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| Titel |
A comprehensive emission inventory of biogenic volatile organic compounds in Europe: improved seasonality and land-cover |
| VerfasserIn |
D. C. Oderbolz, S. Aksoyoglu, J. Keller, I. Barmpadimos, R. Steinbrecher, C. A. Skjøth, C. Plass-Dülmer, A. S. H. Prévôt |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 13, no. 4 ; Nr. 13, no. 4 (2013-02-15), S.1689-1712 |
| Datensatznummer |
250017655
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| Publikation (Nr.) |
 copernicus.org/acp-13-1689-2013.pdf |
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| Zusammenfassung |
| Biogenic volatile organic compounds (BVOC) emitted from vegetation are
important for the formation of secondary pollutants such as ozone and
secondary organic aerosols (SOA) in the atmosphere. Therefore, BVOC emission
are an important input for air quality models. To model these emissions with
high spatial resolution, the accuracy of the underlying vegetation inventory
is crucial. We present a BVOC emission model that accommodates different
vegetation inventories and uses satellite-based measurements of greenness
instead of pre-defined vegetation periods. This approach to seasonality
implicitly treats effects caused by water or nutrient availability, altitude
and latitude on a plant stand. Additionally, we test the influence of
proposed seasonal variability in enzyme activity on BVOC emissions. In its
present setup, the emission model calculates hourly emissions of isoprene,
monoterpenes, sesquiterpenes and the oxygenated volatile organic compounds
(OVOC) methanol, formaldehyde, formic acid, ethanol, acetaldehyde, acetone
and acetic acid. In this study, emissions based on three different vegetation
inventories are compared with each other and diurnal and seasonal variations
in Europe are investigated for the year 2006. Two of these vegetation
inventories require information on tree-cover as an input. We compare three
different land-cover inventories (USGS GLCC, GLC2000 and Globcover 2.2) with
respect to tree-cover. The often-used USGS GLCC land-cover inventory leads to
a severe reduction of BVOC emissions due to a potential miss-attribution of
broad-leaved trees and reduced tree-cover compared to the two other
land-cover inventories. To account for uncertainties in the land-cover
classification, we introduce land-cover correction factors for each relevant
land-use category to adjust the tree-cover. The results are very sensitive to
these factors within the plausible range. For June 2006, total monthly BVOC
emissions decreased up to −27% with minimal and increased up to +71%
with maximal factors, while in January 2006, the changes in monthly BVOC
emissions were −54 and +56% with minimal and maximal factors,
respectively. The new seasonality approach leads to a reduction in the annual
emissions compared with non-adjusted data. The strongest reduction occurs in
OVOC (up to −32%), the weakest in isoprene (as little as −19%). If
also enzyme seasonality is taken into account, however, isoprene reacts with
the steepest decrease of annual emissions, which are reduced by −44% to
−49%, annual emissions of monoterpenes reduce between −30 and
−35%. The sensitivity of the model to changes in temperature depends on
the climatic zone but not on the vegetation inventory. The sensitivity is
higher for temperature increases of 3 K (+31% to +64%) than decreases
by the same amount (−20 to −35%). The climatic zones "Cold except
summer" and "arid" are most sensitive to temperature changes in January
for isoprene and monoterpenes, respectively, while in June, "polar" is most
sensitive to temperature for both isoprene and monoterpenes. Our model
predicts the oxygenated volatile organic compounds to be the most abundant
fraction of the annual European emissions (3571–5328 Gg yr−1),
followed by monoterpenes (2964–4124 Gg yr−1), isoprene
(1450–2650 Gg yr−1) and sesquiterpenes (150–257 Gg yr−1). We
find regions with high isoprene emissions (most notably the Iberian
Peninsula), but overall, oxygenated VOC dominate with 43–45% (depending
on the vegetation inventory) contribution to the total annual BVOC emissions
in Europe. Isoprene contributes between 18–21%, monoterpenes 33–36%
and sesquiterpenes contribute 1–2%. We compare the concentrations of
biogenic species simulated by an air quality model with measurements of
isoprene and monoterpenes in Hohenpeissenberg (Germany) for both summer and
winter. The agreement between observed and modelled concentrations is better
in summer than in winter. This can partly be explained with the difficulty to
model weather conditions in winter accurately, but also with the increased
anthropogenic influence on the concentrations of BVOC compounds in winter.
Our results suggest that land-cover inventories used to derive tree-cover
must be chosen with care. Also, uncertainties in the classification of
land-cover pixels must be taken into account and remain high. This problem
must be addressed together with the remote sensing community. Our new
approach using a greenness index for addressing seasonality of vegetation can
be implemented easily in existing models. The importance of OVOC for air
quality should be more deeply \mbox{addressed} by future studies, especially
in smog chambers. Also, the fate of BVOC from the dominant region of the
Iberian Peninsula should be studied more in detail. |
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