxy nitrate formation. When oxidation of MTNs produces a molecule that behaves like HNO3, HNO3 and MTNs are nearly equal chemical sinks for NOx. This uncertainty in the oxidative fate of MTNs results in changes in NOx of 8-14 %, in O-3 of up to 3 %, and in OH of 3-6% between the two model simulations.