|Title||The old and the new: Aging of sea spray aerosol and formation of secondary marine aerosol through OH oxidation reactions|
|Publication Type||Journal Article|
|Year of Publication||2019|
|Authors||Trueblood J.V, Wang X.F, Or V.W, Alves M.R, Santander M.V, Prather KA, Grassian VH|
|Type of Article||Article|
|Keywords||aerosol mass spectrometry; alkanes; ammonia; Atomic force; chemistry; Geochemistry & Geophysics; heterogeneous oxidation; hydroxyl radicals; kinetics; microscopy-photothermal infrared spectroscopy; particles; pathways; phytoplankton; products; reaction; single particle analysis; state; sulfate|
In this study, we have investigated the effect of hydroxyl radical (OH) oxidation reactions on the formation and chemical composition of marine-derived aerosols. Marine aerosols can be classified into two categories: primary sea spray aerosol (SSA) produced upon the breaking of waves, and secondary marine aerosol (SMA) produced upon the oxidation of gas phase species. Here we simultaneously investigated the impact of heterogeneous OH oxidation reactions on chemically complex supermicron SSA as well as the formation of SMA in the submicron regime through the oxidation of volatile organic compounds (VOCs). A marine aerosol reference tank (MART) filled with water from a labgrown phytoplankton bloom was used to produce SSA particles and VOCs representative of those found over the ocean, which were then sent through a potential aerosol mass (PAM) reactor where they were exposed to OH radicals. Online and offline methods were used to compare unreacted nascent primary SSA to the marine aerosols that resulted from sending the MART headspace, which includes any gases and existing primary SSA, through the PAM. Several single particle methods of analysis, including micro-Raman spectroscopy and atomic force microscopy-photothermal infrared (AFM-PTIR) spectroscopy, were used to investigate composition and size of substrate deposited particles. In situ composition measurements of PM1 particles were made using an aerosol mass spectrometer (AMS) to understand submicron marine aerosol chemistry. Raman spectra of SSA showed that heterogeneous OH oxidation reactions significantly lower the amount of organic matter found in supermicron SSA particles, which are dominated, in part, by nitrogen containing species (e.g., amino sugars/amino acids) during periods of high biological productivity. Furthermore, AFM and AMS analyses showed the formation of secondary marine aerosols in the submicron size regime due to oxidation of biologically produced VOCs. To our knowledge, this is the first study in which lab-produced authentic marine aerosols produced during a phytoplankton bloom have been exposed to OH radicals. The results provide important insights to how the combined effects of ocean biological activity and OH oxidation reactions both ultimately play roles in determining the chemical composition of marine aerosols (SMA and SSA) across multiple size regimes and formation mechanisms.