Articles | Volume 16, issue 11
Research article
08 Jun 2016
Research article |  | 08 Jun 2016

Current estimates of biogenic emissions from eucalypts uncertain for southeast Australia

Kathryn M. Emmerson, Ian E. Galbally, Alex B. Guenther, Clare Paton-Walsh, Elise-Andree Guerette, Martin E. Cope, Melita D. Keywood, Sarah J. Lawson, Suzie B. Molloy, Erin Dunne, Marcus Thatcher, Thomas Karl, and Simin D. Maleknia

Abstract. The biogenic emissions of isoprene and monoterpenes are one of the main drivers of atmospheric photochemistry, including oxidant and secondary organic aerosol production. In this paper, the emission rates of isoprene and monoterpenes from Australian vegetation are investigated for the first time using the Model of Emissions of Gases and Aerosols from Nature version 2.1 (MEGANv2.1); the CSIRO chemical transport model; and atmospheric observations of isoprene, monoterpenes and isoprene oxidation products (methacrolein and methyl vinyl ketone). Observations from four field campaigns during three different seasons are used, covering urban, coastal suburban and inland forest areas. The observed concentrations of isoprene and monoterpenes were of a broadly similar magnitude, which may indicate that southeast Australia holds an unusual position where neither chemical species dominates. The model results overestimate the observed atmospheric concentrations of isoprene (up to a factor of 6) and underestimate the monoterpene concentrations (up to a factor of 4). This may occur because the emission rates currently used in MEGANv2.1 for Australia are drawn mainly from young eucalypt trees (< 7 years), which may emit more isoprene than adult trees. There is no single increase/decrease factor for the emissions which suits all seasons and conditions studied. There is a need for further field measurements of in situ isoprene and monoterpene emission fluxes in Australia.

Short summary
We have tested how a model using a global inventory of plant-based emissions compares with four sets of measurements made in southeast Australia. This region is known for its eucalypt species, which dominate the summertime global inventory. The Australian part of the inventory has been produced using measurements made on eucalypt saplings. The model could not match the measurements, and the inventory needs to be improved by taking measurements of a wider range of Australian plant types and ages.
Final-revised paper