Composition, concentration, and oxidant reactivity of sesquiterpenes in the southeastern U.S.
Composition, concentration, and oxidant reactivity of sesquiterpenes in the southeastern U.S.
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美国东南部倍半萜的组成、浓度和氧化剂反应性
DOI：
10.1039/d2ea00059h
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发表时间：
2022
期刊：
影响因子：
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通讯作者：
Isaacman-VanWertz, Gabriel
中科院分区：
文献类型：
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作者：
Frazier, Graham;McGlynn, Deborah F.;Barry, Laura E.;Lerdau, Manuel;Pusede, Sally E.;Isaacman-VanWertz, Gabriel
生物源挥发性有机化合物（BVOCs）向大气中贡献了大部分活性有机碳，并通过与包括臭氧和羟基自由基的大气氧化剂反应而导致气溶胶形成。一类BVOCs，即倍半萜烯，与臭氧有很高的反应性，但与其他BVOCs相比，其浓度较低，并且对其在不同环境中的浓度或其在大气氧化剂预算中的重要性的测量相对较少。为了帮助缩小这一知识差距，我们检查浓度的异构体解析倍半萜浓度每小时收集在弗吉尼亚州的两个网站，代表不同的生态系统在美国东南部。倍半萜浓度的介绍和讨论有关其昼夜模式，并用于估计其贡献与常见的气相氧化剂的反应。24个倍半萜被确定在网站，其中11个观察到在这两个网站。发现总倍半萜浓度范围在0.8和2 ppt之间，没有单一异构体占主导地位。羟基活性也是类似的多样性，在任何一个位点都没有特定的异构体主导活性。然而，发现臭氧反应性由β-香芹烯和蛇麻烯主导（约3/4总反应性），尽管这些化合物仅占总倍半萜质量的大约10%，突出了它们作为倍半萜-臭氧反应性的主要驱动因素的重要性。平均反应速率常数的倍半萜与臭氧和羟基自由基计算两个网站作为一种方法，以简化未来的大气模型有关倍半萜。这项工作提供了广泛的洞察组成和倍半萜的影响，表明倍半萜组成是相对相似的网站之间。此外，虽然计算出的平均倍半挥发性有机化合物-臭氧反应速率常数至少比更普遍的BVOC类（异戊二烯和单萜）高一个数量级，但其低浓度表明其对大气反应性的影响预计仅限于高排放时期。
Biogenic volatile organic compounds (BVOCs) contribute the majority of reactive organic carbon to the atmosphere and lead to aerosol formation through reaction with atmospheric oxidants including ozone and hydroxyl radicals. One class of BVOCs, sesquiterpenes, have a high reactivity with ozone but exist at lower concentrations compared to other BVOCs, and there are relatively few measurements of their concentrations in different environments or their importance in the atmospheric oxidant budget. To help close this knowledge gap, we examine concentrations of isomer-resolved sesquiterpene concentrations collected hourly at two sites in Virginia that are representative of different ecosystems in the southeastern US. Sesquiterpene concentrations are presented and discussed in relation to their diurnal patterns and used to estimate their contribution to reactivity with common gas-phase oxidants. Twenty-four sesquiterpenes were identified at the sites, eleven of which were observed at both sites. Total sesquiterpene concentrations were found to range between 0.8 and 2 ppt with no single isomer dominating throughout. Hydroxyl activity is similarly diverse, with no particular isomer dominating activity at either site. Ozone reactivity, however, was found to be dominated (∼3/4 total reactivity) by β-caryophyllene and humulene despite these compounds representing roughly only 10% of total sesquiterpene mass, highlighting their importance as the major driver of sesquiterpene-ozone reactivity. Average reaction rate constants for sesquiterpenes with ozone and hydroxyl radicals were calculated for both sites as a method to simplify future atmospheric modelling concerning sesquiterpenes. This work provides broad insight into the composition and impacts of sesquiterpenes, suggesting that sesquiterpene composition is relatively similar between sites. Furthermore, while the calculated average sesquiterpene-ozone reaction rate constants are at least an order of magnitude higher than that of more prevalent BVOC classes (isoprene and monoterpenes), their low concentrations suggest their impacts on atmospheric reactivity are expected to be limited to periods of high emissions.