Atmospheric Chemistry and Physics
www.atmos-chem-phys.net
1680-7316
1680-7324
8
24
2008
10.5194/acp-8-7367-2008
http://www.atmos-chem-phys.net/8/7367/2008/
http://www.atmos-chem-phys.net/8/7367/2008/acp-8-7367-2008.html
http://www.atmos-chem-phys.net/8/7367/2008/acp-8-7367-2008.pdf
7367
7371
2008-12-11
Emission of sunscreen salicylic esters from desert vegetation and their contribution to aerosol formation
S. N. Matsunaga
A. B. Guenther
M. J. Potosnak
E. C. Apel
Advanced Study Program, National Center for Atmospheric Research, 3450 Mitchell Lane, Boulder CO 80301, USA
Atmospheric Chemistry Division, National Center for Atmospheric Research, 3450 Mitchell Lane, Boulder CO 80301, USA
Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512, USA
Biogenic volatile organic compounds (BVOC) produced by plants are known to
have an important role in atmospheric chemistry. However, our knowledge of
the range of BVOCs produced by different plant processes is still expanding,
and there remain poorly understood categories of BVOCs. In this study,
emissions of a novel class of BVOC emissions were investigated in a desert
region. Our study considered 8 species of common desert plants: blackbrush
(<i>Coleogyne ramosissima</i>), desert willow (<i>Chilopsis linearis</i>),
mesquite (<i>Prosopis glandulosa</i>), mondel pine (<i>Pinus eldarica</i>),
pinyon pine (<i>Pinus monophylla</i>), cottonwood (<i>Populus deltoides</i>),
saguaro cactus (<i>Carnegiea gigantea</i>) and yucca (<i>Yucca baccata</i>).
The measurements focused on BVOCs with relatively high molecular weight (>C<sub>15</sub>) and/or an
oxygenated functional group. Significantly high emission rates of two
salicylic esters were found for blackbrush, desert willow and mesquite with
emission rates of 3.1, 1.0 and 4.8μgC dwg<sup>−1</sup> h<sup>−1</sup>,
respectively (dwg; dry weight of the leaves in gram). The salicylic esters
were identified as 2-ethylhexenyl salicylate (2-EHS) and
3,3,5-trimethylcyclohexenyl salicylate (homosalate) and are known as
effective ultraviolet (UV) absorbers. We propose that the plants derive a
protective benefit against UV radiation from the salicylic esters and that
the emission process is driven by the physical evaporation of the salicylic
esters due to the high ambient temperatures. In addition, the salicylic
esters are predicted to be an effective precursor of secondary organic
aerosol (SOA) because they probably produce oxidation products that can
condense onto the aerosol phase. We estimated the contribution of the
sunscreen esters themselves and their oxidation products on the SOA
formation for the Las Vegas area using a BVOC emission model. The
contribution was estimated to reach 50% of the biogenic terpenoid
emission in the landscapes dominated by desert willow and mesquite and
13% in the Las Vegas area. The contributions to biogenic SOA are likely
to be higher due to the potentially high SOA yields of these compounds.
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