Mark S. Zahniser
Urban Ammonia Source Characterization Using
Infrared Quantum Cascade Laser Spectroscopy
NADP Ammonia WorkshopOctober 2003
AERODYNE RESEARCH, Inc.
NH3 DETECTION WITHINFRARED SPECTROSCOPY
Strong infrared absorber high sensitivity Distinct absorption lines high selectivity Known molecular properties absolute
concentrations without calibration standardsBeer’s Law: A = N l
Methods:– Fourier Transform Infrared (FTIR)– Photoacoustic detection with CO2 laser (PA)– Tunable Infrared Laser Absorption (TILDAS)
» Near-IR » Mid-IR
• Lead-salt diode lasers (cryogenic cooling)• Quantum Cascade Lasers (new- TE cooling)
Cryogen-Free Pulsed QC Lasers
ADVANTAGES: Decreased Instrument Size and Weight Improved Laser Mode Stability Unattended Remote Monitoring “Turn-Key” Operation
DISADVANTAGES: Narrow Wavelength Tuning Increased Laser Line Width
Compact QC Laser Spectrometer
56 m cell 0.1 s response time TE or LN2 Detectors 19 inch rack mount
MULTIPLE GASES– NH3-C2H4 (967 cm-1)
– CO2-N2O (2240 cm-1)– CH4-N2O-H2O (1270 cm-1)
NH3 at Iowa Swine Farm Automated single QC laser
instrument at 966 cm-1
Continuous operation for 4 weeks during ETV program
Enormous ammonia signals! 10 Hz data rate suitable for
eddy correlation
1.000
0.999
0.998
0.997
TRAN
SM
ISS
ION
967.40967.30FREQUENCY (cm
-1)
NH3 3 ppbpath 210 mP 50 Torr
data fit
AMMONIA IN ROOM AIR
5
4
3
2
1
0
NH
3 (p
pb)
250200150100500TIME (seconds)
55 ppt RMS noise (1 Hz)
Change from "tank" air to room air
AMMONIA DETECTION WITH QCL
Path Length 210 m Line Width 0.006 cm-1
(180 MHz)
PRECISION 55 ppt Hz-1/2
3x10-5 absorbance
U. Manchester Inst. Technol. QC-TILDAS
NH3 - NO - NO2 at Chelmsford UK Field Site August 2003
60
50
40
30
20
10
0
AM
MO
NIA
(ppb
)
8:50 AM8/10/2003
8:52 AM 8:54 AM
TIME
HAND AT INLETSILICO-STAINLESS TUBE LENGTH 10 m
ViewOpen-path FTIR in Mexico CityOpen-path FTIR in Mexico CityMichel Grutter, Edgar Flores, Roberto Basaldud Centro de Ciencias de la AtmósferaUniversidad Nacional Autónoma de México (UNAM)
Set UpOPEN PATH FTIR SPECTROMETEROPEN PATH FTIR SPECTROMETER (Grutter et al.)(Grutter et al.)
Compounds: NH3, O3, CO, NO, N2O, CO2, CH4, HCHO
sample
references
100 – 500 m
detectorspectrometer
NHNH3 3 FTIR SPECTRUM in MEXICO CITY (Grutter et al.)FTIR SPECTRUM in MEXICO CITY (Grutter et al.)
Sun Apr 06 05:25:08 2003
NH3 100 ppb
92.9 ppb
NH3
MixingRatios (ppb)
100
50
0
Mexico City NH3 FTIR Data 0
45
90
135
180
225
270
315
0 0.02 0.04 0.06 0.08 0.1
0 2 4 6 8 10 12 14 16 18 20 22 24
0.000
0.010
0.020
0.030
0.040
0.050
0.060
hrN
H3 (
ppm
)
a) b)
0 0.02 0.04 0.06 0.08 0.1N H 3 (ppm )
360
400
440
480
CO
2 (pp
m)
Fit R e su lts
Fit 1 : L in ea rEqu a tio n Y = 1 16 6 .64 5 6 2 2 * X + 36 3 .02 9 87 4 3N u m b e r o f d a ta p o in ts u se d = 7 2 8 6Ave ra ge X = 0 .02 2 1 8 0 9Ave ra ge Y = 38 8 .9 0 7R e sid ua l su m o f sq ua re s = 1 .4 4 2 4 3 E+0 0 6R e gre ssio n sum o f sq u a re s = 1 .6 5 9 75 E+0 0 6C o e f o f d e te rm in a tio n , R -sq ua re d = 0 .5 35 0 2 8R e sid ua l m ea n sq u a re , sigm a -h a t-sq 'd = 19 8 .0 2 7
DIURNAL CYCLEAPRIL 2003
CO2 CORRELATION0.9 mmol NH3/mol CO2
MEXICO CITY AIR POLLUTION STUDY, APRIL 2003
QCL (NH3)Dual TDL (NO2, HCHO)
REAR INLET
FRONT INLET
AMMONIA INLET DESIGN
650600550500450400
CO2 (ppm)
7:14 PM4/24/2003
7:16 PM 7:18 PM 7:20 PM
80
60
40
20
NH3 (ppb)
80
60
40
20
NH
3 (p
pb)
650600550500450400
CO2 (ppm)
0.12 mmol NH3 / mol CO2
General Traffic & Market AreaMexico City, 2003
Mexico City Automobile Traffic
BOSTON TUNNEL NH3
1600
1200
800
400
CO2 (ppm)
2:42 PM5/23/2003
2:44 PM 2:46 PM 2:48 PM 2:50 PM
120
80
40
NH3 (ppb)Exit Tunnel
Enter Tunnel
120
100
80
60
40
20
0
NH
3 (p
pb)
16001200800
CO2 (ppm)
0.1 mmol NH3 / mol CO2
Boston 'Big Dig' Tunnel
460
440
420
CO2 (ppm)
6:15:30 PM5/23/2003
6:16:00 PM 6:16:30 PM
20
15
10
NH3 (ppb)
20
15
10
NH
3 (p
pb)
460440420
CO2 (ppm)
0.2 mmol NH3 / mol CO2
BOSTON HIGHWAY NH3
FREEWAY OVER-PASS
QUAD-QC OPEN PATH TILDAS
Four QC Lasers with time-multiplexing
NO, NO2, N2O, NH3,CO
CO2 reference Cross-road retro-
reflector Range 200 meters
AUTOMOBILE EXHAUST PLUME SPECTRA
LASER 12240 cm-1
LASER 2967 cm-1
LASER 31906 cm-1
CO2
N2ONH3
NO
0.02 s
Automobile exhaust plume
8
6
4
2
0
CO
2, %
0.80.60.40.20.0TIME (s)
40
30
20
10
0
N2O
, ppm
60
40
20
0
NH
3, p
pm300
250
200
150
100
50
0
NO
, ppm
1994 Mitsubishi mmol/mol CO2 CO2 N2O 0.46 NH3 0.83 NO 3.4
start of plume
CATALYTIC CONVERTER WARM-UP
0
200
400
600
800
NO
, ppm
0 2 4 6 8 10 12CO2, %
cold start t = 93 s t = 133 s t = 172 s t = 208 s t = 244 s t = 280 s
0
20
40
60
80
NH
3, p
pm
0 2 4 6 8 10 12CO2, %
cold start t = 93 s t = 133 s t = 172 s t = 208 s t = 244 s t = 280 s
NO NH3
REPEATED PASSES OF SAME AUTOMOBILE0 - 5 minutes after cold start
NO emissions decrease
NH3 emissions increase
CATALYST WARM-UP
0
2
4
6
8
10N
O E
mis
sion
Rat
io (m
mol
/mol
CO
2)
6005004003002001000Time from cold start (s)
0
0.2
0.4
0.6
0.8
1.0
NH
3 an
d N
2O E
mis
sion
Rat
ios
(mm
ol/m
ol C
O2)
0
NH
3 E
mis
sion
Rat
io (m
mol
/mol
CO
2)
*
* *
*
**
*
NO N2O (expanded scale) NH3 (expanded scale)
NO N2O (N2) NH3
CONCLUSIONS
QC LASER METHOD FOR NH3 – OPEN PATH – EXTRACTIVE SAMPLING
MOBILE “MAPPING” FOR SOURCE IDENTIFICATION AND QUANTIFICATION
AUTOMOBILE EXHAUST IS SIGNIFICANT SOURCE OF URBAN AMMONIA FROM CATALYTIC REDUCTION OF NO
Acknowledgments Aerodyne Colleagues
– Joanne Shorter – Scott Herndon – David Nelson– Barry McManus– Quan Shi– Patrick Kirwin– Jeff Mulholland– Chuck Kolb
UNAM (FTIR)– Michel Grutter
M.I.T– Ed Dunlea– Luisa Molina– Mario Molina
US EPA, NSF, NASA, DOE, NISTSmall Business Innovation Research Programs
Alpes Lasers– Antoine Meuller– Yargo Bonnetti
U. Manchester Inst. Tech.– Martin Gallagher– Keith Bower– Jamie Whitehead
Danish Inst. Agriculture Sci– Willem Asman – Anton Thomsen– Kirsten Schelde