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Scientific Articles - PTR-MS Bibliography

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[1516] Misztal, P.. K., T.. Karl, R.. Weber, H.. H. Jonsson, A.. B. Guenther, and A.. H. Goldstein, "Airborne flux measurements of biogenic volatile organic compounds over California", Atmospheric Chemistry and Physics Discussions, vol. 14, pp. 7965–8013, Mar, 2014.
<p>Biogenic Volatile Organic Compound (BVOC) fluxes were measured onboard the CIRPAS Twin Otter aircraft as part of the California Airborne BVOC Emission Research in Natural Ecosystem Transects (CABERNET) campaign during June 2011. The airborne virtual disjunct eddy covariance (AvDEC) approach used measurements from a PTR-MS and a wind radome probe to directly determine fluxes of isoprene, MVK + MAC, methanol, monoterpenes, and MBO over 10 000 km of flight paths focusing on areas of California predicted to have the largest emissions of isoprene. The Fast Fourier Transform (FFT) approach was used to calculate fluxes over long transects of more than 15 km, most commonly between 50 and 150 km. The Continuous Wavelet Transformation (CWT) approach was used over the same transects to also calculate &quot;instantaneous&quot; fluxes with localization of both frequency and time independent of non-stationarities. Vertical flux divergence of isoprene is expected due to its relatively short lifetime and was measured directly using &quot;racetrack&quot; profiles at multiple altitudes. It was found to be linear and in the range 5% to 30% depending on the ratio of aircraft altitude to PBL height (z / zi). Fluxes were generally measured by flying consistently at 400 &plusmn; 50 m (a.g.l.) altitude, and extrapolated to the surface according to the determined flux divergence. The wavelet-derived surface fluxes of isoprene averaged to 2 km spatial resolution showed good correspondence to Basal Emission Factor (BEF) landcover datasets used to drive biogenic VOC (BVOC) emission models. The surface flux of isoprene was close to zero over Central Valley crops and desert shrublands, but was very high (up to 15 mg m&minus;2 h&minus;1) above oak woodlands, with clear dependence of emissions on temperature and oak density. Isoprene concentrations of up to 8 ppb were observed at aircraft height on the hottest days and over the dominant source regions. While isoprene emissions from agricultural crop regions, shrublands, and coniferous forests were extremely low, high concentrations of methanol and monoterpenes were found above some of these regions. These observations demonstrate the ability to measure fluxes from specific sources by eddy covariance from an aircraft, and suggest the utility of measurements using fast response chemical sensors to constrain emission inventories and map out source distributions for a much broader array of trace gases than was observed in this study. This paper reports the first regional direct eddy covariance fluxes of isoprene. The emissions of VOCs measured from aircraft with 2 km spatial resolution can quantify the distribution of major sources providing the observations required for testing statewide emission inventories of these important trace gases. These measurements will be used in a future study to assess BVOC emission models and their driving variable datasets.</p>
[1514] Karl, T.., P.. K. Misztal, H.. H. Jonsson, S.. Shertz, A.. H. Goldstein, and A.. B. Guenther, "Airborne Flux Measurements of BVOCs above Californian Oak Forests: Experimental Investigation of Surface and Entrainment Fluxes, OH Densities, and Damköhler Numbers", J. Atmos. Sci., vol. 70, pp. 3277–3287, Oct, 2013.
Link: et al 2013 JAS.pdf
<p>Airborne flux measurements of isoprene were performed over the Californian oak belts surrounding the Central Valley. The authors demonstrate for the first time 1) the feasibility of airborne eddy covariance measurements of reactive biogenic volatile organic compounds; 2) the effect of chemistry on the vertical transport of reactive species, such as isoprene; and 3) the applicability of wavelet analysis to estimate regional fluxes of biogenic volatile organic compounds. These flux measurements demonstrate that instrumentation operating at slower response times (e.g., 1&ndash;5 s) can still be used to determine eddy covariance fluxes in the mixed layer above land, where typical length scales of 0.5&ndash;3 km were observed. Flux divergence of isoprene measured in the planetary boundary layer (PBL) is indicative of OH densities in the range of 4&ndash;7 &times; 106 molecules per cubic centimeter and allows extrapolation of airborne fluxes to the surface with Damköhler numbers (ratio between the mixing time scale and the chemical time scale) in the range of 0.3&ndash;0.9. Most of the isoprene is oxidized in the PBL with entrainment fluxes of about 10% compared to the corresponding surface fluxes. Entrainment velocities of 1&ndash;10 cm s&minus;1 were measured. The authors present implications for parameterizing PBL schemes of reactive species in regional and global models.</p>
[1492] Misztal, P.. K., E.. Nemitz, B.. Langford, C.. F. Di Marco, G.. J. Phillips, C.. N. Hewitt, A.. R. MacKenzie, S.. M. Owen, D.. Fowler, M.. R. Heal, et al., "Direct ecosystem fluxes of volatile organic compounds from oil palms in South-East Asia", Atmospheric Chemistry and Physics, vol. 11, pp. 8995–9017, 2011.
<p>This paper reports the first direct eddy covariance fluxes of reactive biogenic volatile organic compounds (BVOCs) from oil palms to the atmosphere using proton-transfer-reaction mass spectrometry (PTR-MS), measured at a plantation in Malaysian Borneo. At midday, net isoprene flux constituted the largest fraction (84 %) of all emitted BVOCs measured, at up to 30 mg m&minus;2 h&minus;1 over 12 days. By contrast, the sum of its oxidation products methyl vinyl ketone (MVK) and methacrolein (MACR) exhibited clear deposition of 1 mg m&minus;2 h&minus;1, with a small average canopy resistance of 230 s m&minus;1. Approximately 15 % of the resolved BVOC flux from oil palm trees could be attributed to floral emissions, which are thought to be the largest reported biogenic source of estragole and possibly also toluene. Although on average the midday volume mixing ratio of estragole exceeded that of toluene by almost a factor of two, the corresponding fluxes of these two compounds were nearly the same, amounting to 0.81 and 0.76 mg m&minus;2 h&minus;1, respectively. By fitting the canopy temperature and PAR response of the MEGAN emissions algorithm for isoprene and other emitted BVOCs a basal emission rate of isoprene of 7.8 mg m&minus;2 h&minus;1 was derived. We parameterise fluxes of depositing compounds using a resistance approach using direct canopy measurements of deposition. Consistent with Karl et al. (2010), we also propose that it is important to include deposition in flux models, especially for secondary oxidation products, in order to improve flux predictions.</p>
[1491] Hewitt, C.. N., K.. Ashworth, A.. Boynard, A.. Guenther, B.. Langford, A.. R. MacKenzie, P.. K. Misztal, E.. Nemitz, S.. M. Owen, M.. Possell, et al., "Ground-level ozone influenced by circadian control of isoprene emissions", Nature Geoscience, vol. 4, pp. 671–674, 2011.
<p>The volatile organic compound isoprene is produced by many plant species, and provides protection against biotic and abiotic stresses1. Globally, isoprene emissions from plants are estimated to far exceed anthropogenic emissions of volatile organic compounds2. Once in the atmosphere, isoprene reacts rapidly with hydroxyl radicals3 to form peroxy radicals, which can react with nitrogen oxides to form ground-level ozone4. Here, we use canopy-scale measurements of isoprene fluxes from two tropical ecosystems in Malaysia&mdash;a rainforest and an oil palm plantation&mdash;and three models of atmospheric chemistry to explore the effects of isoprene fluxes on ground-level ozone. We show that isoprene emissions in these ecosystems are under circadian control on the canopy scale, particularly in the oil palm plantation. As a result, these ecosystems emit less isoprene than present emissions models predict. Using local-, regional- and global-scale models of atmospheric chemistry and transport, we show that accounting for circadian control of isoprene emissions brings model predictions of ground-level ozone into better agreement with measurements, especially in isoprene-sensitive regions of the world.</p>
[1493] Langford, B.., P.. K. Misztal, E.. Nemitz, B.. Davison, C.. Helfter, T.. A. M. Pugh, A.. R. MacKenzie, S.. F. Lim, and C.. N. Hewitt, "Fluxes and concentrations of volatile organic compounds from a South-East Asian tropical rainforest", Atmospheric Chemistry and Physics, vol. 10, pp. 8391–8412, 2010.
<p>As part of the OP3 field study of rainforest atmospheric chemistry, above-canopy fluxes of isoprene, monoterpenes and oxygenated volatile organic compounds were made by virtual disjunct eddy covariance from a South-East Asian tropical rainforest in Malaysia. Approximately 500 hours of flux data were collected over 48 days in April&ndash;May and June&ndash;July 2008. Isoprene was the dominant non-methane hydrocarbon emitted from the forest, accounting for 80% (as carbon) of the measured emission of reactive carbon fluxes. Total monoterpene emissions accounted for 18% of the measured reactive carbon flux. There was no evidence for nocturnal monoterpene emissions and during the day their flux rate was dependent on both light and temperature. The oxygenated compounds, including methanol, acetone and acetaldehyde, contributed less than 2% of the total measured reactive carbon flux. The sum of the VOC fluxes measured represents a 0.4% loss of daytime assimilated carbon by the canopy, but atmospheric chemistry box modelling suggests that most (90%) of this reactive carbon is returned back to the canopy by wet and dry deposition following chemical transformation. The emission rates of isoprene and monoterpenes, normalised to 30 &deg;C and 1000 μmol m&minus;2 s&minus;1 PAR, were 1.6 mg m&minus;2 h&minus;1 and 0.46mg m&minus;2 h&minus;1 respectively, which was 4 and 1.8 times lower respectively than the default value for tropical forests in the widely-used MEGAN model of biogenic VOC emissions. This highlights the need for more direct canopy-scale flux measurements of VOCs from the world&#39;s tropical forests.</p>

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Selected PTR-MS related Reviews

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).

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.

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.


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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