Transcript PM 2.5 (mg/m 3 ) - Carnegie Mellon University

Atmospheric Aerosol
From the Source to the Receptor
Insights from the Pittsburgh Supersite
Spyros Pandis, Allen Robinson, and Cliff Davidson
Department of Engineering and Public Policy
Carnegie Mellon University
Fine Particles
Coarse Particles
Aerosol Size Distribution
Ultrafine Particles
Number
(dN/dlogDp), cm-3x103
40
30
Nucleation
Mode
20
Aitken
Mode
10
Volume
(dV/dlogDp), m3/cm3
0
40
Droplet
Submode
Accumulation
Mode
30
20
Coarse
Mode
Condensation
Submode
10
0
0.01
0.1
1
Diameter (micrometers)
10
Air Pollution in Pittsburgh
USX Tower
July 2, 2001
PM2.5=4 g m3
July 18, 2001
PM2.5=45 g m3
FRM PM2.5 Concentrations
During PAQS
64
Study Average: 17 µg/m3
60
56
PM2.5 (µg/m3)
52
48
44
40
36
32
28
24
20
16
12
8
4
0
29-Jun
18-Aug
7-Oct
2001
26-Nov
15-Jan
6-Mar
2002
25-Apr
14-Jun
Fine PM Composition
35
PM2.5 mass
Organic matter
Elemental carbon
Sulfate
Nitrate
Ammonium
Crustal components
PM2.5 (g/m3)
30
25
20
15
10
5
0
Jul
Aug
Sep
Oct
2001
Nov
Dec
Jan
Feb
Mar
2002
Apr May
Jun
PM2.5 Mass Balance
(July and August 2001)
Crustal
60
EC
50
Ammonium
Nitrate
40
Sulfate
Organics
30
20
10
12
19
August
8/26/01
8/19/01
5
8/12/01
29
8/5/01
22
7/29/01
15
July
7/22/01
8
7/15/01
1
7/8/01
0
7/1/01
PM2.5 (µg/m3)
70
26
Mass Balance Closure – July 2001
Water
Crustal
NO3
SO4
NH4
EC
OC*1.8
FRM
PM2.5 (g m-3)
60
50
40
30
20
10
0
1
4
7
10
13
16
19
22
25
28
Date (July 2001)
Good mass balance was achieved for the winter months
31
Satellite Sites Outside Pittsburgh
Steubenville
Florence
Greensburg
Holbrook
Athens
Sulfate Mass at Main Site and Satellite Sites
PM 2.5 sulfate
Florence
Greensburg
30.0
Hazelw ood (PIT)
Law renceville (PIT)
20.0
10.0
7/
10
/0
1
7/
12
/0
1
7/
14
/0
1
7/
16
/0
1
7/
18
/0
1
7/
20
/0
1
7/
22
/0
1
7/
24
/0
1
7/
26
/0
1
7/
28
/0
1
7/
30
/0
1
7/
8/
01
7/
6/
01
7/
4/
01
7/
2/
01
0.0
6/
30
/0
1
PM2.5 sulfate, ug/m^3
Main site (PIT)
Date
Continuous Sulfate Measurements
and Long Range Transport
Pittsburgh
Decrease after
a front passed,
wind speeds
decreased, and
some rain fell
PM2.5

Increase as
winds shift
direction
12:00 EST
80
3

July 26, 2002
(16.2 g m-3)
PM2.5 sulfate (g/m ) 3
Sulfate (g/m )

0:00 EST
60
40
20
0
0:00
6:00
12:00
Hour (EST)
18:00
24:00
The Source-Receptor Challenge: Interactions
between Fine PM and Their Precursors
40
Concentration
35
30
Crustal
Ammonium
EC
Primary Inorganic PM emissions
NH3 emissions
25
20
Organics
Primary Organic emissions
15
10
5
VOC emissions
Sulfate
SO2 emissions
Nitrate
0
PM2.5 Composition during the Winter
NOx emissions
Ammonium Nitrate Formation

The formation of ammonium nitrate requires

Nitric acid (major sources of NOx in the US are transportation and
power plants)


The formation reaction is favored at:



Free ammonia (ammonia not taken up by sulfate)
Low temperatures (night, winter, fall, spring)
High relative humidity
Hypothesis: A significant fraction of the sulfate reduced will
be replaced by nitrate when SO2 emissions are reduced.
Modeling Nitrate Partitioning
8
observed
predicted
3
Aerosol Nitrate (g/m )
3
sol Nitrate (g/m )
Aerosol Nitrate (g m-3)
6
Summer
4
2
0
7/1
10
8
7/3
7/5
7/7
7/9
7/11
observed
predicted
8
6
6
4
4
2
2
0
0
7/14
1/3
10
7/13
Winter
7/16
1/5
7/18
1/7
7/20
1/9
7/22
1/11
Date
Date
7/24
1/13
7/26
1/15
7/28
1/17
Effect of Sulfate Concentration
Changes on Inorganic PM2.5
Inorganic PM2.5 (g m-3)
14
Sulfate
Ammonium
Nitrate
12
10
8
6
4
2
0
Base
Case
10%
20%
30%
Sulfate Reduction
40%
50%
Reductions of Sulfuric and Nitric Acid
(Pittsburgh, July 2001)
Inorganic PM2.5 Reduction (%)
30
20
-50% Nitric Acid
10
Same Nitric Acid
0
0
10
20
Sulfate Reduction (%)
30
Reductions in Ammonia
(July 2001)
Inorganic PM2.5 Reduction (%)
20% Sulfate Reduction
40
30
20
10
0
0
10
20
30
40
Ammonia Reduction (%)
50
Reducing Inorganic PM2.5
Using an observation-based model:
 Controls of SO2 will reduce sulfate and PM2.5 in all
seasons.
 A fraction of the now existing sulfate will be
replaced by nitrate.
 The lifetime of nitrate will increase during the
summer because it will move from the gas to the
aerosol phase
 For Pittsburgh, ammonia controls in all seasons can
minimize the replacement of sulfate by nitrate.
 For Pittsburgh, NOx controls will help reduce the
nitrate during the winter but they will have a small
effect during the summer.
Source Apportionment of Organic
Aerosol
Primary
Organic
Aerosol
Anthropogenic
•Gasoline
•Diesel
•Woodsmoke
•Meat Cooking
Biogenic
Secondary
Anthropogenic
•Aromatic VOCs
Biogenic
•Terpenes
OC and EC Measurements
10
OC
OC and EC (g C/m3)
9
EC
8
7
6
5
4
3
2
1
0
1
3
5
7
9
11
13
July
15
17
19
21
23
25
27
29
31
2
4
August
•Use of 3 samplers (TQQQ, denuder-based, semi-continuous)
•Five sets of measurements for EC-OC
Ozone as indicator of SOA Production
120
18
16
100
Ozone
OC/EC Ratio
14
80
12
10
60
8
40
6
4
20
2
0
15-Jul
16-Jul
17-Jul
18-Jul
19-Jul
20-Jul
0
21-Jul
O3 (ppb)
OC/EC Ratio (front quartz)
20
Daily Averaged OC Composition
(July 2001)
OC (gC/m3)
10
8
Secondary
6
4
Primary
2
0
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 2
July
August
Monthly Average SOA
50
SOA (% OC)
40
30
20
10
0
Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul
2001
2002
Primary Biogenic Contribution
Summer 01: Carbohydrate 36% of OM
10
9
9
8
8
OC x 1.8
7
PM2.5 (ug/m3)
7
PM2.5 (ug/m3)
Winter 02: Carbohydrate 12% of OM
10
6
5
4
5
4
3
3
2
2
1
Carbohydrate
0
6/23/01
7/3/01
OC x 1.8
6
Carbohydrate
1
7/13/01
7/23/01
8/2/01
8/12/01
0
12/26/01
1/5/02
1/15/02
1/25/02
2/4/02
2/14/02
18
Tracers for Woodsmoke
16
Hydroxy-/Methoxy-Phenols
Levoglucosan
200
14
12
10
150
8
100
6
4
50
2
0
0
4
8
Tracers for Vehicle Emissions
3
Hopanes
6
2
4
1
2
0
0
Sum
Fall
Win
Spr Sum
Alkylcyclohexanes (ng/m3)
Alkylcyclohexanes (C19-C25)
Hopanes (ng/m3)
Levoglucosan (ng/m3)
250
Hydroxy Methoxy Phenols (ng/m3)
300
Fence Line Sampling to Characterize
Emissions from Coke Facility
285o
Sampling Site
225o
Sampling
Site
Coke Works
~ 3 miles long
N
Coke
Works Monongahela
Road
River
175o
~1/4 mile
“Fingerprinting” a Coke Processing Plant
8
Atm. Conc (ng/m3)
Cr
6
4
2
0
-2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Cd
Atm. Conc (ng/m3)
Atm. Conc (ng/m3)
8/21/02
8/21/02
8/22/02
Sampling Date
200
180
160
140
120
100
80
60
40
20
0
8/22/02
Sampling Date
Zn
8/21/02
8/22/02
Sampling Date
Looking at Single Particles from
the Coke Facility
Single Particle Mass Spectrometry
(Wexler, UC Davis)
1.0
Class Vector 000000 Fraction of total particles: 0.8111 Average total signal: 74.72mV
0.8
C+
C3H8N+
0.6
Alkyl Amines
(81% of particles)
NH+
0.4
CH4N+
C2H6N+
C4H10N+
C5H12N+
0.2
0.0
10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95
Iron and Cerium Class from Steel Facility
60o
Coal Power
o
293 , Coal Steam
0.6
N
Fe+
0.5
CeO+
303o Coke &
Cement
0.4
Supersite
137o, Steel
0.3
0.2
245o, Glass
FeO, Ce+2
CeO2+
241o, Steel
0.1
0.0
163o
Steel
174o
Coal Power
50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180
m/z
14
0.6
168o
Coke
140o
o12
PM2.5 Emissi
10-100 t/
101-500 t/
> 500 t/yr
10 miles
192
10
Coal Power
Normalized particle fraction
Normalized fraction
Integrated Ion Current
Ce+
0.5
0.4
0.3
0.2
8
6
4
0.1
2
0
55
65
120
170
200
320
600
Particle diameter (nm)
1040
1620
0
0
20
40
60
80 100 120 140 160 180 200 220 240 260 280 300 320 340
Wind Direction: azimuth angle
Wind Direction
Typical PM Size Distribution Evolution
August 10, 2001
Nucleation and Growth a Few
Hours After Sunrise
Nucleation and Visibility
USX Tower
USX Tower
Fraction of
Days With Nucleation
Nucleation Frequency
> 1-hr Duration
< 1-hr Duration
None
100%
50%
0%
Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
2001
2002
Significant fraction of days (30%)
 Most prevalent in spring, fall

Aerosol Number and Mass
20x104
200000
Pittsburgh, PA
2001-2002
Number (#/cm3)
150000
100000
10x104
50000
Aerosol Mass (μg/m3)
0
0

25
50
PM2.5 (g m-3)
75
100
Negative correlation related to nucleation activity
Composition of 10-60 nm Particles
(Jimenez, U. Colorado and Worsnop, Aerodyne)
Mass Fraction (10-60 nm Particles) Aerosol Mass Spectrometer*
Nitrate
100%
100%
Mass Fraction
10-60 nm
Ammonium
75%
Sulfate
Organics
50%
50%
25%
Particle Size (nm)
0%
0%
500
1
3
5
7
9
11
13
15
17
19
21
23
100
10
00:00
06:00
12:00
18:00
24:00
*Zhang & Jimenez (Univ. Colorado-Boulder)
Nucleation Model Evaluation (July 27, 2001)
Measured
Predicted
Nucleation and Ultrafine Particles


The model was successful in reproducing the
observed behavior (nucleation or lack of) in all
simulated dates in July (10) and January (10)
Strong evidence that the nuclei are sulfuric
acid/ammonium/water clusters


Discrepancies in the nucleation rates


Growth with the help of organics
the model tends to predict higher rates
Ammonia appears to be the controlling reactant !

Small to modest reductions of ammonia can turn off the
nucleation in the area especially during the summer
PMCAMx+ Modeling Domain
July 12, 2001
•
•
•
•
PM2.5 Sulfate
July 17, 2001
36x36 km grid, 14 levels up to 6 km
10 aerosol sections, 13 aerosol species
20 million differential equations
8 CPU hours on a PC per simulation day (EQUIlibrium module)
PM2.5 Sulfate Simulation
(July 2001)
SOA Simulation (July 2001)
Anthropogenic
Biogenic
PMCAMx+ Evaluation in Pittsburgh
7/13
7/14
7/15
7/16
7/17
7/18
PM2.5
80
7/12
10
PM2.5 NO3 [ug/m3]
7/12
100
60
40
20
7/13
7/14
8
7/15
7/16
7/17
7/18
Nitrate
6
4
2
0
0
0
24
48
72
96
120
144
0
168
40
Sulfate
30
20
10
24
48
72
96
120
144
168
144
168
15
PM2.5 Total NH3 [ug/m3]
50
12
Ammonium
9
6
3
0
0
48
PM2.5 OC [ug/m3]
24
72
96
Simulation Hours
7/12
144
120
15
7/13
168
7/14
7/15
0
7/17
7/16
24
7/18
48
OM
12
9
6
3
0
0
24
48
10
PM2.5 EC [ug/m3]
0
72
96
120
144
168
96
120
144
168
EC
8
6
4
2
0
0
24
48
72
Simulation Hours
72
96
Simulation Hours
120
Predicted vs. Estimated in Pittsburgh
(Primary and Secondary OA)
7/12
Predicted [g/m3]
15
7/13
7/14
7/15
7/16
7/17
7/18
Secondary
12
Primary
9
6
3
0
0
24
48
72
96
120
144
168
0
24
48
72
96
120
144
168
Estimated [g/m3]
15
12
9
6
3
0
Simulation Hours
• EC Tracer Method (Cabada et al., 2003)
PM2.5 Response (%)
to 30% SO2 Emission Reduction
July 18, 2001
90
Concentration Change (g m-3)
90
Percent Change
30
12
25
10
20
8
15
6
10
4
5
2
1
1
97
0
1
1
97
0
Conclusions

Water is retained in the FRM filters during the days with high
sulfate and acidity



Large regional contributions for both sulfate and organics
Development of observation based model for the substitution of
sulfate by nitrate (requires nitric acid and ammonia
measurements)




The water can be estimated with a thermodynamic model and it
will decrease as sulfate decreases
SO2 reductions will reduce sulfate and PM2.5 but nitrate will also
increase in all seasons
Ammonia reductions can prevent the nitrate increase
NOx reductions can help during the winter
Organic aerosol sources:



Roughly 30-40% of the organic PM is secondary during the
summer (higher in worst days) and around 10% during the winter.
Evidence for significant primary biogenic PM during the summer
(around 30%)
Transportation and biomass burning are the other significant
sources in the area
Conclusions (continued)


New technologies (Single Particle Mass Spectrometry,
semi-continuous metal measurements) allow the
fingerprinting of point sources.
Frequent nucleation events (around 100 per year)






At low PM concentrations
Sunlight
Evidence for regional scale (100-300 km)
Sulfuric acid/ammonia/water nuclei
Ammonia appears to be the limiting reactant for most events
Supersite data together with the results from other studies
and networks will allow us to evaluate our understanding
of atmospheric PM in the US


First results of PMCAMx for summer 2001 are encouraging
Consistency between 3D CTM results and observation based
models for nitrate and SOA.