Ammonia: Measurement role in National Ambient Air
NetworksRich 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
Phase IIAcid Rain
Compliance
MercuryDetermination
ProposedUtilityMACT
New Fine PM NAAQSImplementation Plans
Designate Areasfor Fine PM NAAQS
Ozone
Acid Rain, PM2.5, Haze, Toxics
1-hr Severe Area
Attainment Date
Compliance for BART Sources
NSR Permits for new sources & modifications that increase emissions
99 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17
OTC NOx
Trading
1-hr Serious Area Attainment
Date
NOx
SIPs Due
Designate areas for8-hr Ozone NAAQS
NOx
SIP CallRed-uc-tions
00 18
FinalUtilityMACT
Compliancewith Utility MACT
Assess Effectiveness of Regional Ozone Strategies
Regional Haze SIPs due
Latest attainmentdate for Fine PM
NAAQS 3
Compliance for BART sources under the Trading Program
Second Regional Haze SIPs due
Marg-inal 8-hr Ozone
NAAQS Attain-ment Date Possible
Regional NOx
Reductions ?(SIP call II)1
Interstate Transport Rule to Address SO2/ NOx Emissions for Fine PM NAAQS and Regional Haze
Note: Dotted lines indicate a range of possible dates.
1 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
Moderate 8-hr Ozone NAAQS AttainmentDate
8-hrOzone Attain-mentDemon-stration 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.
Further progress under the Clean Air Act is complex, burdensome and uncertain
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?fine particle (FP) formation.
·OH
O3
HONO
VOC
Radical PoolHO2·; RO2·
Carbonyls
NO
HNO3
FP
NO2
SOx
H2SO4
NH3
HOOH
hv
hv
CO
hv
SOx
Clouds/Aqueous
orgaer
Source
Secondary
Sink
PAN N2O5
Nighttime N2O5
·NO3
Chemistry
H O2
hv
O1
D
O3
P
hv
Figure 4. Linkage between oxidant chemistry and
NH4NO3
Organic Carbon
Ozone
Sulfate
Nitrate
Reductions of?
Impacts on major aerosol components due to precursor reductions…confusing!
???
???
???
???
VOC/COSOxNOx
Consequently,
Is NH3 limiting…..in formation of ammoniumnitrate?
• Or, where and when are are NOxcontrols most effective in reducing p-NO3?
Limiting Reactant: Ammonia or Nitric Acid(courtesy, Pandis, CMU)?
0 10 20 30 40
0
20
40
60
80
10
30
50
Ammonium Nitrate (µg m-3)
Tota
l Nitr
ic A
cid
(µg
m-3
)
Total Ammonia (µg m-3)
A
B
A:Ammonia limited
B: Nitric acid limited
The Sulfuric Acid/Ammonia System 2001…courtesy, Pandis, CMU
02468
101214161820
0 1 2 3 3.6 5 10
AmmoniaAmmoniumSulfateBisulfateSulfuric acid
Total Available Ammonia (µg m-3)
Co
nce
ntr
atio
n (µ
g m
-3)
2 Ammonia:1 Sulfate
Model Sensitivity Runs
• When/where are Nox controls most effective?
• Impact on nitrates associated with SO2 and VOC reductions
CMAQ Ammonia Sensitivity Runs-50% NH3 Reduction- January
Basecase Nitrate Nitrate with 50% Ammonia Reduction
Seasonal Average IMPROVE Nitrate
Seasonal Average Particulate Nitrate- IMPROVEand CASTNET Visibility Network*
0
1
2
3
4
5
6
7
8
9
10
0 1 2 3 4 5 6 7 8 9 10
Improve Observations (ug/m3)
CM
AQ
Pre
dic
tio
ns
(ug
/m3)
Summer
Fall
Spring
Winter
*CASTNET Visibility network data is for 8 sites- fall only
Where are the measurements?• Ammonium (Dry)....PM2.5 speciation (including IMPROVE);
CASTNET
• Ammonium Wet (NADP)
• NH3….SEARCH/ARIES…..network
• Special studies (PM2.5 Supersites)
Trends (54)Supplemental (~215 sites currently known)SupersitesDaily Sites IMPROVEIMPROVE Protocol Castnet conversion Deploy in 2002 Deploy in 2003
Current/Planned Urban & Rural PM2.5 Speciation Networks
SS SS
SS
01/02
SS
SS
SS
SS
SS
SEARCH Enhanced Air Quality Measurement Network
Oak Grove (OAK)
Centreville (CTR)
Pensacola (PNS)
Yorkville (YRK)
Jefferson Street (JST)
North Birmingham (BHM)
Gulfport (GFP)
Outer Landing Field #8 (OLF)
rural urban suburban
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?
Daily 24-Hour Integrated Ammonia: St. LouisUrban/Rural Contrast (Aug-Nov 2001)..courtesy of Jay Turner, Washington
University
0
2
4
6
8
10
12
14
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
Am
mon
ia C
once
ntra
tion
(ppb
)
Park Hills, MO (90 km south of St. Louis)
East St. Louis, IL (3km east of City of St. Louis, MO, central business district)
Lat. 33.95 NLong. 85.01 WElev. 390 m
Trace gasesMet
Particleanalyzers
Yorkville, GA SEARCH Site (courtesy, ARA..Edgerton)
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 NH3 vs Denuder NH324 Hour Samples
Continuous NH3 = 1.12 Denuder NH3 - 0.19R2 = 0.92
-1.0
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0
Denuder NH3, ug/m3
Con
tinu
ous
NH
3, ug
/m3
HNO3, NH3, NH4NO3 events
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.09/
24/0
3 0:
00
9/24
/03
6:00
9/24
/03
12:0
0
9/24
/03
18:0
0
9/25
/03
0:00
9/25
/03
6:00
9/25
/03
12:0
0
9/25
/03
18:0
0
9/26
/03
0:00
9/26
/03
6:00
9/26
/03
12:0
0
9/26
/03
18:0
0
9/27
/03
0:00
9/27
/03
6:00
9/27
/03
12:0
0
9/27
/03
18:0
0
[HN
O3]
ppb
v [N
O3]
ug/
m3,
[NH
4] u
g/m
3
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
45.0
50.0
[NH
3], p
pbv
HNO3 NH4 NO3 NH3
NOy Budget Time-Series
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
9/12/0
39/1
3/03
9/14/0
39/1
5/03
9/16/0
39/1
7/03
9/18/0
39/1
9/03
9/20/0
39/2
1/03
9/22/0
39/2
3/03
9/24/0
39/2
5/03
9/26/0
39/2
7/03
9/28/0
39/2
9/03
9/30/0
3
[NO
], [N
O2]
, [H
NO
3], [
NO
y], p
pbv
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
PAMSPM
O3
O3
PM
PM
SO2
Toxics
PM
CO
IMPROVECASTNET
Level 2: ~ 75 Multi-pollutant (MP)
Sites,“Core Species” Plus Leveraging From
PAMS, Speciation Program,
Air Toxics
Level 1. 3-10 Master Sites Comprehensive
Measurements, Advance Methods
Serving Science and Technology Transfer
Needs
Level 3: Single Pollutant Sites (e.g.> 500 sites each for O3 and
PM2.5 Mapping Support
L2
Level 3
L1
NCore Measurements
Minimum “Core” Level 2 MeasurementsContinuous N,SO2,CO, PM2.5, PM10, O3; PM2.5 FRM, Meteorology (T,RH,WS,WD)…NH3, HNO3 at subset?