Novel Analysis to Quantify Plume Crosswind Heterogeneity Applied to Biomass...

Decker, Z., S. Wang, I. Bourgeois, P. Campuzano-Jost, M. Coggon, J. P. DiGangi, G. S. Diskin, F. Flocke, A. Franchin, C. Fredrickson, G. Gkatzelis, S. R. Hall, H. Halliday, K. Hayden, C. D. Holmes, L. G. Huey, J. L. Jimenez, Y. R. Lee, J. Lindaas, A. Middlebrook, D. D. Montzka, J. A. Neuman, J. B. Nowak, D. Pagonis, B. B. Palm, J. Peischl, F. Piel, P. Rickly, M. Robinson, A. Rollins, T. B. Ryerson, K. Sekimoto, J. Thornton, G. Tyndall, K. Ullmann, P. Veres, C. Warneke, R. Washenfelder, A. Weinheimer, A. Wisthaler, C. Womack, and S. S. Brown (2021), Novel Analysis to Quantify Plume Crosswind Heterogeneity Applied to Biomass Burning Smoke, Environ. Sci. Technol., 55, 15646-15657, doi:10.1021/acs.est.1c03803.

We present a novel method, the Gaussian observational model for edge to center heterogeneity (GOMECH), to quantify the horizontal chemical structure of plumes. GOMECH fits observations of short-lived emissions or products against a long-lived tracer (e.g., CO) to provide relative metrics for the plume width (wi/wCO) and center (bi/wCO). To validate GOMECH, we investigate OH and NO3 oxidation processes in smoke plumes sampled during FIREX-AQ (Fire Influence on Regional to Global Environments and Air Quality, a 2019 wildfire smoke study). An analysis of 430 crosswind transects demonstrates that nitrous acid (HONO), a primary source of OH, is narrower than CO (wHONO/wCO = 0.73−0.84 ± 0.01) and maleic anhydride (an OH oxidation product) is enhanced on plume edges (wmaleicanhydride/wCO = 1.06−1.12 ± 0.01). By contrast, NO3 production [P(NO3)] occurs mainly at the plume center (wP(NO3)/wCO = 0.91−1.00 ± 0.01). Phenolic emissions, highly reactive to OH and NO3, are narrower than CO (wphenol/wCO = 0.96 ± 0.03, wcatechol/wCO = 0.91 ± 0.01, and wmethylcatechol/wCO = 0.84 ± 0.01), suggesting that plume edge phenolic losses are the greatest. Yet, nitrophenolic aerosol, their oxidation product, is the greatest at the plume center (wnitrophenolicaerosol/wCO = 0.95 ± 0.02). In a large plume case study, GOMECH suggests that nitrocatechol aerosol is most associated with P(NO3). Last, we corroborate GOMECH with a large eddy simulation model which suggests most (55%) of nitrocatechol is produced through NO3 in our case study.

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Tropospheric Composition Program (TCP)