Journal of Atmospheric Chemistry

, Volume 72, Issue 3–4, pp 215–234 | Cite as

Nocturnal isoprene declines in a semi-urban environment

  • David Doughty
  • Jose D. Fuentes
  • Ricardo Sakai
  • Xiao-Ming Hu
  • Kevin Sanchez


In environments dominated by biogenic hydrocarbon emissions, the transition from daytime to nighttime is an important period because ambient isoprene levels rapidly decrease. In sub-urban environments with abundant sources of nitrogen oxides, the nighttime isoprene chemistry has implications for the regional nitrogen oxide budget. Given the substantial production of alkyl nitrates from isoprene reactions during the nighttime, nitrogen oxides can then be transported long distances in the form of nitrates. The factors that influence nighttime chemistry of isoprene in environments with abundant sources of nitrogen oxides are not well known. Therefore, the objective of this study was to understand the processes controlling isoprene levels just before and after sunset, in an environment under the influences of moderate concentrations of ambient nitrogen oxides. Utilizing in-situ Proton-Transfer-Reaction Mass Spectrometer measurements, isoprene levels were studied during July to August 2011 in a sub-urban environment outside the metropolis of Washington, D.C., USA. Numerical modeling investigations were also pursued to determine yields of alkyl nitrates. Pre-sunset isoprene rises, observed on eight measured days, were likely related to the cessation of atmospheric turbulence and stabilization of the surface layer. After sunset, nocturnal declines of isoprene, while not fully explained by chemical reactions, depended on the amounts of nitrate radicals in the lower atmosphere. Furthermore, isoprene destruction rates and associated production of alkyl nitrates depended on the amounts of nitrogen oxides. Compared with cases with ambient nitrogen oxides lower than 10 parts per billion, model results showed that twice the amounts of isoprene were destroyed when average nitrogen oxide levels exceeded 30 parts per billion.


Biogenic VOC Air Pollution Alkyl Nitrates Isoprene Emission 



The National Atmospheric and Space Administration, NASA, provided funding for this research (grant NNX08BA42A). We are indebted to the colleagues at the Howard University Beltsville Campus for their hospitality during the 2011 summer measurements. We thank Eugen Hartgen for his assistance with PTR-MS operations during the summer, 2011, as well as Danny Wang for providing the gas standards and analyzing the canister samples for volatile organic compounds. We are indebted to Armin Wisthaler and Alfons Jordan for providing timely help with the analysis of the PTR-MS data. Two anonymous reviewers provided comments that resulted in a much improved manuscript.

Supplementary material

10874_2012_9247_MOESM1_ESM.docx (69 kb)
ESM 1 (DOCX 68.5kb)


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Copyright information

© Springer Science+Business Media Dordrecht 2013

Authors and Affiliations

  • David Doughty
    • 1
  • Jose D. Fuentes
    • 1
  • Ricardo Sakai
    • 2
  • Xiao-Ming Hu
    • 3
  • Kevin Sanchez
    • 1
  1. 1.Department of MeteorologyThe Pennsylvania State UniversityUniversity ParkUSA
  2. 2.Department of PhysicsHoward UniversityWashingtonUSA
  3. 3.Center for Analysis and Prediction of StormsUniversity of OklahomaNormanUSA

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