Investigating the Aqueous Reaction of Vanillin with Nitrite under Dark Conditions - Kinetics and Brown Carbon Product Formation

FARIDEH HOSSEINI NAROUEI, Shiqi Ian Wang, Emily Baer, Juliana Marston, Hanie Tamandani, Yi Rao, V. Faye McNeill, Columbia University

     Abstract Number: 686
     Working Group: Aerosol Chemistry

Abstract
Phenols, produced during biomass burning, have been shown to form light-absorbing secondary organic material, or Brown Carbon (BrC), in the atmosphere. This study investigates the transformation of vanillin into BrC compounds in aqueous solutions containing sodium nitrite and sodium nitrate, mimicking tropospheric aerosol particles. While other studies report the formation of BrC under similar conditions but in the presence of UV light, our study focuses on dark conditions. A visible color change was observed on a timescale of minutes, corresponding to the development of an absorption peak at ~440 nm. BrC formation kinetics were characterized using UV-Vis spectrophotometry. The reaction mixture was characterized using UPLC-QToF-MS and products identified include nitrated dimers and higher order oligomers of vanillin and other nitrated aromatic species. The products and kinetics will be presented and the potential mechanism will be discussed. These findings provide critical insights into the formation of organonitrate and BrC products from methoxyphenols.