Observations of total RONO2 over the boreal forest: NOx sinks and HNO3 sources
Observations of total RONO2 over the boreal forest: NOx sinks and HNO3 sources
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DOI：
10.5194/acp-13-4543-2013
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发表时间：
2013-01-01
影响因子：
6.3
通讯作者：
Cohen, R. C.
中科院分区：
文献类型：
--
作者：
Browne, E. C.;Min, K. -E.;Cohen, R. C.
与HNO 3形成是氮氧化物主要汇的远程化学教科书观点相反，最近的理论分析表明，异戊二烯和其他萜烯前体形成RONO 2（Sigma ANs）是氮氧化物浓度低的远程大陆上氮氧化物的主要净化学损失。这就增加了关于Sigma AN的化学寿命和最终命运的问题的突出性。我们目前的观察，在加拿大北方森林收集的氮氧化物和有机分子在夏季，这表明，西格玛ANs占类似的总氧化氮的20%，其瞬时生产率大于硝酸。这证实了在遥远的大陆环境中，产生Sigma AN的反应作为对NOx（NOx = NO+ NO2）寿命的控制的主要作用。然而，HNO 3通常以比Sigma AN更大的浓度存在，表明Sigma AN的大气寿命比HNO 3寿命短。我们研究了一系列建议的损失机制，这些机制将解释Sigma AN的推断寿命，发现与沉积相结合，两个过程与观察结果一致：（1）异戊二烯硝酸盐的快速臭氧分解，其中至少有40%的臭氧分解产物从碳骨架释放NOx和/或（2）以HNO 3为产物的颗粒有机硝酸盐的水解。这些想法的影响，我们了解NOx和NOy预算在偏远地区和农村地区进行了讨论。
In contrast with the textbook view of remote chemistry where HNO3 formation is the primary sink of nitrogen oxides, recent theoretical analyses show that formation of RONO2 (Sigma ANs) from isoprene and other terpene precursors is the primary net chemical loss of nitrogen oxides over the remote continents where the concentration of nitrogen oxides is low. This then increases the prominence of questions concerning the chemical lifetime and ultimate fate of Sigma ANs. We present observations of nitrogen oxides and organic molecules collected over the Canadian boreal forest during the summer which show that Sigma ANs account for similar to 20% of total oxidized nitrogen and that their instantaneous production rate is larger than that of HNO3. This confirms the primary role of reactions producing Sigma ANs as a control over the lifetime of NOx (NOx = NO+ NO2) in remote, continental environments. However, HNO3 is generally present in larger concentrations than Sigma ANs indicating that the atmospheric lifetime of Sigma ANs is shorter than the HNO3 lifetime. We investigate a range of proposed loss mechanisms that would explain the inferred lifetime of Sigma ANs finding that in combination with deposition, two processes are consistent with the observations: (1) rapid ozonolysis of isoprene nitrates where at least similar to 40% of the ozonolysis products release NOx from the carbon backbone and/or (2) hydrolysis of particulate organic nitrates with HNO3 as a product. Implications of these ideas for our understanding of NOx and NOy budget in remote and rural locations are discussed.