Dr. Tamer Alexan & Tina Liu on Secondary Particulate Concentration and Ammonia Levels at the EUEC2017: Energy, Utility & Environment Conference 2017

1. Secondary Particulate
Concentration and
Ammonia Levels
EUEC2017: Energy, Utility &
Environment Conference
San Diego, CA
Dr. Tamer Alexan & Tina Liu
February 9, 2017

2. Outline of Presentation
• Introduction
• Composition of PM2.5
• Role of atmospheric ammonia (NH3) in secondary PM2.5 (SPM) formation
• SPM assessment
• Objective
• Approach
• Assumptions
• Modeling
• Results
• Summary of findings

3. Introduction

4. Composition of PM2.5
Particulate Matter (PM) consists of solid and liquid particles.
Classification of
Particulate Matter
Description
Primary Emitted at the emissions source in particle form.
Secondary
Formed from a series of chemical and physical reactions
involving different precursor gases, such as SOx and
NOx, NH3 and ozone (O3) reacting to form sulphate,
nitrate and ammonium particulate matter.

5. 24%
13%
13%
27%
7%
10%
6%
Sulfate (secondary)
Nitrates (secondary)
Ammonium (secondary)
Organic Carbon (secondary)
Soil (primary)
Black Carbon (primary)
Other (primary/secondary)
Source: USEPA, https://www3.epa.gov/ttnchie1/conference/ei13/mobile/hodan.pdf
Composition of PM2.5

6. Source: Stauffer, W. 2016. Regulating particulate pollution: Novel analysis
yields new insights. Energy Futures, MIT Initiative.
O3
SPM Formation

7. SPM Assessment
Source: US EPA. 2014. Guidance for PM2.5 Permit Modeling. EPA-454/B-14-001. May 2014

8. Objective

9. Objectives
• How AERMOD and CALPUFF predict SPM
• Changes in SPM formation due to changes in background NH3 levels

10. Approach

11. Assumptions
• Emission rates and stack parameters taken from an existing Thermal Electric
Power Generation Plant
• Coal-fired plant with six generating units
• Capacity: 2,141 MW
• Total NOx Rate: 26,038 t/yr
• Total SO2 Rate: 26,379 t/yr
Stack Height (m) Diameter (m)
Exit Velocity
(m/s)
Exit
Temperature
(°C)
1 156 6.4 33.2 171.2
2 155.5 7.3 32.2 153.6
3 155.5 7.3 35.9 154

12. • Ozone (O3) and NH3 concentration from 5 stations in British Columbia
• Ozone (O3) concentrations
• Average: From five local stations over 12 months
• Seasonal: 3 month averages from five local stations
• Ammonia concentrations
• Average: From 5 local stations over 12 months
• Maximum: Maximum reported concentration of 5 local stations over 12
months
• Minimum : Minimum reported concentration of 5 local stations over 12
months
• Seasonal: 3 month averages from five local stations
Assumptions

13. Modeling
• 50 km x 50 km model
domain
• One year of prognostic
mesoscale
meteorological model
(MM5) data with
resolution of 4 km
• CALMET, resolution 1
km, produced in one
season
Model Domain (Red Outline)

14. Modeling
• SPM formation not accounted for by AERMOD
• CALPUFF used to estimate SPM ambient levels.
• Chemistry modules:
• MESOPUFF: SO2, SO4
+, NOx, HNO3, NO3
−
• RIVAD/ARM3: NO, NO2, NO2 NO3, SO2 NO3

15. • Modeled 6 cases based on background NH3 and O3 concentrations from measured
data in the model domain
Case Ammonia (NH3) Ozone (O3)
Case 1: Average Average Average
Case 2: Maximum Maximum Average
Case 3: Minimum Minimum Average
Case 4: Seasonal NH3 Seasonal Average
Case 5: Seasonal NH3 & O3 Seasonal Seasonal
Case 6: Default Model default Model default
Assumptions

16. • Background concentrations from measured data in the model domain
Case
Ammonia (NH3) [ppb,
µg/m3]
Ozone (O3) [ppb, µg/m3]
Case 1: Average 2.3, 1.6 16, 32
Case 2: Maximum 13, 9.1 16, 32
Case 3: Minimum 0.05, 0.04 16, 32
Case 4: Seasonal NH3 0.5-7.4, 0.3-5.2 16, 32
Case 5: Seasonal NH3 & O3
0.5-7.4, 0.3-5.2 9-24, 18-48
Case 6: Default 10, 7 10 , 20
Assumptions

17. 0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
0
5
10
15
20
25
30
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
AmmoniaConcentration(ppb)
OzoneConcentration(ppb)
Ozone and Ammonia Monthly Levels
Ozone
Ammonia
Assumptions

18. Results

19. Results
Average Maximum Minimum
Seasonal NH3 Seasonal NH3+O3 Default
4.0
3.0
2.0
1.0
0.9
0.8
0.7
0.6
0.5
Concentration(µg/m3)
Secondary PM2.5 24-Hour Concentrations

20. Advisian / 20
Seasonal NH3 Seasonal NH3+O3 Default
Average Maximum Minimum
1.0E-01
9.0E-02
8.0E-02
7.0E-02
5.0E-02
4.0E-02
3.0E-02
2.0E-02
1.0E-02
Concentration(µg/m3)
Secondary PM2.5 Annual Concentrations
Results

21. 0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0 5 10 15 20
Concentrations(µg/m3)
Distance from Source (km)
24-hour PM2.5 Concentrations
Average
Maximum
Minimum
Seasonal NH3
Seasonal O3+NH3
Default
Results

22. 0.0
0.5
1.0
1.5
2.0
2.5
0-5 km 5-10 km 10-15 km 15-20 km 20-25 km
Concentration(µg/m3)
Distance from Source (km)
Average 24-Hour PM2.5 Concentrations
Average
Maximum
Minimum
Seasonal NH3
Seasonal O3+NH3
Default
Results

23. 0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
0 5 10 15 20
Concentrations(µg/m3)
Distance from Source (km)
Annual PM2.5 Concentrations
Average
Maximum
Minimum
Seasonal NH3
Seasonal O3+NH3
Default
Results

24. 0.0E+00
2.0E-02
4.0E-02
6.0E-02
8.0E-02
1.0E-01
1.2E-01
1.4E-01
0-5 km 5-10 km 10-15 km 15-20 km 20-25 km
Concentration(µg/m3)
Distance from Source (km)
Average Annual PM2.5 Concentrations
Average
Maximum
Minimum
Seasonal NH3
Seasonal O3+NH3
Default
Results

25. -100
0
100
200
300
400
500
24 Hour Concentrations from Seasonal O3+NH3
Average Maximum
Minimum Seasonal NH3
Default
-100
0
100
200
300
400
500
0 5 10 15 20 25
Annual Concentrations from Seasonal O3+NH3
Distance from Source (km)
PercentChangeinConcentration
Results

26. Summary of Findings
• Ammonia in ambient air can react with NOx and SO2 to form
ammonium nitrate and ammonium sulphate, i.e. SPM
• AERMOD does not have the capability to predict SPM
• CALPUFF has 2 chemistry modules; RIVAD and MESOPUFF II
• Keeping O3 level constant there’s a direct relationship between NH3 and
SPM formation
• Using default NH3 and O3 levels provides overestimated SPM, which are
150 to 450% more than using seasonal NH3 and O3 levels
• Keeping O3 levels constant using an single average for SPM formation
can provide similar value if using variable seasonal O3 and NH3 levels
with season (between 9 and 25 percent less than using seasonal NH3
and O3 levels)Ozone has a significant role in SPM formation

27. Thank you.