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Scientific Articles - PTR-MS Bibliography

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Found 4 results
Title [ Year(Asc)]
Filters: Author is Langford, B.  [Clear All Filters]
[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>
[1494] Hewitt, C.. N., A.. R. MacKenzie, P.. Di Carlo, C.. F. Di Marco, J.. R. Dorsey, M.. Evans, D.. Fowler, M.. W. Gallagher, J.. R. Hopkins, C.. E. Jones, et al., "Nitrogen management is essential to prevent tropical oil palm plantations from causing ground-level ozone pollution", Proceedings of the National Academy of Sciences, 2009.
<p>More than half the world&#39;s rainforest has been lost to agriculture since the Industrial Revolution. Among the most widespread tropical crops is oil palm (Elaeis guineensis): global production now exceeds 35 million tonnes per year. In Malaysia, for example, 13% of land area is now oil palm plantation, compared with 1% in 1974. There are enormous pressures to increase palm oil production for food, domestic products, and, especially, biofuels. Greater use of palm oil for biofuel production is predicated on the assumption that palm oil is an &ldquo;environmentally friendly&rdquo; fuel feedstock. Here we show, using measurements and models, that oil palm plantations in Malaysia directly emit more oxides of nitrogen and volatile organic compounds than rainforest. These compounds lead to the production of ground-level ozone (O3), an air pollutant that damages human health, plants, and materials, reduces crop productivity, and has effects on the Earth&#39;s climate. Our measurements show that, at present, O3 concentrations do not differ significantly over rainforest and adjacent oil palm plantation landscapes. However, our model calculations predict that if concentrations of oxides of nitrogen in Borneo are allowed to reach those currently seen over rural North America and Europe, ground-level O3 concentrations will reach 100 parts per billion (109) volume (ppbv) and exceed levels known to be harmful to human health. Our study provides an early warning of the urgent need to develop policies that manage nitrogen emissions if the detrimental effects of palm oil production on air quality and climate are to be avoided.</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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