A31F-04
Development and field deployment of an instrument to measure ozone production rates in the troposphere

Wednesday, 16 December 2015: 08:45
3004 (Moscone West)
Sofia Sklaveniti1,2, Nadine Locoge1, Sebastien Dusanter1,2, Thierry Leonardis1, Michelle Lew3, Brandon Bottorff3, Pamela Sue Rickly Sigler2, Philip S Stevens4, Ezra C D Wood5, Shuvashish Kundu6 and Drew R Gentner7, (1)Mines Douai, Atmospheric Sciences and Environmental Engineering (SAGE), F-59508 Douai, France, (2)School of Public and Environmental Affairs, Indiana University, Bloomington, IN, United States, (3)Indiana University Bloomington, Chemistry, Bloomington, IN, United States, (4)Indiana Univ, Bloomington, IN, United States, (5)U. of Massachusetts - Amherst, Amherst, MA, United States, (6)University of Iowa, Iowa City, IA, United States, (7)Yale University, Chemical & Environmental Engineering, New Haven, CT, United States
Abstract:
Ozone is a greenhouse gas and a primary constituent of urban smog, irritating the respiratory system and damaging the vegetation. The current understanding of ozone chemistry in the troposphere indicates that net ozone production P(O3) occurs when peroxy radicals (HO2+RO2) react with NO producing NO2, whose photolysis leads to O3 formation. P(O3) values can be calculated from peroxy radical concentrations, either from ambient measurements or box model outputs. These two estimation methods often disagree for NOx mixing ratios higher than a few ppb, questioning our ability to measure peroxy radicals under high NOx conditions or indicating that there are still unknowns in our understanding of the radical and ozone production chemistry. Direct measurements of ozone production rates will help to address this issue and improve air quality regulations.

We will present the development of an instrument for direct measurements of ozone production rates (OPR). The OPR instrument consists of three parts: (i) two quartz flow tubes sampling ambient air (“Ambient” and “Reference” flow tube), (ii) an O3-to-NO2 conversion unit, and (iii) a Cavity Attenuated Phase Shift (CAPS) monitor to measure NO2. The air in the Ambient flow tube undergoes the same photochemistry as in ambient air, while the Reference flow tube is covered by a UV filter limiting the formation of ozone. Exiting the flow tubes, ozone is converted into NO2 and the sum O3+NO2 (Ox) is measured by the CAPS monitor. The difference in Ox between the two flow tubes divided by the residence time yields the Ox production rate, P(Ox). P(O3) is assumed to be equal to P(Ox) when NO2 is efficiently photolyzed during daytime. We will present preliminary results from the Indiana Radical, Reactivity and Ozone Production Intercomparison (IRRONIC) campaign in Bloomington, Indiana, during July 2015, where ozone production rates were measured by introducing various amounts of NO inside the flow tubes to investigate the ozone production sensitivity.

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