Alpert Peter A, Ciuraru Raluca, Rossignol Stéphanie, Passananti Monica, Tinel Liselotte, Perrier Sebastien, Dupart Yoan, Steimer Sarah S, Ammann Markus, Donaldson D James, George Christian
Univ. Lyon, Université Claude Bernard Lyon 1, CNRS, UMR 5256, IRCELYON, Institut de recherches sur la catalyse et l'environnement de Lyon, 2 avenue Albert Einstein, F-69626, Villeurbanne, France.
Paul Scherrer Institute, Laboratory of Environmental Chemistry, 5232, Villigen, PSI, Switzerland.
Sci Rep. 2017 Oct 4;7(1):12693. doi: 10.1038/s41598-017-12601-2.
Organic interfaces that exist at the sea surface microlayer or as surfactant coatings on cloud droplets are highly concentrated and chemically distinct from the underlying bulk or overlying gas phase. Therefore, they may be potentially unique locations for chemical or photochemical reactions. Recently, photochemical production of volatile organic compounds (VOCs) was reported at a nonanoic acid interface however, subsequent secondary organic aerosol (SOA) particle production was incapable of being observed. We investigated SOA particle formation due to photochemical reactions occurring at an air-water interface in presence of model saturated long chain fatty acid and alcohol surfactants, nonanoic acid and nonanol, respectively. Ozonolysis of the gas phase photochemical products in the dark or under continued UV irradiation both resulted in nucleation and growth of SOA particles. Irradiation of nonanol did not yield detectable VOC or SOA production. Organic carbon functionalities of the SOA were probed using X-ray microspectroscopy and compared with other laboratory generated and field collected particles. Carbon-carbon double bonds were identified in the condensed phase which survived ozonolysis during new particle formation and growth. The implications of photochemical processes occurring at organic coated surfaces are discussed in the context of marine SOA particle atmospheric fluxes.
存在于海面微层或作为云滴表面活性剂涂层的有机界面高度浓缩,且在化学性质上与下层水体或上层气相不同。因此,它们可能是发生化学或光化学反应的潜在独特场所。最近,有人报道在壬酸界面发生了挥发性有机化合物(VOCs)的光化学生成,然而,随后未能观察到二次有机气溶胶(SOA)颗粒的生成。我们分别研究了在模型饱和长链脂肪酸和醇类表面活性剂壬酸和壬醇存在下,气 - 水界面发生的光化学反应导致的SOA颗粒形成。在黑暗中或持续紫外线照射下,气相光化学产物的臭氧分解均导致了SOA颗粒的成核和生长。照射壬醇未产生可检测到的VOC或SOA生成。使用X射线显微光谱法探测了SOA的有机碳官能团,并与其他实验室生成和现场采集的颗粒进行了比较。在新颗粒形成和生长过程中,在凝聚相中鉴定出了在臭氧分解过程中幸存的碳 - 碳双键。在海洋SOA颗粒大气通量的背景下,讨论了有机涂层表面发生的光化学过程的影响。