Ryder Olivia S, Campbell Nicole R, Morris Holly, Forestieri Sara, Ruppel Matthew J, Cappa Christopher, Tivanski Alexei, Prather Kimberly, Bertram Timothy H
Department of Chemistry and Biochemistry, University of California , San Diego, California 92093, United States.
Department of Chemistry, University of Iowa , Iowa City, Iowa 52242, United States.
J Phys Chem A. 2015 Dec 3;119(48):11683-92. doi: 10.1021/acs.jpca.5b08892. Epub 2015 Nov 17.
Previous laboratory measurements and field observations have suggested that the reactive uptake of N2O5 to sea spray aerosol particles is a complex function of particle chemical composition and phase, where surface active organics can suppress the reactive uptake by up to a factor of 60. To date, there are no direct studies of the reactive uptake of N2O5 to nascent sea spray aerosol that permit assessment of the role that organic molecules present in sea spray aerosol (SSA) may play in suppressing or enhancing N2O5 uptake kinetics. In this study, SSA was generated from ambient seawater and artificial seawater matrices using a Marine Aerosol Reference Tank (MART), capable of producing nascent SSA representative of ambient conditions. The reactive uptake coefficient of N2O5 (γ(N2O5)) on nascent SSA was determined using an entrained aerosol flow reactor coupled to a chemical ionization mass spectrometer for measurement of surface area dependent heterogeneous loss rates. Population averaged measurements of γ(N2O5) for SSA generated from salt water sequentially doped with representative organic molecular mimics, or from ambient seawater, do not deviate statistically from that observed for sodium chloride (γ(N2O5)NaCl = 0.01-0.03) for relative humidity (RH) ranging between 50 and 65%. The results are consistent with measurements made under clean marine conditions at the Scripps Institution of Oceanography Pier and those conducted on nascent SSA generated in the marine aerosol reference tank. The results presented here suggest that organic films present on nascent SSA (at RH greater than 50%) likely do not significantly limit N2O5 reactive uptake.
先前的实验室测量和现场观测表明，N₂O₅ 在海浪飞沫气溶胶颗粒上的反应性摄取是颗粒化学成分和相态的复杂函数，其中表面活性有机物可将反应性摄取抑制多达60倍。迄今为止，尚无关于 N₂O₅ 对新生海浪飞沫气溶胶反应性摄取的直接研究，无法评估海浪飞沫气溶胶（SSA）中存在的有机分子在抑制或增强 N₂O₅ 摄取动力学中可能发挥的作用。在本研究中，使用海洋气溶胶参考罐（MART）从环境海水和人工海水基质中生成 SSA，该参考罐能够产生代表环境条件的新生 SSA。使用与化学电离质谱仪耦合的夹带气溶胶流动反应器测定 N₂O₅ 在新生 SSA 上的反应性摄取系数（γ(N₂O₅)），以测量与表面积相关的非均相损失率。对于依次掺杂有代表性有机分子模拟物的盐水或环境海水中生成的 SSA，γ(N₂O₅) 的总体平均测量值在相对湿度（RH）为50%至65%的范围内，与氯化钠（γ(N₂O₅)NaCl = 0.01 - 0.03）的测量值在统计上没有偏差。这些结果与在斯克里普斯海洋学研究所码头的清洁海洋条件下进行的测量以及在海洋气溶胶参考罐中生成的新生 SSA 上进行的测量结果一致。此处呈现的结果表明，新生 SSA 上存在的有机膜（在 RH 大于50%时）可能不会显著限制 N₂O₅ 的反应性摄取。
