Secondary Organic Aerosol (SOA) from Nitrate Radical Oxidation of Monoterpenes: Effects of Temperature, Dilution, and Humidity on Aerosol Formation, Mixing, and Evaporation
Secondary Organic Aerosol (SOA) from Nitrate Radical Oxidation of Monoterpenes: Effects of Temperature, Dilution, and Humidity on Aerosol Formation, Mixing, and Evaporation
复制标题
DOI：
10.1021/acs.est.7b01460
复制
发表时间：
2017-07-18
影响因子：
11.4
通讯作者：
Ng, Nga Lee
中科院分区：
文献类型：
--
作者：
Boyd, Christopher M.;Nah, Theodora;Ng, Nga Lee
生物源挥发性有机化合物（BVOC）的硝酸根自由基（NO₃）氧化对夜间二次有机气溶胶（SOA）的形成非常重要。夜间产生的SOA可能会因温度升高或半挥发性化合物的稀释而在第二天早上蒸发。我们在25℃下等温稀释柠檬烯 + NO₃反应的氧化产物，并观察到通过稀释有机气溶胶的蒸发可忽略不计。柠檬烯 + NO₃的SOA产率在25℃时大致恒定（约为174%），在40℃时为81% - 148%。基于两个温度下产率的差异，我们计算出有效汽化焓为117 - 237 kJ/mol。与25℃相比，40℃时的气溶胶产率可能会低50%之多。然而，当在25℃形成的气溶胶被加热到40℃时，只有约20%的气溶胶蒸发，这可能表明气溶胶蒸发存在阻力。为了更好地理解这一点，我们探究了柠檬烯 + NO₃和β - 蒎烯 + NO₃反应产生的SOA具有高粘性的可能性。我们证明了颗粒形态和蒸发取决于柠檬烯的SOA是在β - 蒎烯的SOA形成之前还是期间形成的。即使在高相对湿度（约70%）下，这种颗粒形态的差异仍然存在。
Nitrate radical (NO3) oxidation of biogenic volatile organic compounds (BVOC) is important for nighttime secondary organic aerosol (SOA) formation. SOA produced at night may evaporate the following morning due to increasing temperatures or dilution of semivolatile compounds. We isothermally dilute the oxidation products from the limonene+NO3 reaction at 25 degrees C and observe negligible evaporation of organic aerosol via dilution. The SOA yields from limonene+NO3 are approximately constant (similar to 174%) at 25 degrees C and range from 81 to 148% at 40 degrees C. Based on the difference in yields between the two temperatures, we calculated an effective enthalpy of vaporization of 117-237 kJ mol(-1). The aerosol yields at 40 degrees C can be as much as 50% lower compared to 25 degrees C. However, when aerosol formed at 25 degrees C is heated to 40 degrees C, only about 20% of the aerosol evaporates, which could indicate a resistance to aerosol evaporation. To better understand this, we probe the possibility that SOA from limonene+NO3 and beta-pinene+NO3 reactions is highly-viscous. We demonstrate that particle morphology and evaporation is dependent on whether SOA from limonene is formed before or during the formation of SOA from beta-pinene. This difference in particle morphology is present even at high relative humidity (similar to 70%).