Direct ecosystem fluxes of volatile organic compounds from oil palms in South-East Asia
Article, Other literature type
Misztal, P. K.
Marco, C. F.
Phillips, G. J.
Hewitt, C. N.
MacKenzie, A. R.
Owen, S. M.
Heal, M. R.
Cape, J. N.
(issn: 1680-7324, eissn: 1680-7324)
PTR-MS | SOA | BVOC | Atmospheric Science | biosphere-atmosphere exchange | eddy covariance flux | /dk/atira/pure/subjectarea/asjc/1900/1902
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<sup>−2</sup> h<sup>−1</sup> 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<sup>−2</sup> h<sup>−1</sup>, with a small average canopy resistance
of 230 s m<sup>−1</sup>. 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<sup>−2</sup> h<sup>−1</sup>, 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<sup>−2</sup> h<sup>−1</sup> 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.