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Scientific Articles - PTR-MS Bibliography

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Found 2 results
Title [ Year(Desc)]
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Filters: Author is Potosnak, Mark  [Reset Search]
2004
[Karl2004] Karl, T., M. Potosnak, A. Guenther, D. Clark, J. Walker, J. D. Herrick, and C. Geron, "Exchange processes of volatile organic compounds above a tropical rain forest: Implications for modeling tropospheric chemistry above dense vegetation", Journal of geophysical research, vol. 109, no. D18: American Geophysical Union, pp. D18306, 2004.
Link: http://www.agu.org/pubs/crossref/2004/2004JD004738.shtml
Abstract
Disjunct eddy covariance in conjunction with continuous in-canopy gradient measurements allowed for the first time to quantify the fine-scale source and sink distribution of some of the most abundant biogenic (isoprene, monoterpenes, methanol, acetaldehyde, and acetone) and photooxidized (MVK+MAC, acetone, acetaldehyde, acetic, and formic acid) VOCs in an old growth tropical rain forest. Our measurements revealed substantial isoprene emissions (up to 2.50 mg m−2 h−1) and light-dependent monoterpene emissions (up to 0.33 mg m−2 h−1) at the peak of the dry season (April and May 2003). Oxygenated species such as methanol, acetone, and acetaldehyde were typically emitted during daytime with net fluxes up to 0.50, 0.36, and 0.20 mg m−2 h−1, respectively. When generalized for tropical rain forests, these fluxes would add up to a total emission of 36, 16, 19, 106, and 7.2 Tg/yr for methanol, acetaldehyde, acetone, isoprene, and monoterpenes, respectively. During nighttime we observed strong sinks for oxygenated and nitrogen-containing compounds such as methanol, acetone, acetaldehyde, MVK+MAC, and acetonitrile with deposition velocities close to the aerodynamic limit. This suggests that the canopy resistance (Rc) is very small and not the rate-limiting step for the nighttime deposition of many VOCs. Our measured mean dry deposition velocities of methanol, acetone, acetaldehyde, MVK+MAC, and acetonitrile were a factor 10–20 higher than estimated from traditional deposition models. If our measurements are generalized, this could have important implications for the redistribution of VOCs in atmospheric chemistry models. Our observations indicate that the current understanding of reactive carbon exchange can only be seen as a first-order approximation.
2007
[1488] Karl, T., A. Guenther, R. J. Yokelson, J. Greenberg, M. Potosnak, D. R. Blake, and P. Artaxo, "The tropical forest and fire emissions experiment: Emission, chemistry, and transport of biogenic volatile organic compounds in the lower atmosphere over Amazonia", Journal of Geophysical Research: Atmospheres, vol. 112, pp. n/a–n/a, 2007.
Link: http://dx.doi.org/10.1029/2007JD008539
Abstract
<p>Airborne and ground-based mixing ratio and flux measurements using eddy covariance (EC) and for the first time the mixed layer gradient (MLG) and mixed layer variance (MLV) techniques are used to assess the impact of isoprene and monoterpene emissions on atmospheric chemistry in the Amazon basin. Average noon isoprene (7.8 &plusmn; 2.3 mg/m2/h) and monoterpene fluxes (1.2 &plusmn; 0.5 mg/m2/h) compared well between ground and airborne measurements and are higher than fluxes estimated in this region during other seasons. The biogenic emission model, Model of Emissions of Gases and Aerosols from Nature (MEGAN), estimates fluxes that are within the model and measurement uncertainty and can describe the large observed variations associated with land-use change in the region north-west of Manaus. Isoprene and monoterpenes accounted for &sim;75% of the total OH reactivity in this region and are important volatile organic compounds (VOCs) for modeling atmospheric chemistry in Amazonia. The presence of fair weather clouds (cumulus humilis) had an important impact on the vertical distribution and chemistry of VOCs through the planetary boundary layer (PBL), the cloud layer, and the free troposphere (FT). Entrainment velocities between 10:00 and 11:30 local time (LT) are calculated to be on the order of 8&ndash;10 cm/s. The ratio of methyl-vinyl-ketone (MVK) and methacrolein (MAC) (unique oxidation products of isoprene chemistry) with respect to isoprene showed a pronounced increase in the cloud layer due to entrainment and an increased oxidative capacity in broken cloud decks. A decrease of the ratio in the lower free troposphere suggests cloud venting through activated clouds. OH modeled in the planetary boundary layer using a photochemical box model is much lower than OH calculated from a mixed layer budget approach. An ambient reactive sesquiterpene mixing ratio of 1% of isoprene would be sufficient to explain most of this discrepancy. Increased OH production due to increased photolysis in the cloud layer balances the low OH values modeled for the planetary boundary layer. The intensity of segregation (Is) of isoprene and OH, defined as a relative reduction of the reaction rate constant due to incomplete mixing, is found to be significant: up to 39 &plusmn; 7% in the &sim;800-m-deep cloud layer. The effective reaction rate between isoprene and OH can therefore vary significantly in certain parts of the lower atmosphere.</p>

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F. Biasioli, C. Yeretzian, F. Gasperi, T. D. Märk: PTR-MS monitoring of VOCs and BVOCs in food science and technology, Trends in Analytical Chemistry 30 (7) (2011).
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J. de Gouw, C. Warneke, T. Karl, G. Eerdekens, C. van der Veen, R. Fall: Measurement of Volatile Organic Compounds in the Earth's Atmosphere using Proton-Transfer-Reaction Mass Spectrometry. Mass Spectrometry Reviews, 26 (2007), 223-257.
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W. Lindinger, A. Hansel, A. Jordan: Proton-transfer-reaction mass spectrometry (PTR–MS): on-line monitoring of volatile organic compounds at pptv levels, Chem. Soc. Rev. 27 (1998), 347-375.
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Lists with PTR-MS relevant publications of the University of Innsbruck can be found here: Atmospheric and indoor air chemistry, IMR, Environmental Physics and Nano-Bio-Physics

 

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