Statistical Distributions and the Multigenerational Oxidation of Organic Aerosol

A key challenge is to develop robust general theories or parameterizations of aerosol formation and aging that can accurately describe the multigenerational oxidation of hundreds if not thousands of distinct molecular species found in ambient aerosols.  Such parameterizations include a number of recently-developed “reduced” variable representations of organic aerosol formation and aging, which are based upon measureable average bulk aerosol properties, such as elemental ratios (O/C and H/C), carbon oxidation state, polarity, volatility, or electron ionization marker ions to represent how oxidation changes organic aerosol composition. We are developing a conceptual framework that broadly explains oxidation chemistry as “trajectories” through of bulk aerosol properties (e.g. mass, elemental composition) through these reduced variable spaces, by considering the formation, evolution and volatilization of individual generations of oxidation products. This conceptual framework considers oxidation as a complex vector or “trajectory” in carbon oxidation state vs. carbon number space (shown below). These results reveal more broadly the importance of developing statistical approaches for explaining complex chemical phenomena to more accurately predict bulk aerosol properties such as volatility and hygroscopicity.