Secondary formation of nitrophenols in an oil and gas production region: insights from observations during the Uintah Basin Winter Ozone Study (UBWOS) 2014

Monday, 15 December 2014
Bin Yuan1,2, John Liggio3, Jeremy J B Wentzell4, Shao-Meng Li5, Harald Stark6, Hans Dieter Osthoff7, James M Roberts8, Jessica Gilman9, Brian M Lerner10, Rui Li11, Amy Leithead3, Patrick R Veres11, Carsten Warneke11, Robert J Wild12, Steven S Brown13 and Joost A De Gouw1, (1)NOAA Earth System Research Lab, Boulder, CO, United States, (2)Cooperative Institute for Research in Environmental Sciences, Boulder, CO, United States, (3)Air Quality Research Division, Toronto, ON, Canada, (4)Environment Canada Dorval, Toronto, ON, Canada, (5)Environment Canada, Toronto, ON, Canada, (6)University of Colorado at Boulder, Boulder, CO, United States, (7)University of Calgary, Chemistry, Calgary, AB, Canada, (8)NOAA/ESRL, Boulder, CO, United States, (9)NOAA ESRL, Boulder, CO, United States, (10)NOAA, Earth System Research La, Boulder, CO, United States, (11)NOAA Boulder, Boulder, CO, United States, (12)Colorado University/NOAA/ESRL, Boulder, CO, United States, (13)NOAA Earth System Research Lab, Chemical Sciences Division, Boulder, CO, United States
Nitrophenols play important roles in the atmosphere, for example as light-absorbing organic matter, phytotoxins, precursors of secondary organic aerosol (SOA) and HONO. Besides emissions from primary sources, nitrophenols are important secondary products from the oxidation of aromatics in the atmosphere. Nitrophenols were measured along with many other organic acids using an acetate ion (CH3COO-) time of flight chemical ionization mass spectrometer (TOF-CIMS) at a site in an oil and gas producing region during Uintah Basin Winter Ozone Study (UBWOS) in 2014. Nitrophenol and methyl-substituted nitrophenols exhibited distinct diurnal profiles, with high concentrations at night and a minimum observed during the daytime. This is consistent with photolysis being the dominant sink of these species. For this study, nitrophenols are most likely formed in situ, while primary emissions (e.g. biomass burning, oil and gas emissions) are negligible during this campaign. We will quantify the contributions of gas phase reactions of phenols with OH and NO3 radicals to form nitrophenols. The importance of heterogeneous reactions resulting for nitrophenol formation, including N2O5 chemistry on surfaces and photolysis of nitrate in the snow will be also explored using vertical gradient measurements at two different heights (1.0 m and 18.5 m). In contrast with mono-nitrophenols, dinitrophenol showed a daytime maximum, indicating that the formation of dinitrophenol is driven by photochemistry in the atmosphere. The results of this study will be helpful to improving our understanding the budget of nitrophenols and oxidation mechanisms of aromatics in the atmosphere.