| Title: | Protonation and oligomerization of gaseous isoprene on mildly acidic surfaces: implications for atmospheric chemistry |
| Author(s): | Enami S; Mishra H; Hoffmann MR; Colussi AJ; |
| Address: | "Ronald and Maxine Linde Center for Global Environmental Science, California Institute of Technology, Pasadena, California 91125, United States" |
| ISSN/ISBN: | 1520-5215 (Electronic) 1089-5639 (Linking) |
| Abstract: | "In a global process linking the Earth's climate with its ecosystems, massive photosynthetic isoprene (ISOP) emissions are converted to light-scattering haze. This phenomenon is imperfectly captured by atmospheric chemistry models: predicted ISOP emissions atop forest canopies would deplete the oxidizing capacity of the overhead atmosphere, at variance with field observations. Here we address this key issue in novel laboratory experiments where we apply electrospray mass spectrometry to detect online the products of the reactive uptake of gaseous ISOP on the surface of aqueous jets as a function of acidity. We found that ISOP is already protonated to ISOPH(+) and undergoes cationic oligomerization to (ISOP)(2)H(+) and (ISOP)(3)H(+) on the surface of pH < 4 water jets. We estimate uptake coefficients, gamma(ISOP) = (0.5 - 2.0) x 10(-6) on pH = 3 water, which translate into the significant reuptake of leaf-level ISOP emissions in typical (surface-to-volume approximately 5 m(-1)) forests during realistic (a few minutes) in-canopy residence times. Our findings may also account for the rapid decay of ISOP in forests after sunset and help bring the global budget of volatile organic compounds closer to balance" |
| Keywords: | "Atmosphere/*chemistry Butadienes/*chemistry Carboxylic Acids/*chemistry Gases/chemistry Hemiterpenes/*chemistry Pentanes/*chemistry Protons Spectrometry, Mass, Electrospray Ionization Surface Properties;" |
| Notes: | "MedlineEnami, Shinichi Mishra, Himanshu Hoffmann, Michael R Colussi, Agustin J eng Research Support, U.S. Gov't, Non-P.H.S. 2012/02/24 J Phys Chem A. 2012 Jun 21; 116(24):6027-32. doi: 10.1021/jp2110133. Epub 2012 Feb 22" |
