TY - JOUR

T1 - Fluxes and concentrations of volatile organic compounds from a South-East Asian tropical rainforest

AU - Langford, Ben

AU - Misztal, P. K.

AU - Nemitz, E.

AU - Davison, Brian

AU - Helfter, C.

AU - Pugh, Thomas

AU - Mackenzie, Rob

AU - Lim, S. F.

AU - Hewitt, C. N.

PY - 2010

Y1 - 2010

N2 - 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-May and June-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 degrees C and 1000 mu mol m(-2) s(-1) PAR, were 1.6 mg m(-2) h(-1) and 0.46mg m(-2) h(-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's tropical forests.

AB - 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-May and June-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 degrees C and 1000 mu mol m(-2) s(-1) PAR, were 1.6 mg m(-2) h(-1) and 0.46mg m(-2) h(-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's tropical forests.

KW - REACTION-MASS-SPECTROMETRY

KW - PTR-MS

KW - ISOPRENE EMISSION

KW - ATMOSPHERIC CHEMISTRY

KW - BOUNDARY-LAYER

KW - PERFORMANCE-CHARACTERISTICS

KW - MONOTERPENE FLUXES

KW - FIELD-MEASUREMENTS

KW - NORTH-ATLANTIC

KW - TECHNICAL NOTE

U2 - 10.5194/acp-10-8391-2010

DO - 10.5194/acp-10-8391-2010

M3 - Journal article

VL - 10

SP - 8391

EP - 8412

JO - Atmospheric Chemistry and Physics

JF - Atmospheric Chemistry and Physics

SN - 1680-7316

IS - 17

ER -