Flux estimates of isoprene, methanol and acetone from airborne PTR-MS measurements over the tropical rainforest during the GABRIEL 2005 campaign

摘要

Tropical forests are a strong source of biogenic volatile organic compounds (BVOCs) to the atmosphere which can potentially impact the atmospheric oxidation capacity. Here we present airborne and ground-based BVOC measurements representative for the long dry season covering a large area of the northern Amazonian rainforest (6-3 deg; N, 50-59 deg; W). The measurements were conducted during the October 2005 GABRIEL (Guyanas Atmosphere-Biosphere exchange and Radicals Intensive Experiment with the Learjet) campaign. The vertical (35 m to 10 km) and diurnal (09:00-16:00) profiles of isoprene, its oxidation products methacrolein and methyl vinyl ketone and methanol and acetone, measured by PTR-MS (Proton Transfer Reaction Mass Spectrometry), have been used to empirically estimate their emission fluxes from the forest canopy on a regional scale. The mixed layer isoprene emission flux, inferred from the airborne measurements above 300 m, is 5.7 mg isoprene m~2 h~1 after compensating for chemistry and ～6.9 mg isoprene m~2 h~1 taking detrainment into account. This surface flux is in general agreement with previous tropical forest studies. Inferred methanol and acetone emission fluxes are 0.5 mg methanol m~2 h~1 and 0.35 mg acetone m ~2 h