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Logo optimisé par
J.-D.Bonjour, SI-DGR
13.4.93
DOAS AS AN COMPLEMENTARY TOOL FOR
LIDAR
ÉCOLE POLYTECHNIQUE
FÉDÉRALE DE LAUSANNE
MEASUREMENTS
R. Jimenez, I.Balin, H.van den Bergh and B. Calpini
20th International Laser Radar Conference
Laboratory for Air and Soil Pollution (LPAS)
Swiss Federal Institute of Technology (EPFL)
CH. 1015. LAUSANNE
[email protected]
Vichy, FRANCE
July 10-14, 2000
DOASTEI 2000 UV-VIS beam
A new DOAS TE 2000 system -Differential Optical Absorption Spectroscopy – is continuously developed at LPA-EPFL
laboratory. Measurements of O3 , NO2 and SO2 were validated during many field campaigns by comparison with many point
monitor measurements and a OPSIS DOAS system. Reference spectra studies and measurements were also performed for
BTEX, HONO, CH2O and NO3.
DOAS 2000 Optical Layout
DOAS 2000 System Method
DOAS 2000 Specificity
Based on the UV-VIS high-frequency structure of molecular
absorption spectra (differential spectra), DOAS is a
relatively new method to measure the concentration of the
trace gases in the atmosphere
Advantages:
-multi-compound measurement
-“in situ” monitoring technique
The average field concentration is retrieved by a multiple
regression of the differential field spectra fitting the sum of
the differential reference spectra.
- integrated-path measurements
-fenceline and flux measurements
DA = D C L
N
- non-contact measurements
i 1
- relatively low maintenance costs
DAfield   β i DAref, i
L ref
[Ci ] 
β i [Cio ]
L field
DOAS 2000 Technical Parameters
Coaxial Cassegrain of 8” telescope
~ 1ppb detection limit
L = 50-2000 m Optical Path
Xe Lamp 150W Light Source
33 Hz Vibrating Slit
250 to 650nm spectral range
40 nm analytical windows
PMT detection device
DA= A- Fn is the differential absorbance (A)
Fn = polynomial filter of degree n
[Ci] = concentration of the “i” compound
L = optical path
i = multiple regression coefficients
D =  - Fn is the differential UV-VIS cross section
DOAS CH2O MEASUREMENTS
DOAS BTEX MEASUREMENTS
CH2O Measurements
Region of measurements and simulation domain
DOAS on the waste water treatment plant
Vidy: Lausanne Switzerland, Sept’99
35
Oxygen Interference Problem
30
High-resolution oxygen spectrum
0.5
25
Convoluted at the DOAS 2000 spectral resolution
20
Relative Optical Density [-]
HCHO [ppb]
Solar Radiation [MJ/m2 day]
40
15
10
5
6/10
6/8
6/6
6/4
6/2
5/31
5/29
5/27
5/25
5/23
5/21
5/19
5/17
5/15
5/13
5/11
0
Date
HCHO (DOAS)
HCHO (DNPH)
Solar Radiation
0
-0.5
100%
Relative Intensity [-]
Where
Seregno-Italy, 1999
-1
75%
50%
5.7 A
25%
-1.5
0%
-10
-8
-6
-4
-2
0
2
4
6
8
10
Relative Wavelength [A]
-2
250
2D O3 and CH2O Simulation
O3 and CH2O
255
260
13th May 1998
265
270
Wavelength [nm]
275
280
Model and Measurements
Seregno on the 13th May 1998
A
B
160
O3 (DOAS 2000)
O3 (Dasibi 1008-AH)
O3 (Simulation)
140
100
80
60
0.20
10
0.15
0.10
30
5
5
0
0.05
Date, Time
20
00:00
21:00
18:00
15:00
12:00
09:00
06:00
03:00
00:00
9/11
Benzene (DOAS)
Ethylbenzene (DOAS)
Toluene (DOAS)
1,2,4-Trimethylbenzene (DOAS)
Date
A. O3 at 10:00.
Time
9/10
0
9/9
9/8
9/7
9/6
9/4
0
9/5
0.00
10
9/11
HCHO [ppb]
40
0.25
10
9/10
HCHO (DOAS 2000)
HCHO (Simulation)
15
9/9
60
0.30
9/8
BTEX [ppmC]
D
15
9/7
00:00
21:00
18:00
12:00
09:00
06:00
03:00
00:00
15:00
C
Time
50
20
0.35
9/6
NMHC
9/5
BTEX
0.40
0
9/4
20
20
25
Concentration [ppb]
0.45
40
NMHC [ppmC]
O3 [ppb]
120
DOAS BTEX measurement serie
DOAS BTEX and FID NMHC comparison
B. HCHO at 10:00.
C. O3 at 16:00.
[ppb]
POINT MONITOR and DOAS COMPARISON
[ppb]
D. HCHO at 16:00
DOAS ground measurement for LIDAR profile
CONCLUSION
O3
O3 vertical profile and O3 DOAS at the ground VifGrenoble, 26.07.99 (midnight)
O3 at 283 nm DOAS and O3 from a PM Comparison
5000
O3 (DOAS 2000) [ ppb]
160
140
4500
120
100
4000
80
60
40
3500
DOAS = 1.07 x PM + 2.0
R2 = 0.97
20
0
20
40
60
80
100
120
ASL [m]
0
Ozone Lidar
[ppb][
3000
O3 from PM [ ppb ]
NO2
2500
2000
DOAS Ozone
[ppb]
NO2 (DOAS 2000) [ppb]
NO2 at 345 nm DOAS and Point Monitor Correlation
1500
60
50
1000
40
30
This new DOASTEI 2000 system is currently used to measure the
criteria gases (NO2, O3, SO2) and take usually part in the tropospheric
air pollution measurements campaign (e.g. Milan-Italy 1998, GrenobleFrance 1999 and Lausanne –Switzerland 1999).
The new developments are on going to improve and validate the BTEX,
CH2O, NO3 and HONO measurements.
The DOAS ground measurements (e.g. O3) complete the O3 LIDAR
vertical profiles.
500
20
DOAS = 0.88 PM + 3.1
10
2
0
R = 0.78
0
0
0
10
20
30
40
NO2 (DASIBI 2108) [ppb]
50
25
50
75
60
O3 [ppb]
100
125
150
Acknowledgements: Thermo Environmental Instruments (TEI) Franklin
–USA and STEP-Vidy, Lausanne- Switzerland
http://lpas.epfl.ch/lidar/