Nocturnal NO3 radical chemistry in Houston,TX |
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| Authors: | Jochen Stutz Kam Weng Wong Laura Lawrence Luke Ziemba James H Flynn Bernhard Rappenglück Barry Lefer |
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| Institution: | 1. School of Energy and Power Engineering, University of Shanghai for Science and Technology, Shanghai, China;2. Department of Physics, National Institute of Technology Calicut, Calicut 673601, Kerala, India;3. Physics Department & Environmental Research Institute, University College Cork, Cork, Ireland;4. Optind Solutions Pvt. LTD. Unit 11, Technology Business Incubator, National Institute of Technology Calicut, Calicut 673601, Kerala, India;5. School of Chemistry & Environmental Research Institute, University College Cork, Cork, Ireland;1. Department of Atmospheric Sciences, Pusan National University, Busan 609-735, Republic of Korea;2. Air Quality Forecasting Center, Climate and Air Quality Research Department, National Institute of Environmental Research, Incheon 22689, Republic of Korea;1. Centre National de la Recherche Scientifique (CNRS) (UPR 3021), Observatoire des Sciences de l''Univers en région Centre (OSUC), Institut de Combustion, Aérothermique, Réactivité et Environnement (ICARE), Orléans 45071, France;2. Earth Sciences Department, Scientific Institute, Mohammed V University, Rabat 10106, Morocco;3. Le Studium Loire Valley Institute for Advanced Studies, Orléans 45071, France |
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| Abstract: | Radical chemistry in the nocturnal urban boundary layer is dominated by the nitrate radical, NO3, which oxidizes hydrocarbons and, through the aerosol uptake of N2O5, indirectly influences the nitrogen budget. The impact of NO3 chemistry on polluted atmospheres and urban air quality is, however, not well understood, due to a lack of observations and the strong impact of vertical stability of the boundary layer, which makes nocturnal chemistry highly altitude dependent.Here we present long-path DOAS observations of the vertical distribution of the key nocturnal species O3, NO2, and NO3 during the TRAMP experiment in Summer 2006 in Houston, TX. Our observations confirm the altitude dependence of nocturnal chemistry, which is reflected in the concentration profiles of all trace gases at night. In contrast to other study locations, NO3 chemistry in Houston is dominated by industrial emissions of alkenes, in particular of isoprene, isobutene, and sporadically 1,3-butadiene, which are responsible for more than 70% of the nocturnal NO3 loss. The nocturnally averaged loss of NOx in the lowest 300 m of the Houston atmosphere is ～0.9 ppb h?1, with little day-to-day variability. A comparison with the daytime NOx loss shows that NO3 chemistry is responsible for 16–50% of the NOx loss in a 24-h period in the lowest 300 m of the atmosphere. The importance of the NO3 + isoprene/1,3-butadiene reactions implies the efficient formation of organic nitrates and secondary organic aerosol at night in Houston. |
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