School of Chemical and Biomolecular Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332, United States.
School of Earth and Atmospheric Sciences, Georgia Institute of Technology , Atlanta, Georgia 30332, United States.
Environ Sci Technol. 2016 Jan 5;50(1):222-31. doi: 10.1021/acs.est.5b04594. Epub 2015 Dec 16.
The nitrate radical (NO3) is the dominant nighttime oxidant in most urban and rural environments and reacts rapidly with biogenic volatile organic compounds to form secondary organic aerosol (SOA) and organic nitrates (ON). Here, we study the formation of SOA and ON from the NO3 oxidation of two monoterpenes (α-pinene and β-pinene) and investigate how they evolve during photochemical aging. High SOA mass loadings are produced in the NO3+β-pinene reaction, during which we detected 41 highly oxygenated gas- and particle-phase ON possessing 4 to 9 oxygen atoms. The fraction of particle-phase ON in the β-pinene SOA remains fairly constant during photochemical aging. In contrast to the NO3+β-pinene reaction, low SOA mass loadings are produced during the NO3+α-pinene reaction, during which only 5 highly oxygenated gas- and particle-phase ON are detected. The majority of the particle-phase ON evaporates from the α-pinene SOA during photochemical aging, thus exhibiting a drastically different behavior from that of β-pinene SOA. Our results indicate that nighttime ON formed by NO3+monoterpene chemistry can serve as either permanent or temporary NOx sinks depending on the monoterpene precursor.
硝酸根自由基（NO3）是大多数城市和农村环境中占主导地位的夜间氧化剂，它与生物源挥发性有机化合物迅速反应，形成二次有机气溶胶（SOA）和有机硝酸盐（ON）。在这里，我们研究了两种单萜（α-蒎烯和β-蒎烯）的 NO3 氧化形成 SOA 和 ON 的过程，并研究了它们在光化学老化过程中的演变。NO3+β-蒎烯反应产生高 SOA 质量负荷，在此期间，我们检测到 41 种具有 4 到 9 个氧原子的高度含氧的气相和颗粒相 ON。在光化学老化过程中，β-蒎烯 SOA 中颗粒相 ON 的比例保持相当稳定。与 NO3+β-蒎烯反应不同，NO3+α-蒎烯反应产生低 SOA 质量负荷，在此期间仅检测到 5 种高度含氧的气相和颗粒相 ON。大多数颗粒相 ON 从α-蒎烯 SOA 中蒸发出来，因此其行为与β-蒎烯 SOA 截然不同。我们的结果表明，NO3+单萜化学形成的夜间 ON 可以根据单萜前体作为永久性或临时性的 NOx 汇。
