ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-12-10125-2012 Contributions of individual reactive biogenic volatile organic compounds to organic nitrates above a mixed forest Pratt K. A. 1 Mielke L. H. 1 11 Shepson P. B. 1 2 3 Bryan A. M. 4 Steiner A. L. 4 Ortega J. 5 12 Daly R. 5 13 Helmig D. 5 Vogel C. S. 6 Griffith S. 7 Dusanter S. 7 8 9 Stevens P. S. 7 10 Alaghmand M. 1 Department of Chemistry, Purdue University, West Lafayette, IN, USA Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN, USA Purdue Climate Change Research Center, Purdue University, West Lafayette, IN, USA Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, MI, USA Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO, USA University of Michigan Biological Station, Pellston, MI, USA School of Public and Environmental Affairs, Indiana University, Bloomington, IN, USA Université Lille Nord de France, Lille, France École des Mines de Douai, Douai, France Department of Chemistry, Indiana University, Bloomington, IN, USA now at: School of Public and Environmental Affairs, Indiana University, Bloomington, IN, USA now at: Atmospheric Chemistry Division, Earth System Laboratory, National Center for Atmospheric Research, Boulder, CO, USA now at: Air Pollution Prevention and Control Division, National Risk Management Research Laboratory, US Environmental Protection Agency, Research Triangle Park, NC, USA 05 11 2012 12 21 10125 10143 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/12/10125/2012/acp-12-10125-2012.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/12/10125/2012/acp-12-10125-2012.pdf

Biogenic volatile organic compounds (BVOCs) can react in the atmosphere to form organic nitrates, which serve as NO<sub>x</sub> (NO + NO<sub>2</sub>) reservoirs, impacting ozone and secondary organic aerosol production, the oxidative capacity of the atmosphere, and nitrogen availability to ecosystems. To examine the contributions of biogenic emissions and the formation and fate of organic nitrates in a forest environment, we simulated the oxidation of 57 individual BVOCs emitted from a rural mixed forest in northern Michigan. Key BVOC-oxidant reactions were identified for future laboratory and field investigations into reaction rate constants, yields, and speciation of oxidation products. Of the total simulated organic nitrates, monoterpenes contributed ~70% in the early morning at ~12 m above the forest canopy when isoprene emissions were low. In the afternoon, when vertical mixing and isoprene nitrate production were highest, the simulated contribution of isoprene-derived organic nitrates was greater than 90% at all altitudes, with the concentration of secondary isoprene nitrates increasing with altitude. Notably, reaction of isoprene with NO<sub>3</sub> leading to isoprene nitrate formation was found to be significant (~8% of primary organic nitrate production) during the daytime, and monoterpene reactions with NO<sub>3</sub> were simulated to comprise up to ~83% of primary organic nitrate production at night. Lastly, forest succession, wherein aspen trees are being replaced by pine and maple trees, was predicted to lead to increased afternoon concentrations of monoterpene-derived organic nitrates. This further underscores the need to understand the formation and fate of these species, which have different chemical pathways and oxidation products compared to isoprene-derived organic nitrates and can lead to secondary organic aerosol formation.

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