Secondary Particulate Concentration and Ammonia Levels

EUEC2017: Energy, Utility &

Environment Conference

San Diego, CA

Dr. Tamer Alexan & Tina Liu

February 9, 2017

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

Introduction

Composition of PM2.5

Particulate Matter (PM) consists of solid and liquid particles.

Classification of

Particulate MatterDescription

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.

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

Source: Stauffer, W. 2016. Regulating particulate pollution: Novel analysis

yields new insights. Energy Futures, MIT Initiative.

O3

SPM Formation

SPM Assessment

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

Objective

Objectives

• How AERMOD and CALPUFF predict SPM

• Changes in SPM formation due to changes in background NH3 levels

Approach

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

• 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

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)

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

• 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

• Background concentrations from measured data in the model domain

CaseAmmonia (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

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

Am

mo

nia

Co

nce

ntr

ati

on

(p

pb

)

Ozo

ne C

on

cen

trati

on

(p

pb

)

Ozone and Ammonia Monthly Levels

Ozone

Ammonia

Assumptions

Results

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

Co

nce

ntra

tion

(µg

/m3)

Secondary PM2.5 24-Hour Concentrations

Advisian / 20

Seasonal NH3 Seasonal NH3+O3 Default

Average Maximum Minimum1.0E-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

Co

nce

ntra

tion

(µg

/m3)

Secondary PM2.5 Annual Concentrations

Results

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

Co

nce

ntr

ati

on

s (µ

g/m

3)

Distance from Source (km)

24-hour PM2.5 Concentrations

Average

Maximum

Minimum

Seasonal NH3

Seasonal O3+NH3

Default

Results

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

Co

nce

ntr

ati

on

(µ

g/m

3)

Distance from Source (km)

Average 24-Hour PM2.5 Concentrations

Average

Maximum

Minimum

Seasonal NH3

Seasonal O3+NH3

Default

Results

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

Co

nce

ntr

ati

on

s (µ

g/m

3)

Distance from Source (km)

Annual PM2.5 Concentrations

Average

Maximum

Minimum

Seasonal NH3

Seasonal O3+NH3

Default

Results

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

Co

nce

ntr

ati

on

(µ

g/m

3)

Distance from Source (km)

Average Annual PM2.5 Concentrations

Average

Maximum

Minimum

Seasonal NH3

Seasonal O3+NH3

Default

Results

-100

0

100

200

300

400

50024 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)

Perc

en

t C

han

ge i

n C

on

cen

trati

on

Results

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

Thank you.