Isoprene suppression of new particle formation: Potential mechanisms and implications

Shan Hu Lee, Janek Uin, Alex B. Guenther, Joost A. de Gouw, Fangqun Yu, Alex B. Nadykto, Jason Herb, Nga L. Ng, Abigail Koss, William H. Brune, Karsten Baumann, Vijay P. Kanawade, Frank N. Keutsch, Athanasios Nenes, Kevin Olsen, Allen Goldstein, Qi Ouyang

Research output: Contribution to journalArticlepeer-review

24 Scopus citations

Abstract

Secondary aerosols formed from anthropogenic pollutants and natural emissions have substantial impacts on human health, air quality, and the Earth’s climate. New particle formation (NPF) contributes up to 70% of the global production of cloud condensation nuclei (CCN), but the effects of biogenic volatile organic compounds (BVOCs) and their oxidation products on NPF processes in forests are poorly understood. Observations show that isoprene, the most abundant BVOC, suppresses NPF in forests. But the previously proposed chemical mechanism underlying this suppression process contradicts atmospheric observations. By reviewing observations made in other forests, it is clear that NPF rarely takes place during the summer when emissions of isoprene are high, even though there are sufficient concentrations of monoterpenes. But at present it is not clear how isoprene and its oxidation products may change the oxidation chemistry of terpenes and how NOx and other atmospheric key species affect NPF in forest environments. Future laboratory experiments with chemical speciation of gas phase nucleation precursors and clusters and chemical composition of particles smaller than 10nm are required to understand the role of isoprene in NPF. Our results show that climate models can overpredict aerosol’s first indirect effect when not considering the absence of NPF in the southeastern U.S. forests during the summer using the current nucleation algorithm that includes only sulfuric acid and total concentrations of low-volatility organic compounds. This highlights the importance of understanding NPF processes as function of temperature, relative humidity, and BVOC compositions to make valid predictions of NPF and CCN at a wide range of atmospheric conditions.

Original languageEnglish (US)
Pages (from-to)14621-14635
Number of pages15
JournalJournal of Geophysical Research
Volume121
Issue number24
DOIs
StatePublished - Dec 27 2016

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

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