Environmental Engineering Reference
In-Depth Information
3.3 Results Provided by the Model and Validation
Data produced by our model confirmed the importance of monoterpene emis-
sion in Italy as their annual value (41.2 Gg y
−
1
) exceeded that of isoprene
(31.39 Gg y
−
1
). More than 85 % of monoterpenes were found to be released
from the T
+
L pool. About half of the emitted monoterpenes were composed
by
ʱ
-pinene (9.10 Gg y
−
1
), sabinene (4.34 Gg y
−
1
) and
ʲ
-pinene (3.37 Gg y
−
1
).
Limonene, myrcene,
trans
- and
cis
-beta ocimene, linalool, 1-8 cineol, camphene,
ʲ
-phellandrene and terpinolene contributed for the rest of the emission. Monthly
maps showed that more than 70 % of the emission occurred between June and
September, and it peaked in July. As shown in Fig.
3.3
, seasonal trend predicted
by our model for
ʱ
-pinene released in the coastal site of Castelporziano for the
year 2006 was consistent with flux measurements performed in 1997 (Ciccioli
et al.
2003
). Differences were mostly determined by the fact that the temperatures
in August 1997 were much higher than those of the same month of the year 2006.
As it can be seen, the contribution to monoterpene emission from deciduous and
evergreen species following a T
+
L mechanism, produced a strong seasonal vari-
ation of the emission, with very small values in the cold seasons. Our model also
indicates that the largest emission of isoprenoids occurs in Central-Southern Italy
and the two Italian islands (Sardinia and Sicily). Isoprenoid emission is concen-
trated most along the Appennines mountain range separating the east from the
west coasts of peninsular Italy. The intense light and temperature emission of
sabinene in these areas, which has never been reported before, reflects well the
dominance of
F. sylvatica
and
C. sativa
in forest ecosystems. The reduced emis-
sion of isoprene in these areas is instead determined by the fact that
Quercus
cerris
L., which is one of the dominant species, is a very low isoprenoid emitter
(0.1 µg leaf Dry Weight h
−
1
). If confirmed by field measurements, these
indications are of paramount importance in assessing the ozone production in the
Italian peninsula as sabinene reacts much faster with OH radicals than
ʱ
-pinene
and it has a comparable reactivity with ozone.
To confirm the importance of sabinene emission in the forest ecosystems
located in the Apennines, a field campaign was held in a CarboItaly site largely
dominated by
F. sylvatica.
The site (IT-Col) is located between 1,500 and 1,700 m
Fig. 3.3
Seasonal variations
of
ʱ
-pinene predicted by
the model for the year
2006 in the coastal site of
Castelporziano compared
with fluxes measured in 1997
