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PTR-MS measurements of concentrations and fluxes of biogenic VOCs in the humid tropics - rain forest vs. oil palm plantation

Misztal, Pawel K.; Langford, Ben; Di Marco, Chiara F.; Phillips, Gavin J.; Hewitt, Nick; Cape, J. Neil; Heal, Mathew R.; Nemitz, Eiko. 2009 PTR-MS measurements of concentrations and fluxes of biogenic VOCs in the humid tropics - rain forest vs. oil palm plantation. In: 4th International Conference on Proton Transfer Reaction Mass Spectrometry and its Applications, Obergurgl, Austria, 16 - 21 Feb 2009. Innsbruck, Austria, Innsbruck University Press, 120-124.

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Abstract/Summary

For the first time, concentrations and eddy covariance fluxes of several of the most abundant biogenic volatile organic compounds (VOCs) have been measured by PTR-MS in SE Asia (Malaysian Borneo) at two locations: at 75 m on a GAW tower over secondary rain forest and above an oil palm canopy. The operation of the instrument at both sites and the results are discussed in respect of the extremely high ambient humidity levels, which are not generally encountered outside of the humid tropics. Despite the challenging conditions, smooth operation could be achieved through instrument optimisation and anticondensation protection of the instrument set-up generally. The most abundant VOC was isoprene, with peak emissions of 4.7 mg m-2 h-1 above the rainforest and 30 mg m-2 h-1 above the oil palms. For most VOCs good sensitivities were obtained, but some of the strongly cluster-dependent OVOC species suffered a reduction in their detection limits. The results from both sites are presented, focussing on the effect of the different ambient humidity, which affected the normalised signal. At standard drift conditions the proton transfer reaction is known to dominate over the reaction with water clusters. However, at high humidities, water clusters appear to play a more significant role in the ultimate detection efficiencies. Nevertheless, PTR-MS has been proven to be capable of measuring various VOCs even in extreme tropical environments. In addition, some ideas for future instrument adjustments to facilitate tropical measurements are proposed.

Item Type: Publication - Conference Item (Paper)
Programmes: CEH Programmes pre-2009 publications > Biogeochemistry > BG01 Measuring and modelling trace gas, aerosol and carbon
CEH Sections: Billett (to November 2013)
Additional Keywords: Borneo, rainforest, oil palm plantation, VOCs, PTR-MS
NORA Subject Terms: Physics
Ecology and Environment
Chemistry
Atmospheric Sciences
Date made live: 07 Sep 2009 10:14
URI: http://nora.nerc.ac.uk/id/eprint/7965

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