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@ARTICLE{Derstroff:836874,
author = {Derstroff, Bettina and Hüser, Imke and Bourtsoukidis,
Efstratios and Crowley, John N. and Fischer, Horst and
Gromov, Sergey and Harder, Hartwig and Janssen, Ruud H. H.
and Kesselmeier, Jürgen and Lelieveld, Jos and Mallik,
Chinmay and Martinez, Monica and Novelli, Anna and
Parchatka, Uwe and Phillips, Gavin J. and Sander, Rolf and
Sauvage, Carina and Schuladen, Jan and Stönner, Christof
and Tomsche, Laura and Williams, Jonathan},
title = {{V}olatile organic compounds ({VOC}s) in photochemically
aged air from the eastern and western {M}editerranean},
journal = {Atmospheric chemistry and physics},
volume = {17},
number = {15},
issn = {1680-7324},
address = {Katlenburg-Lindau},
publisher = {EGU},
reportid = {FZJ-2017-05910},
pages = {9547 - 9566},
year = {2017},
abstract = {During the summertime CYPHEX campaign (CYprus PHotochemical
EXperiment 2014) in the eastern Mediterranean, multiple
volatile organic compounds (VOCs) were measured from a
650 m hilltop site in western Cyprus
(34° 57′ N/32° 23′ E). Periodic shifts in the
northerly Etesian winds resulted in the site being
alternately impacted by photochemically processed emissions
from western (Spain, France, Italy) and eastern (Turkey,
Greece) Europe. Furthermore, the site was situated within
the residual layer/free troposphere during some nights which
were characterized by high ozone and low relative humidity
levels. In this study we examine the temporal variation of
VOCs at the site. The sparse Mediterranean scrub vegetation
generated diel cycles in the reactive biogenic hydrocarbon
isoprene, from very low values at night to a diurnal median
level of 80–100 pptv. In contrast, the oxygenated
volatile organic compounds (OVOCs) methanol and acetone
exhibited weak diel cycles and were approximately an order
of magnitude higher in mixing ratio (ca. 2.5–3 ppbv
median level by day, range: ca. 1–8 ppbv) than the
locally emitted isoprene and aromatic compounds such as
benzene and toluene. Acetic acid was present at mixing
ratios between 0.05 and 4 ppbv with a median level of ca.
1.2 ppbv during the daytime. When data points directly
affected by the residual layer/free troposphere were
excluded, the acid followed a pronounced diel cycle, which
was influenced by various local effects including
photochemical production and loss, direct emission, dry
deposition and scavenging from advecting air in fog banks.
The Lagrangian model FLEXPART was used to determine
transport patterns and photochemical processing times
(between 12 h and several days) of air masses originating
from eastern and western Europe. Ozone and many OVOC levels
were ∼ 20 and $ ∼ 30–60 \%$ higher,
respectively, in air arriving from the east. Using the
FLEXPART calculated transport time, the contribution of
photochemical processing, sea surface contact and dilution
was estimated. Methanol and acetone decreased with residence
time in the marine boundary layer (MBL) with loss rate
constants of 0.74 and 0.53 day−1 from eastern Europe and
0.70 and 0.34 day−1 from western Europe, respectively.
Simulations using the EMAC model underestimate these loss
rates. The missing sink in the calculation is most probably
an oceanic uptake enhanced by microbial consumption of
methanol and acetone, although the temporal and spatial
variability in the source strength on the continents might
play a role as well. Correlations between acetone and
methanol were weaker in western air masses
(r2 = 0.68), but were stronger in air masses
measured after the shorter transport time from the east
(r2 = 0.73).},
cin = {IEK-8},
ddc = {550},
cid = {I:(DE-Juel1)IEK-8-20101013},
pnm = {243 - Tropospheric trace substances and their
transformation processes (POF3-243)},
pid = {G:(DE-HGF)POF3-243},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000407386800001},
doi = {10.5194/acp-17-9547-2017},
url = {https://juser.fz-juelich.de/record/836874},
}