Armin Hansel, Armin Wisthaler, Martin
Graus
Institut für Ionenphysik, Universität Innsbruck, Austria
15.07.2005, 13.00 c.t.
Room S3120
The main interest in tropospheric volatile organic compounds (VOC) originating from biogenic and anthropogenic sources is that these trace gases can have a significant impact on levels of oxidants such as ozone (O3) and the hydroxyl radical (OH), and on secondary organic aerosol formation. Photochemical reactions of VOC in the troposphere are complex, depending on the presence of OH, NOx and UV-light. A VOC generally contributes more to ozone formation the higher its density is and the faster its reaction with OH radicals proceeds. Thus, in order to understand quantitatively tropospheric ozone chemistry, it is necessary to know the VOC distribution within the troposphere as well as VOC fluxes from individual sources.
The global anthropogenic VOC flux is estimated as 1 x 1014 g C a-1,
while biogenic sources may be higher by a factor of ten (1.2 x 1015 g
C a-1). Reactive biogenic volatile organic compounds (BVOC) include
the quantitatively dominant group of isoprenoids (isoprene and monoterpenes (e.g.,
α-pinene)) and oxygen-containing species, such as alcohols and carbonyls. Within
the plant kingdom only certain plant species emit isoprenoids. Generally,
isoprene emission is more frequently reported for deciduous plants whereas
monoterpene emission is common for evergreen leaves. Both isoprene and
monoterpene emission rates are strongly regulated by light and temperature.
Emission of all biogenic VOC is also constrained by water and nitrogen
availability in the soil and the development stage of the leaves. The complex
regulation processes of the emission of an ecosystem as a result of the
interaction of molecular biology, biochemistry, ecology, air chemistry and
physics still remains to be elucidated.
In this paper we will highlight how the use of Proton Transfer Reaction
Mass-Spectrometer (PTR-MS) technology has enhanced our understanding of
anthropogenic VOC emissions, biosphere-atmosphere exchange processes, and
photochemical processing of both anthropogenic and biogenic VOC in the
troposphere.