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DOAS AS AN COMPLEMENTARY TOOL FOR LIDAR
MEASUREMENTS R. Jimenez, I.Balin, H.van den
Bergh and B. Calpini Laboratory for Air and
Soil Pollution (LPAS) Swiss Federal Institute
of Technology (EPFL) CH. 1015.
LAUSANNE bertrand.calpini_at_epfl.ch
20th International Laser Radar Conference
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.
Seregno-Italy, 1999
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 The average field concentration is
retrieved by a multiple regression of the
differential field spectra fitting the sum of the
differential reference spectra. DA ?D C
L
Advantages -multi-compound measurement -in
situ monitoring technique - integrated-path
measurements -fenceline and flux measurements -
non-contact measurements - relatively low
maintenance costs
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
Where 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, Sept99
Oxygen Interference Problem
2D O3 and CH2O Simulation 13th May 1998
O3 and CH2O Model and Measurements Seregno on
the 13th May 1998
A
B
DOAS BTEX measurement serie
DOAS BTEX and FID NMHC comparison
C
D
A. O3 at 1000. B. HCHO at 1000. C. O3 at
1600. D. HCHO at 1600
ppb
ppb
POINT MONITOR and DOAS COMPARISON
DOAS ground measurement for LIDAR profile
CONCLUSION 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, Grenoble-France 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.
O3
NO2
Acknowledgements Thermo Environmental
Instruments (TEI) Franklin USA and STEP-Vidy,
Lausanne- Switzerland
http//lpas.epfl.ch/lidar/