Emerging investigator series: heterogeneous OH oxidation of primary brown carbon aerosol: effects of relative humidity and volatility
Elijah G. Schnitzler, Tengyu Liu, Rachel F. Hems, Jonathan P. D. Abbatt
Abstract
(associated with carboxylic acids), the O : C ratio, and the carbon oxidation state, consistent with extensive functionalization. These composition changes corresponded first to very rapid absorption enhancement and then bleaching. Net bleaching was observed after the equivalent of 10 h residence time in the atmosphere. The evolution did not depend strongly on RH, consistent with homogeneously well-mixed primary BrC even at 15% RH at room temperature. In contrast, the evolution did depend strongly on the pre-treatment of the particles, such that only bleaching occurred for particles treated at 200 °C. This suggests that lower volatility constituents of ambient primary BrC have less capacity for absorption enhancement in the atmosphere upon heterogeneous oxidation, potentially as they are already more functionalized and/or oligomeric.