Environmental Engineering Reference
In-Depth Information
period. Recent improvements to processes governing the formation of secondary
organic aerosols were included in this model version (Henze et al., 2008). Global
emissions were developed using the Emission Database for Global Atmospheric
Research (Olivier et al., 1999) supplemented with more detailed inventories where
available, such as the European Monitoring and Evaluation Program (Auvray and
Bey, 2005).
The domain was divided into seven regions for analysis (
Fig. 1)
: Northeast
(NE), Southeast (SE), Industrial Midwest (IMW), Upper Midwest (UMW),
Southwest (SW), Northwest (NW), and Southern California (SCA). Influences on
background particulate matter concentrations on each region were evaluated
geographically (intercontinental transport or local) and by chemical precursor
(primary, secondary organic and inorganic species, etc.) by calculating sensitivity
coefficients using DDM-3D.
3. Results and Discussion
Both base PM
2.5
concentrations and the PRB show highly variable spatial and
approximately equal parts of sulfate, ammonium, nitrate, organic carbon, and
another nonreactive compounds
(Fig. 1).
In the summer, sulfate fraction becomes
more dominant, while nitrate decreases. Total concentrations are higher in the
winter months for all regions. Averaged PRB values are fairly constant throughout
organic PM from primary emissions from wild fires and secondary organic aerosol
formation results in the highest modeled annual PRB of 1.72 μg/m
3
. The influence
from the boundaries manifests primarily in elevated sulfate and organic carbon
concentrations with significant spatial and temporal variability (
Table 1)
.
Table 1.
Annually averaged PM
2.5
concentrations in μg/m
3
for the base run, PRB, and the
boundary influence
Base
PRB
Boundary
Northeast
9.76
0.74
0.52
Southeast
10.05
1.72
0.50
Industrial Midwest
11.38
0.86
0.51
Upper Midwest
6.70
0.84
0.54
Southwest
3.30
0.62
0.38
Northwest
2.72
1.01
0.46
Southern California
4.43
0.84
0.53
