The Sensitivity of Aerosol Sulfate to Changes in Nitrogen Oxides and Volatile Organic Compounds...
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Transcript of The Sensitivity of Aerosol Sulfate to Changes in Nitrogen Oxides and Volatile Organic Compounds...
The Sensitivity of Aerosol Sulfate to Changes in Nitrogen Oxides and
Volatile Organic Compounds
Ariel F. Stein Department of Meteorology
The Pennsylvania State University
Sulfate
• Is the dominant inorganic constituent of PM2.5
• Reduces visibility because of its hygroscopic characteristics. Hazy summer days.
• Dry and wet deposition of sulfate: elevates the acidity levels in surface waters and soil.
• Affects regional and global climates by scattering radiation.
HOx cycle
Sinks: R O O HH O2 2
RO 2
HO 2
CO, VOC, O 3
NO, O 3
R H C O
H N O 3
NO 2
O H
h
O 3
H O2
Sources:
h
• SHOx = PHNO3 + 2 PXOOH + PPAN
• PSO4 = P H2O2 + P SO4G
• PSO4 = f([NOx] , [VOC])
• [VOC] d PSO4/d[VOC] = [NOx] d PSO4/d[NOx]
Sensitivity of SO42- to changes in
NOx and VOC abundance
))((
)(
G4SOG4SO
G4SO
Threshold3HNO
4SO
x2x1
x2k
PP
PH2O2=kH2O2[HO2]2
PSO4G=kSO4G[SO2][OH]
Streamline analysis 14 Jul 1995 1200 UTC
Ozone Concentrations
MODELS-3 description
• Community Multiscale Air Quality (CMAQ) model. 3-D Eulerian chemical transport model.
• Meteorology: Mesoscale Model 5 (MM5)
• Emissions: MODELS-3 Emissions Processing and Projection System (MEPPS).
• Chemical mechanism: RADM2
• Aerosol model: Regional Particulate Model (RPM)
• Horizontal resolution: 36 km
• Vertical layers: 15
• Domain: Northeastern USA.
N 327
1-h Peak Raw bias (ppb)a -9.7
Norm bias (%)b -7.3
Raw gross error (ppb)c 18.3
Norm gross error (%)d 18.5
Early morning (6-9 AM) Raw bias (ppb)a -1.4
Raw gross error (ppb)c 16.2
Late night (2-5 AM) Raw bias (ppb)a 6.4
Raw gross error (ppb)c 18.6
Normalized bias (%)b O3>20 ppb 5.1
O3>40 ppb -6.3
O3>60 ppb -11.8
Raw bias (ppb)a O3>20 ppb -2.6
O3>40 ppb -7.0
O3>60 ppb -11.3
Normalized gross error (%)d O3>20 ppb 33.4
O3>40 ppb 25.7
O3>60 ppb 22.5
Raw gross error (ppb)c O3>20 ppb 18.3
O3>40 ppb 18.5
O3>60 ppb 19.5
a R a w b i a s : 1
1N i
N
[ ]C ( t ) C ( t )p , i o , i
b N o r m a l i z e d r a w b i a s :
1
1N i
N [ ]C ( t ) C ( t )
C ( t )
p , i o , i
o , i
c R a w g r o s s e r r o r :
1
1N i
N
C ( t ) C ( t )p , i o , i
d N o r m a l i z e d g r o s s e r r o r :
1
1N i
N C ( t ) C ( t )
C ( t )
p , i o , i
o , i
w h e r e C p i s t h e m o d e l e d c o n c e n t r a t i o n a n dC o i s t h e m e a s u r e d c o n c e n t r a t i o n .
NOx and VOC sensitivity definition
NONOxx-sensitive locations -sensitive locations
{ [O3]35%NOx - [O3]35%VOC }< 5 ppb (~5%)
{{[H2O2]+[SO42-]}35%NOx - {[H2O2]+[SO4
2-]}35%VOC}<0.5 ppb (~5%)
________________________________________________________
VOC-sensitive locationsVOC-sensitive locations
{ [O3]35%NOx - [O3]35%VOC }> 5 ppb (~5%)
{{[H2O2]+[SO42-]}35%NOx - {[H2O2]+[SO4
2-]}35%VOC}>0.5 ppb (~5%)
Indicator / run
VOC sensitive
50th percentile
locations
95th percentile
NOx sensitive
5th percentile
locations
50th percentile
H2O2/HNO3
BASECASE 0.16 0.21 0.49 1.30
DBLSO2 0.17 0.22 0.57 1.83
DBLVOC 0.14 0.30 0.70 2.22
Sillman et al.[1997] (0.13-0.33) (0.24-0.59) (0.28-0.68) (0.73-1.58)
O3/NOz
BASECASE 8.3 9.6 12.3 25.7
DBLSO2 8.4 9.7 12.4 25.7
DBLVOC 6.8 9.6 12.7 25.8
Sillman et al.[1997] (5.8-8.6) (7.7-10.4) (7.9-11.9) (11.8-17.7)
Distribution of ozone sensitivity indicator values
Potential sulfate reduction as a function of the non-dimensional indicator.
-15
-10
-5
0
5
10
15
0.1 1 10
{[H2O2]+[SO42-]}/{[HNO3]+[NO3
-]}
{[H
2O2]
+[S
O42-
]} r
edu
ctio
n[%
]
35% NOx reductions 35% VOC reductions
Distribution of {[H2O2]+[SO42-]}/{[HNO3]+[NO3
-]} ratios for NOx- and VOC- sensitive regimes
Run 5th
percentile
VOC sensitive
50th
percentile
locations
95th
percentile
NOx sensitive
5th
percentile
locations
50th
percentile
95th
percentile
BASECASE 0.47 0.96 1.82 1.54 7.30 18.66
DBLSO2 0.30 0.89 1.37 1.73 4.76 16.86
DBLVOC 0.65 1.23 2.25 1.60 7.46 20.16
Geographical distribution of the VOC-sensitive locations for July 14 at 20:00 UTC. Shaded regions correspond to
indicator values lower than 1.
Conclusions The species ratios consistently assume
different values under NOx_sensitive and VOC_sensitive conditions.
Indicator values > 2 ==> NOx sensitivity.
Indicator values < 1.5 ==> VOC sensitivity. The value of the indicator at the transition
point between NOx_ and VOC_sensitive sulfate remains constant throughout the different runs.