Ammonia: Measurement role
in National Ambient Air
Networks
Rich Scheffe
Office of Air Quality Planning and Standards, U.S.
EPA
Acknowledgements
•
•
•
•
•
Brian Timin, EPA
Spyros Pandis, CMU
Jay Turner, Washington University
Eric Edgerton, ARA
Jim Homolya, EPA
Topics
• Role of NH3 in air quality management
• Overview of NH3/related measurements in
routine networks
• Measurement issues
• National Monitoring Strategy and
associated recommendations
NH3…effects
• Deposition
– watershed eutrophication
– Acidification/neutralization
• Global climate radiation budget (aerosol)
• National Air program standards
– PM10
– PM2.5
Regulatory Timetables
Further progress under the Clean Air Act is complex, burdensome and uncertain
NSR Permits for new sources & modifications that increase emissions
Designate 1-hr Severe Margareas for
Area
inal 8-hr
8-hr Ozone Attainment Ozone
NAAQS
Date
NAAQS
AttainNOx
ment
SIP
Date
Call
Ozone
1-hr Serious
Area Attainment
Date
OTC
NOx
Trading
99
NOx
SIPs
Due
00
01
Reductions
02
Mercury
Determination
Phase II
Acid Rain
Compliance
8-hr
Ozone
Attainment
Demonstration
SIPs due
03
04
Proposed
Utility
MACT
05
06
Final
Utility
MACT
Designate Areas
for Fine PM NAAQS
Interstate Transport Rule to Address
SO2/ NOx Emissions for Fine PM
NAAQS and Regional Haze
Acid Rain, PM2.5, Haze, Toxics
07
08
Note: Dotted lines indicate a range of possible dates.
Assess
Effectiveness
of Regional
Ozone
Strategies
Moderate
8-hr
Ozone
NAAQS
Attainment
Date
Possible
Regional NOx
Reductions ?
(SIP call II)1
09
10
Further action on ozone would be considered based
on the 2007 assessment.
2
The SIP-submittal and attainment dates are keyed off
the date of designation; for example, if PM or ozone are
designated in 2004, the first attainment date is 2009
EPA is required to update the new source performance
standards (NSPS) for boilers and turbines every 8 years
Serious 8-hr Ozone
NAAQS attainment
Date
11
12
Compliance
with Utility
MACT
New Fine PM NAAQS Latest attainment
Implementation Plans date for Fine PM
NAAQS 3
Regional Haze SIPs due
1
13
14
Compliance for
BART Sources
15
16
17
18
Compliance for BART
sources under the
Trading Program
Second Regional
Haze SIPs due
In developing the timeline of current CAA requirements,
it was necessary for EPA to make assumptions about
rulemakings that have not been completed or, in some
case, not even started. EPA’s rulemakings will be
conducted through the usual notice-and-comment
process, and the conclusions may vary from these
assumptions.
Complex system
• Measurements
– Stability/volatility
• Ammonium nitrate, association with nitric acid (sticky)
– Real exposure indoors?...given volatility?
• Consequently, NH4, NH3g, HNO3g all present challenges
• Uncertain emission estimates
– Diversity of area sources
– Many agricultural based
• Modeling confounded by heterogeneous processes
and above (i.e., ability to diagnose)
NH3 is not a “central” player in atmospheric chemistry; however, various
inter-pollutant interactions impact pollutant/component specific
strategies?
Figure 4. Linkage between oxidant chemistry and
fine particle (FP) formation.
Nighttime N2O5
Chemistry
PAN
N2O5
O3
hv
HONO
hv
·NO3
3
OP
1
OD
HOOH
HNO3
hv
HO
2
hv
NO
NO2
NH3
·OH
SOx
VOC
CO
H2SO4
Radical Pool
HO2·; RO2·
Carbonyls
Source
Secondary
Sink
hv
SOx
Clouds/Aqueous
NH4NO3
FP
org
aer
Consequently,
Impacts on major aerosol components
due to precursor reductions…confusing!
NOx
SOx
VOC/CO
Nitrate
↕
↑
↕
Sulfate
↕
↓
↕
Ozone
↕
↕
↓
Organic
Carbon
?
?
↓
Reductions of
→
Is NH3 limiting
…..in formation of ammoniumnitrate?
• Or, where and when are are NOx
controls most effective in reducing pNO3?
Limiting Reactant: Ammonia or Nitric Acid
(courtesy, Pandis, CMU)?
Total Nitric Acid (mg m-3)
Ammonium Nitrate (mg m-3)
80
A
60
A:Ammonia limited
50
40
30
20
B: Nitric acid limited
B
10
0
0
10
20
30
Total Ammonia (mg m-3)
40
The Sulfuric Acid/Ammonia System
2001…courtesy, Pandis, CMU
Concentration (mg m-3)
2 Ammonia:1 Sulfate
20
18
16
14
12
10
8
6
4
2
0
Ammonia
Ammonium
Sulfate
Bisulfate
Sulfuric acid
0
1
2
3
3.6
5
Total Available Ammonia (mg m-3)
10
Model Sensitivity Runs
• When/where are Nox controls most
effective?
• Impact on nitrates associated with
SO2 and VOC reductions
CMAQ Ammonia Sensitivity Runs50% NH3 Reduction- January
Basecase Nitrate
Nitrate with 50% Ammonia
Reduction
50% NOx Reduction- January
Effect on Sulfate and Nitrate
50% NOx Reduction- Reduced NH3 base (50% NH3 reduction)- January
effect on Sulfate and Nitrate
50% SO2 Reduction- July
Effect on Sulfate and Nitrate
50% SO2 Reduction- January
Effect on Sulfate and Nitrate
Seasonal Average IMPROVE
Nitrate
Seasonal Average Particulate Nitrate- IMPROVE
and CASTNET Visibility Network*
10
CM AQ Predictions (ug/m3)
9
8
7
Summer
6
Fall
Spring
5
Winter
4
3
2
1
0
0
1
2
*CASTNET Visibility netw ork data
is for 8 sites- fall only
3
4
5
6
7
8
Improve Observations (ug/m3)
9
10
Where are the measurements?
• Ammonium (Dry)....PM2.5 speciation (including IMPROVE);
CASTNET
• Ammonium Wet (NADP)
• NH3….SEARCH/ARIES…..network
• Special studies (PM2.5 Supersites)
Current/Planned
Urban & Rural PM2.5 Speciation Networks
SS
SS
SS
SS
SS
SS
Trends (54)
Supplemental (~215 sites currently known)
SS Supersites
Daily Sites
IMPROVE
IMPROVE Protocol
Castnet conversion
SS
Deploy in 2002
Deploy in 2003
01/02
SEARCH Enhanced Air Quality Measurement Network
rural
urban
suburban
Yorkville (YRK)
North Birmingham (BHM)
Jefferson Street (JST)
Centreville (CTR)
Oak Grove (OAK)
Outer Landing Field #8 (OLF)
Gulfport (GFP)
Pensacola (PNS)
CASTNET NH4…1992
CASTNET NH4…2002
Measurement Issues, NH3
• Integrated methods
– Absorption, extraction, analysis
• CASTNET filter pack/denuder system (1 week)
• Acid denuders in low volume particle samplers (typically 24
hr.)
– Labor intensive, lack temporal detail
• Semi-continuous methods
–
–
–
–
Cycled difference techniques
IC particle/gas methods
Optical techniques (FTIR, DOAS)
Cost, familiarity, reliability, commercial availability
Measurement Issues, NH4
• PM2.5 speciation networks
– 24 hr. integrated measurement; 1/3 day
– 54 trends sites; ~200 SIP sites
• Acid gas denuding; nylon (basic) filter
substarte
– small subset of IMPROVE sites
• Acid/base gas denuding; nylon (basic) filter
substrate…traps NO3 loss…what about NH3
loss?
Recent Example Applications
• St. Louis Supersite (Integrated)
• Search/ARIES…ARA (continuous)
Daily 24-Hour Integrated Ammonia: St. Louis
Urban/Rural Contrast (Aug-Nov 2001)..courtesy of Jay Turner, Washington
University
14
Park Hills, MO (90 km south of St. Louis)
12
East St. Louis, IL (3km east of City of St. Louis, MO, central business district)
Ammonia Concentration (ppb)
10
8
6
4
2
0
08/17/01
08/27/01
09/06/01
09/16/01
09/26/01
10/06/01
10/16/01
10/26/01
11/05/01
11/15/01
11/25/01
Yorkville, GA SEARCH Site (courtesy,
ARA..Edgerton)
Met
Particle
analyzers
Trace gases
Lat. 33.95 N
Long. 85.01 W
Elev. 390 m
Instrumentation
• 10 meter met
• Trace gas: O3, CO, SO2, NO, NO2(photolytic),
HNO3, NOy
• Filter PM 2.5: FRM Mass, Particle Composition
Monitor (PCM) Speciation Monitor
• Filter PM Coarse Mass (Dichot)
• Semi-Continuous PM: Nephelometer,
Aethelometer, R&P 5400, Harvard SO4, ARA
NO3/NH4, Dried 30°C TEOM
TRN Diagram
TRN NH3 vs Denuder NH3
24 Hour Samples
8.0
7.0
Continuous NH3 = 1.12 Denuder NH3 - 0.19
R2 = 0.92
Continuous NH3, ug/m3
6.0
5.0
4.0
3.0
2.0
1.0
0.0
-1.0
0.0
1.0
2.0
3.0
4.0
Denuder NH3, ug/m3
5.0
6.0
7.0
HNO3
NH4
NO3
NH3
9/27/03 18:00
9/27/03 12:00
9/27/03 6:00
9/27/03 0:00
9/26/03 18:00
9/26/03 12:00
9/26/03 6:00
9/26/03 0:00
9/25/03 18:00
9/25/03 12:00
9/25/03 6:00
9/25/03 0:00
9/24/03 18:00
9/24/03 12:00
9/24/03 6:00
9/24/03 0:00
[HNO3] ppbv [NO3] ug/m3,[NH4] ug/m3
10.0
50.0
9.0
45.0
8.0
40.0
7.0
35.0
6.0
30.0
5.0
25.0
4.0
20.0
3.0
15.0
2.0
10.0
1.0
5.0
0.0
0.0
[NH3], ppbv
HNO3, NH3, NH4NO3 events
9/
12
/0
9/ 3
13
/0
9/ 3
14
/0
9/ 3
15
/0
9/ 3
16
/0
9/ 3
17
/0
9/ 3
18
/0
9/ 3
19
/0
9/ 3
20
/0
9/ 3
21
/0
9/ 3
22
/0
9/ 3
23
/0
9/ 3
24
/0
9/ 3
25
/0
9/ 3
26
/0
9/ 3
27
/0
9/ 3
28
/0
9/ 3
29
/0
9/ 3
30
/0
3
[NO], [NO2], [HNO3], [NOy], ppbv
NOy Budget Time-Series
40.0
35.0
30.0
25.0
20.0
15.0
10.0
5.0
0.0
NO
NO2
NOy
HNO3
What should we do?
• New National Monitoring Strategy
• NCORE multiple pollutant stations
• Emphasis on more science based
measurements, model evaluation, long term
program accountability
National Core Network: NCORE
•
Goal: Move from loosely tied single-pollutant networks to
coordinated, highly leveraged multi-pollutant networks with real
time reporting capability
SO2
PM
PM
PAMS
PM
CO
O3
O3
Toxics
PM
IMPROVE
CASTNET
NCore Measurements
Level 2: ~ 75 Multipollutant (MP)
Sites,“Core Species”
Plus Leveraging From
PAMS,
Speciation Program,
Air Toxics
L1
Level 1. 3-10 Master
Sites Comprehensive
Measurements,
Advance Methods
Serving Science and
Technology Transfer
Needs
L2
Level 3
Minimum “Core” Level 2 Measurements
Continuous N,SO2,CO, PM2.5, PM10, O3; PM2.5
FRM, Meteorology (T,RH,WS,WD)…NH3, HNO3
at subset?
Level 3: Single
Pollutant Sites
(e.g.> 500 sites
each for O3 and
PM2.5
Mapping Support