Environmental Engineering Reference
In-Depth Information
apportionment technique. The predicted SOA concentration in the current model
simulation matches the calculated “unknown” OA using molecular markers at all
sites and times except during nighttime hours at Bakersfield, which may indicate
an under-prediction of SOA concentrations at this time and location. Under
prediction of SOA formation is not surprising given that our current understanding
of SOA formation is far from complete [4].
The predicted SOA accounts for approximately 20% of the predicted OA
averaged across the entire SJV, indicating the importance of considering the best
available estimates of wintertime SOA in regional model calculations. Urban
locations are dominated by POA and so predicted SOA only accounts for
approximately 5% of total OA at urban locations such as Fresno and Bakersfield.
However, predicted SOA can constitute up to 50% of predicted OA at certain rural
locations within the SJV and along the coastlines north of San Francisco (SF).
Table 1.
Source apportionment of SOA at selected locations in Central California between
December 25, 2000 and January 7, 2001
a
FRES
b
ANG
b
BAC
b
SJV
b
Sources
Initial/boundary conditions
0.014
0.009
0.008
0.009
Solvent use
0.776
0.664
0.469
0.376
Wood smoke
0.401
0.322
0.244
0.212
Diesel engines
0.030
0.043
0.027
0.022
Non-catalyst gasoline engines
0.312
0.303
0.204
0.173
Catalyst gasoline engines
0.611
0.610
0.432
0.332
Gasoline storage and disposal
0.045
0.042
0.032
0.023
High sulfur fuel combustion
0.010
0.032
0.011
0.027
Other anthropogenic sources
0.212
0.242
0.236
0.147
Biogenic source
0.026
0.016
0.018
0.030
Total SOA
2.463
2.284
1.680
1.351
a
Unit in µg m
−3
b
FRES: Fresno; ANG: Angiola; BAC: Bakersfield; SJV: average of the entire SJV
Table 1
gives the total SOA concentrations and SOA source contributions
predicted by the UCD/CIT/CACM model for Fresno, Angiola, Bakersfield, and
the entire SJV averaged between December 25, 2000, and January 7, 2001.
Angiola is a rural location within the SJV in contrast to urban locations such as
Fresno and Bakersfield. However, major sources for SOA formation are fairly
consistent among these locations. Solvent use, catalyst gasoline engines, wood
smoke, non-catalyst gasoline engines, and other anthropogenic sources are major
SOA contributors, accounting for ~28-32%, ~25-27%, ~14-16%, ~12-13%, and
~9-14% of SOA formation, respectively. Contributions from the remaining
sources are minor, accounting for only ~5-8% of the SOA.
