Fluxes and In-Canopy Gradients of Biogenic Volatile Organic Compounds Above Contrasting South East Asian Land Uses

Nemitz, E.; Misztal, P.; Langford, B.; Oram, D.; Phillips, G.; Di Marco, C.; Davison, B.; Hewitt, N.; Cape, N.. 2008 Fluxes and In-Canopy Gradients of Biogenic Volatile Organic Compounds Above Contrasting South East Asian Land Uses. Eos Trans. AGU, 89 (53, Fall Meet. S). Abstract A14C-07.

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Full text of Abstract : Fluxes of volatile organic compounds were measured above tropical rainforest and oil palm plantation in the Malaysian state of Sabah on the island of Borneo. During April and July 2008 an Ionikon proton transfer reaction mass spectrometer (ptrms) was operated at the 100 m Global Atmospheric Watch (GAW) tower at Bukit Atur, at the edge of the Danum Valley conservation area. An ultrasonic anemometer and air inlet were mounted at 76 m, with the ptrms housed in a laboratory building at the foot of the tower, measuring fluxes over tropical rainforest (selectively logged in 1989) with a typical canopy height of 30 to 40 m. In addition, during the July period, a second ptrms was coupled to a lift system which automatically moved an inlet to sample in-canopy gradients inside the forest canopy, between 2 and 30 m. During May 2008, the ptrms was moved to an oil palm plantation, north of the town of Lahad Datu, were fluxes were measured at a height of 15 m above the 12 m tall canopy, together with concentrations and fluxes of ozone and aerosols. These measurements formed part of two major UK projects: OP3-Danum-2008 (Oxidant and Particle Production Processes above South East Asian Rainforest) was aimed at quantifying biogenic emissions and evaluating their impact on air chemistry and the production of photo-oxidants and biogenic secondary organic aerosol, while ACES (Aerosol Coupling in the Earth System) studies the role of primary biogenic emissions, in-canopy processes and the effect of land-use change on aerosols. Initial results indicate that fluxes of isoprene above forest averaged 1.4 mg m-2 s-1 which is somewhat smaller than previous measurements in Amazonia and than previous estimates derived from leaf- level measurements, reflecting uncertainties in the assumed plant species composition. Concentrations peaked at the top of the canopy during midday. With an average of 5.5 mg m-2s-1, isoprene fluxes above the oil palm plantation were four times larger. Average fluxes of total monoterpenes were 0.15 mg m-2 s-1 at the forest site and 0.85 mg m-2 s-1 above oil palm. Fluxes of isoprene oxidation products (MVK + MACR) were upwards above forest and downward above oil palm, indicating that the high measurement height on the GAW tower provided more time for chemical conversion. Particle number fluxes above forest showed periods of apparent emission during midday indicative of VOC emissions resulting in particle growth.

Item Type: Publication - Article
Programmes: CEH Programmes pre-2009 publications > Biogeochemistry > BG01 Measuring and modelling trace gas, aerosol and carbon > BG01.5 Aerosols
UKCEH and CEH Sections/Science Areas: Billett (to November 2013)
ISSN: 0096-3941
NORA Subject Terms: Atmospheric Sciences
Date made live: 19 Feb 2009 10:08 +0 (UTC)

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