Atmospheric Formation of Ultrafine Particles...220 fixed size sections ranging in size from 0.8 nm...
Transcript of Atmospheric Formation of Ultrafine Particles...220 fixed size sections ranging in size from 0.8 nm...
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Atmospheric Formation of Ultrafine Particles
Charles Stanier, Assistant ProfessorUniversity of IowaDepartment of Chemical and
Biochemical [email protected]
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Outline
What is atmospheric new particle formationSome examples
Physical measurementsChemical measurementsModeling
What fraction of particles are from new particle formation vs. combustion?
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What is Nucleation?
Molecules
Neutral or ion clusters
Ternary or Ion-Induced Nucleation
Detectable Aerosol Particles0.01-10 cm-3s-1 regional eventsup to 105 cm-3s-1 in plumes
Initial Growth
Further Growth (1-20 nm/hr)
CCNAmmoniumSulfateOrganics~ 1 nm 3 nm
LossBy
CondensationTo Pre-existingSurface Area
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Nucleation Overview
SO2(g) + OH· + H2O →HO2· + H2SO4·nH2O
SO2
NH3
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Nucleation Observations
Kulmala, McMurry, et al. (2004) J. Aerosol Sci. 35 pp. 143-176
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Particle Size
nmµm
10.001
100.01
1000.1
1,0001 10 100
Ultrafine
Fine Particles (< 2.5 µm)
Con
cent
ratio
n Number Distribution
Mass Distribution
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Diurnal Pattern
0
20,000
40,000
60,000
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Hour
3-50
0 nm
Par
ticle
Cou
nt (c
m-3
)
Non-nucleation w orkdays Non-nucleation w eekends
Regional nucleation days
(b)
0
20,000
40,000
60,000
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Hour
3-50
0 nm
Par
ticle
Cou
nt (c
m-3
)
Non-nucleation w orkdays Non-nucleation w eekends
Regional nucleation days
(b)
Non-nucleation w orkdays Non-nucleation w eekends
Regional nucleation days
(b)
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0 25 50 75 100
Number vs. Mass Distribution
Pittsburgh, PA2001-2002
Aerosol Mass (µg/m3)
Num
ber
(#/c
m3 )
10x104
20x104
Negative correlationRelated to nucleation activityOccurring over wide area
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New Particle Formation vs. Visibility
USX Tower
USX Tower
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Other Aerosol Impacts: Visibility & Climate
EPA (2001) National Air Quality: Status and Trends
Yosemite, CA
CloudFormation
CloudParticles
ScatteredRadiation
ScatteredRadiation
Earth
Sun
CloudFormation
CloudParticles
ScatteredRadiation
ScatteredRadiation
Earth
Sun
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Physical Measurements
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Dry-Ambient Aerosol Size Spectrometer
Reconfigured commercial instrumentsRH control systemInlet particle losses characterizationCustom control, data acquisition, and data reduction software
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Nucleation Frequency by Month
0%
50%
100%
Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
> 1-hr Duration < 1-hr Duration None
2001 2002
Frac
tion
of
Day
s W
ith
Nu
clea
tion
Significant fraction of days (30%+)Most prevalent in spring, fall
Pittsburgh 2001-2002
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Example: No NucleationP
arti
cle
Size
(n
m)
10
100
500
00:00Time of Day
06:00 12:00 18:00 24:00
105
104
103
102
Res
pon
sedN
/dlo
gDp
(cm
-3)
Nu
mbe
r (#
/cm
3)
12x104
6x104
Pittsburgh, August 10, 2001
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Example: Weak Nucleation
105
104
103
102
Res
pon
sedN
/dlo
gDp
(cm
-3)
Par
ticl
e Si
ze (
nm
)
10
100
500
Nu
mbe
r (#
/cm
3)
12x104
6x104
00:00Time of Day
06:00 12:00 18:00 24:00
Pittsburgh, July 2, 2001
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Sunlight and New Particle Formation
SUNRISE
Cloudy Morning
00:00Time of Day
06:00 12:00 18:00 24:00
Cloud Free Morning
Par
ticl
e Si
ze (
nm
)
10
100
500
10
100
500Pittsburgh
Nov 10, 2001
PittsburghNov 11, 2001
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Nucleation’s Spatial Coverage
Method: simultaneous sampling
WindPittsburgh Philadelphia
RuralSampler
Main (Urban)Sampler
PhiladelphiaSampler
38 km 400 km
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Spatial Coverage ResultP
arti
cle
Size
(n
m)
10
100
200
10
100200
38 km apartFebruary 25, 2002
Pittsburgh
38 km Upwind Rural Location
400 km apartJuly 2, 2001
Pittsburgh
Philadelphia
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Diurnal Pattern
0
20,000
40,000
60,000
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Hour
3-50
0 nm
Par
ticle
Cou
nt (c
m-3
)
Non-nucleation w orkdays Non-nucleation w eekends
Regional nucleation days
(b)
0
20,000
40,000
60,000
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Hour
3-50
0 nm
Par
ticle
Cou
nt (c
m-3
)
Non-nucleation w orkdays Non-nucleation w eekends
Regional nucleation days
(b)
Non-nucleation w orkdays Non-nucleation w eekends
Regional nucleation days
(b)
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Chemical Measurements
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Aerosol Mass Spectrometer
Zhang, Q.; Jimenez, J.L.; Caragaratna, M.; Worsnop, D.
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Aerosol Mass Spectrometer
Particle Inlet (1 atm)
Jayne et al., Aerosol Science and Technology 33:1-2(49-70), 2000.Jimenez et al., Journal of Geophysical Research, in press, 2002.
QuadrupoleMass Spectrometer
Thermal Vaporization
&Electron Impact
Ionization
Aerodynamic Lens
(2 Torr)
Chopper
Turbo Pump
Turbo Pump
Turbo Pump
Time of Flight Region
Particle BeamGeneration
Aerodynamic Sizing Particle Composition
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September 12, 2002 Nucleation EventP
arti
cle
Size
(n
m)
10
100
500
00:00 06:00 12:00 18:00 24:00
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September 12, 2002 Nucleation EventP
arti
cle
Size
(n
m)
10
100
500
00:00 06:00 12:00 18:00 24:00
50%
0%
100%
Mas
s Fr
acti
on1
0-6
0 n
m
Nitrate
Ammonium
SulfateOrganics
Mass Fraction (10-60 nm Particles) Aerosol Mass Spectrometer*
*Zhang & Jimenez (Univ. Colorado-Boulder)
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Chemistry of Growth: Particle Mass Spectra at 20-33 nm
Detection of Nucleationby Particle Sizer
Zhang, et. al. Insights into the Chemistry of Nucleation Bursts and New Particle Growth Events in Pittsburgh based on Aerosol Mass Spectrometry. Environ. Sci. Technol., in press.
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Modeling
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Chemistry of Nucleation: Simulation1
SO2(g) + OH· + H2O →HO2· + H2SO4·nH2O
SO2
Inputs Processes Modeled OutputPreexisting Aerosol Distribution
SO2 ConcentrationNH3 ConcentrationUV Light IntensityTemperature & RH
NH3
SO2 Oxidation to H2SO4H2SO4-H2O-NH3 Nucleation
H2SO4 CondensationParticle Coagulation
Predicted Aerosol Distribution
1Model adapted from Capaldo, Kasibhatla, Pandis. J. Geophys. Res., 1999.
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Modeling H2SO4 Nucleation
Photochemical box model
Modeled gas-phase species:SO2, H2SO4, OH, NH3SO2 measured, OH and NH3 calculated from measurements
220 fixed size sections ranging in size from 0.8 nm to 10 µm
T, RH, SO2 and UV radiation from measurements
Initial distribution available from dry size distributions
Maximum OH concentration assumed for each month, scaled based onUV
5 x 106 molecules/cm3 in summer11 x 106 molecules/cm3 in winter2
1Ren et al. (2003)2Heard et al. (2001)
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Comparison on July 27, 2001
Model predicted presence or lack of nucleation on all 19 daysTiming of onset of nucleation within one hour of observations for all 13 eventsSize and shape of growth curve consistent with observationsHigh number concentrations predicted
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Comparison on January 28, 2002
25 out of 29 days predicted correctlyTiming of onset of nucleation not as good (6 of 12 within one hour)Growth generally underpredictedwith two exceptionsHigh number concentrations predicted
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Sensitivities
NPF is thought to be sensitive to:PM2.5 ↓ NPF ↑Ammonia ↑ NPF ↑ (but not sure how strong this effect)SO2 ↓ NPF ↓ (if NH3 in excess … that covers
most locations)SO2 ↓ NPF ↑ (if NH3 limited, e.g. northeast U.S.
in summer)Reactive VOCs ↓NPF ? – but growth of particles will be
limited – so they will not last aslong in the atmosphere
0102030405060708090100
-100-80 -60 -40 -20 0 20 40 60 80 1000
2
4
6
8
10
12
14
16
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Day
s w
ith n
ucle
atio
n
Change in SO2 Concentration (%)
July
% o
f mod
eled
day
s
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What fraction of ultrafines are from NPF?
To a large extent, we do not knowWill vary by locationNPF most important at midday and afternoons
Traffic
Smog
and
Reg
iona
l Haz
e NPF LessImportant
NPF MoreImportant
Threshold chemistrystill Unclear (SO2 + ???)and will vary from place to pla
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Traffic
Smog
and
Reg
iona
l Haz
e NPF LessImportant
NPF MoreImportant
Heavy TrafficUrban
AfternoonDownwindSuburbs
Rura
l U.S
.
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0
10000
20000
30000
40000
50000
0:00 6:00 12:00 18:00 0:00
#/cc
C C a t c e Cou t (b ue) s S S a t c e Cou t ( ed)Pa
rtic
le S
ize
(nm
)
Res
pons
edN
/dlo
gDp
(cm
-3)
Bondville Illinois, 2005
Traffic
Smog
and
Reg
iona
l Haz
e NPF LessImportant
NPF MoreImportant
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Mexico City Mar 17, 2006
Traffic
Smog
and
Reg
iona
l Haz
e NPF LessImportant
NPF MoreImportant
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Pittsburgh PA
NOV 1
NOV 2
NOV 3
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Pittsburgh PA
NOV 1
NOV 2
NOV 3
Traffic
Smog
and
Reg
iona
l Haz
e NPF LessImportant
NPF MoreImportant
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DOWNY DEC 2000 RIVERSIDE MAY 2001
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DOWNY DEC 2000 RIVERSIDE MAY 2001
Traffic
Smog
and
Reg
iona
l Haz
e NPF LessImportant
NPF MoreImportant
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Future Work
In the process of summarizing comparisons between Pittsburgh, Rochester, New York City, Atlanta, LA, and St. Louis.Unify measurements, detailed modeling, and a “screening” model that attributes ultrafines to traffic vs. new particle formationSort out some details of chemistry and meteorologyMonitor how implementation of further sulfur reductions from power plants, and advanced diesel influence new particle formation
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Acknowledgements
Students:Alicia Kalafut – Ultrafine Particle SamplingKazeem Olanrewaju – Ultrafine Particle Modeling
University of Iowa Callaborators:Greg Carmichael, Jerry Schnoor, Bill Eichinger
Carnegie Mellon Collaborators:Spyros Pandis, Tim Gaydos, Andrey Khlystov,
Outside Collaborators:Allen Williams
Illinois Soil and Water SurveyPeter McMurry
University of MinnesotaJimenez Group, University of Colorado-Boulder
Jose-Luis Jimenez & Qi Zhang
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Additional Material
Modeling FrameworkFuture WorkMeasurement TechniqueTraffic and ModelingBondvilleMexicoBackground on PM
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Modeling framework
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Modeling H2SO4 Nucleation
Photochemical box modelModeled gas-phase species:
SO2, H2SO4, OH, NH3SO2 measured, OH and NH3 calculated from measurements
220 fixed size sectoins ranging in size from 0.8 nm to 10 µm
( ) ( )( ) ( )
4242
42
42
42
,
,,,,,, 3*
2
SOHdepSOHSOH
cond
SOHnucgasSOH
CRRHCR
RHTNHCRnPTOHSORt
C
−+
+=∂
∂
( )( ) ( ) ( )idepSOHNcondjcoag
SOHnuci
NRRHCRRHNR
RHTNHCRt
N
i −++
=∂∂
,,
,,,
42
42 3
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Sulfuric Acid Nucleation Formation
SO2 + OH· + M → HOSO2· + MHOSO2· + O2 → HO2· + SO3(g)
SO3(g) + H2O + M → H2SO4(g) + MH2SO4(g) + nH2O(g) → H2SO4·nH2O(aq)
________________________________________________________________________________________
SO2(g) + OH· + O2 + (n+1)H2O → HO2· + H2SO4·nH2O(aq)
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Chemistry and deposition
Sulfuric acid is produced from the reaction of SO2 and OH1
Deposition:
vdep for aerosol dependent on particle size2, 1.0 cm/s used for H2SO4 3
]][[ 22 OHSOkR SOgas =
1kSO2 from DeMore et al. (1994)
Hcv
R iidrydep,=
3Brook et al. (1999)2Hummelshoj et al. (1992)
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Condensation
Condensation rate:
Change in number concentration:
Flux between fixed sections:
)()(2 0ppAKnFDDNJ pi −= π
42421 SOHiiSOHiiNcond CNFCNFR i −= −
( ) ( )[ ]33142
6ip
ip
pimtSOH
iDDRT
DKMF
−=
+ρπ
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Coagulation
Coagulation rate:
Generalized coagulation coefficient*
Linear interpolation to preserve mass, number:
2,21
1,
1, ≥−= ∑∑
∞
=−
=− kNKNNNKfR
jjjkkjkj
k
jjkjkcoag
( )( )βπ 212112 2 DDDDK pp ++=
kk
pkk VV
VVf
−
−=
+
+
1
1
kk
kpk VV
VVf
−
−=
++
11
*β calculated using method of Fuchs, (1964)
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Ternary nucleation correlation
Parameterization from Napari et al. (2002)Calculates nucleation rate using parameters of T, RH, NH3, H2SO4
Approximation for initial nuclei size dependent on nucleation rate and T1 nm under typical July conditions0.8 nm under typical January conditions
Approximation for composition of initial nuclei, also dependent on nucleation rate and T
Approximately 4 molecules of sulfuric acid, 4 of ammonium in July2 molecules of sulfuric acid, 2 of ammonium in January
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Nucleation rates
Presence of gas-phase ammonia necessary for nucleation in July
10 ppt generally enough
Both ammonia and sulfuric acid play important role in January
Cloud cover, weaker UV radiation limit production of sulfuric acid
1 2 3 40.1
1
10
100
Sulfuric acid concentration (ppt)
Am
mon
ia (p
pt)
0.01 0.1 10.1
1
10
100
Sulfuric acid concentration (ppt)
Am
mon
ia (p
pt)
July
January
10-5 10-3 10
-1
101 103
105 106
10-5 10-3
10-1
101 103
105 106
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Sensitivity to SO2 Emissions
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2
4
6
8
10
12
14
16
18
Day
s w
ith n
ucle
atio
n
Change in SO2 Concentration (%)
July
% o
f mod
eled
day
s
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10121416182022242628
Day
s w
ith n
ucle
atio
nChange in SO2 Concentration (%)
January
% o
f mod
eled
day
s
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Sensitivity to NH3 Emissions
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2
4
6
8
10
12
14
16
18
Day
s w
ith n
ucle
atio
n
Change in NH3 Concentration (%)
July
% o
f mod
eled
day
s
0102030405060708090100
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Day
s w
ith n
ucle
atio
n
Change in NH3 Concentration (%)
January
% o
f mod
eled
day
s
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Future Work
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Observational Analysis
Determine spatial extent of nucleation from “Supersite” 2001 observations and compare to SO2and NH3 maps.
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Observation-Model Hybrid
Prepare model-based predictions of seasonal nucleation frequency, timing, and growth rateCompare to previous (or new) measurements
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Vertical Profile Sampling
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Vertical Mixing Models
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Perturbed Real Air Samples
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Measurement technique
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60R
H
APSAPS
Dry sheath airfor Nafion dryers
Vent excessdry air1 LPM
RH
RH
LL -- DM
AD
MA
NN-- D
MA
DM
A
RH
HEPA MFHEPA
HEPA
RH
HEPAMFHEPA
HEPA
AmbientAir In
Dry AirExhaust
CPCCPC
CPCCPC
AmbientAir In
AerosolInlets
MF
Clean, Dry &Regulated Air
3-Way Plug Valvew/ Solenoid Actuator∆P Flowmeter
Ball Valve, Air Actuated
Mass Flow Meter
Bipolar Charger
Nafion DryerRotameter
DryDry--Ambient Aerosol Size SpectrometerAmbient Aerosol Size Spectrometer
Add RH controlled inlets (aerosol water measurement)Control & data acquisition hardware and software Data processing software to make 6 instruments behave like 1Extensive calibrationSynthesis with other instruments and web-based data visualization
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Scanning Mobility Particle Sizer
Condensation Particle
Counter (CPC)
Sheath Flow
AerosolIn Charger
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Scanning Mobility Particle Sizer
Condensation Particle
Counter (CPC)
Sheath Flow
AerosolIn Charger
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-
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Scanning Mobility Particle Sizer
Condensation Particle
Counter (CPC)
Sheath Flow
AerosolIn Charger
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Scanning Mobility Particle Sizer
Condensation Particle
Counter (CPC)
Sheath Flow
AerosolIn Charger
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Traffic and modeling
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Traffic Emission Sampling
1.E+03
1.E+04
1.E+05
1.E+06
1.E+07
0.001 0.01 0.1 1
Mobility Diameter (µm)
dN/d
log(
Dp)
, Dilu
tion
Cor
rect
ed (
cm-3
)
0.E+00
1.E+06
2.E+06
3.E+06
4.E+06
0.001 0.01 0.1 1
Log Scale Linear Scale
90thPercentile
10thPercentile
Note: 10th and 90th percentiles on 30-min average size distributions
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Total # Emission Factors for Vehicles
0
1E+16
2E+16
3E+16
> 95% CarsLow Speed
> 95% CarsHigh Speed
< 90% CarsHigh Speed
# / k
g fu
el
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“Spin-Off” of Modeling Techniques
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Calculation of gas-phase ammonia
Estimated from comparison of measured total NH3with PM2.5 SO4, NO3
When sufficient ammonia is available to neutralize these species, excess ammonia assumed to be in gas-phaseOtherwise, lower limit for parameterization used
Compared to equilibrium calculations using GFEMN for total NH3, NO3, and SO4
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Bondville
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0
10000
20000
30000
40000
50000
0:00 6:00 12:00 18:00 0:00
#/cc
-1
1
3
0:00 6:00 12:00 18:00 0:00
SO2 Concentration (ppb)
September 18, 2005CPC Particle Count (blue) vs. SMPS Particle Count (red)
Part
icle
Siz
e (n
m)
Res
pons
edN
/dlo
gDp
(cm
-3)
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Nucleation Box Model with May 2003 SWS Data
Constant NH3 of 1.5 µg m-3 (2200 ppt)Constant SO2 of 4 µg m-3 (1.54 ppb)Actual median RH and T from May datasetBright sun used for UV / OH calculation
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0 3 6 9 12 15 18 21 24
10
100
500
May Base Case
2.5
3
3.5
4
4.5
Part
icle
Siz
e (n
m)
Res
pons
edN
/dlo
gDp
(cm
-3)
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Mexico
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PM Background Info
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Typical Chemical Makeup
InorganicSaltsSO42-NO3-NH4+Na+Cl-
OrganicCompounds
Black Carbon
Metals