DETECTION OF ATMOSPHERIC GAS SPECIES BY TRACE GAS ANALYZER BASED ON - - PowerPoint PPT Presentation

DETECTION OF ATMOSPHERIC GAS SPECIES BY TRACE GAS ANALYZER BASED ON THE Xe-LAMP

S.S. SMIRNOV, P.P. GEIKO,

National Research Tomsk State University, Tomsk Institute of Monitoring of Climatic Ecological System SB RAS, Tomsk 2014

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Factors determining of light extinction

)} ) ( ) ( ) ( ( exp{ ) ( ) ( ) (

1 Ray Ray J j Mie Mie j j

C C C L I A I λ σ λ σ λ σ λ λ λ

∑

=

+ + − ⋅ ⋅ =

Fig.1 – Factors determining light extinction in the atmosphere. Passing through the open atmospheric trace, the optical radiation is absorbed by all gas components and scattered by air molecules and aerosol particles

*Platt,U., and Stutz,J. Differential Optical Absorption Spectroscopy: Principles and Applications, Springer-Verlag, BerlinHeidelberg,ISBN:978-3-540-21193-8.pp.1366–5901, (2008).

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The DOAS Principle

DOAS method is based on the representation of the spectrum of extinction

(complete cross section, fig.2) in the form of the sum smooth and differential components. Fig.2 – Principle of DOAS: Spectral dependence of the extinction cross section (left) and the absorption cross-section (right).

In DOAS technique is assumed that the spectral dependence of the light source and the apparatus do not contain any differential components, or it is completely eliminated in the process of normalization. Normalized signal of DOAS analyzer can be written as:

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( ) ( ) ( ) ( ) ( )exp ( ) ( )

• i

i i

I A B G T C L d I λ λ λ λ λ λ σ λ λ λ

+∞ −∞

⎧ ⎫ ʹ″ ʹ″ ʹ″ ʹ″ ʹ″ = − −∑ ∫ ⎨ ⎬ ⎩ ⎭

( ) exp ( ) ( ) ( )

i i R M i

B L C λ σ λ ε λ ε λ ⎧ ⎫ ʹ″ ʹ″ ʹ″ ʹ″ = − + + ∑ ⎨ ⎬ ⎩ ⎭

A( λ ) B( λ′)

• spectral transmittance of oxygen;

{ }

2 2 2

( ) exp ( )

• T

C L λ σ λ ʹ″ ʹ″ = −

1

ln ( )

m l j k k i i k j k i j

S I L C a σ λ λ

= =

= = − + ∑ ∑

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where

The DOAS Principle

– smooth spectral characteristic;. – transmission of the optical system; ¡ ¡

The system DOAS

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• Fig. 3 - The system DOAS.
• Fig. 4 – Experimental setup for DOAS spectrometer.

Source of radiation - UV radiation the xenon lamp of high pressure. Coaxial telescope - optical scheme of the telescope - transmitting and receiving channels. Retroreflector (angel reflector) – reflects radiation falling on it and is fastened on any support on the remote end of air path. Monochromator-Spectrograph is intended for decomposition of radiation in spectrum. Diode array with the electronic unit is used for detection of optical radiation across a broad spectral range.

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Conditions of the sensing

Fig.5 – Space photo of atmospheric trace. Measurements were carried out in Tomsk. The atmospheric trace passed in area of sq.Yuzhnaya. Figure 5 illustrates a snapshot of atmospheric trace by satellite. The optical path length of 484m. Sensing of was conducted from February to May.

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General characteristic of measurement results

Tab.1. Average daytime concentrations of some gases (ppb).

Month

Formaldehyde (CH2O) Nitrogen dioxide (NO2) Ozone (O3) Benzene (C6H6) Toluene (C7H8) Phenol (C6H6O) Benzaldehyde (C7H60) Sulfur dioxide (SO2)

February 9,98 13,04 20,4 4,59 12,2 0,382 0,356 0,777 March 8,41 28,3 18,35 6,74 10,6 0,776 1,71 0,574 April 7,64 22,33 27,9 6,16 8,11 0,727 0,765 0,244 May 2,94 7,5 35,8 1,89 7,5 0,961 2,41 0,19 Over the entire period 7,24 17,79 25,61 4,84 9,6 0,71 1,31 0,446

• av. d. MPС

2,5 20,94 15 31,34 160 0,789 9,06 18

The measurements were performed on average ultraviolet (202 – 335 nm), that

allowed to carry out parallel synchronous measurements for a number of trace gases in the atmosphere, such as ozone, nitrogen oxides, formaldehyde, sulfur dioxide, phenol, etc..

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General characteristic of measurement results

Rhumb Formaldehyde (CH2O) Nitrogen dioxide (NO2) Ozone (O3) Benzene (C6H6) Toluene (C7H8) Phenol (C6H6O) Benzaldehyde (C7H60) N

• NE

10,5 7,33 22,94 2,39 12,16 0,29 1,2 E 12,2 4 16 4,95 0,66 SE 15,1 1,18 3,16 S 5,82 14,84 17,2 1,3 8,16 0,48 2,31 SW 4,49 13,08 21,3 4,31 8,36 0,74 2,15 W 5,31 16,14 37,9 6,95 13,05 0,59 2,59 NW 1,56 10,8 41,5 7,36 4,56 0,59 1,57

From data of table 2 follows that for ozone increase of average concentration corresponds to

the directions the West and the northwest. For formaldehyde – the northeast and the East. Tab.2. Average daytime concentration of gases (ppb) concerning the wind direction. (Note. In line, N points, crossed out sections as during supervision the wind of this direction was absent are put.)

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General characteristic of measurement results

Fig.6 – Average daytime values of concentration of ozone, nitrogen dioxide and formaldehyde concerning the wind directions.

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Comparison of results of sensing

The top graph (left) result of measurements from the range "Background" near Kireevsk (60 km to the west of Tomsk, 56°25'N, 84°04'E). The bottom graph results of measurements from the basic experimental complex (BEC) near Tomsk (56 °29‘ N, 85 °04‘E ). On the right side graph of results of measurements of DOAS.

*V.E. ZUEV Institute of atmospheric optics SB RAS, [electronic resource]: http://iao.ru/ru/online, updating date 2.06.2014.

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Comparison of results of sensing

For concentrations of nitrogen dioxide obtained by DOAS is observed similarity to the data range, "Background". Comparing the received concentration given for a city zone, by means of DOAS, approximately twice less.

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Comparison of results of sensing

Sulfur dioxide concentrations obtained DOAS-ohm, two times less than at the station BEC and ten times less than the landfill Background.

Daily variation of concentrations

• Fig. 10 – Daily variations of concentrations ozone.

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Daily variation of concentrations

• Fig. 11 – Daily variation of concentrations nitrogen dioxide.

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Daily variation of concentrations

• Fig. 12 – Daily variation of concentrations formaldehyde.

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Daily variation of concentrations

• Fig. 13 – Daily variation of concentrations ozone and nitrogen dioxide .

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Summary

• Some results of synchronous measurements of gas pollution concentration by

means of a trace gas analyzer of DOAS in Tomsk are represented.

• Measurement results were compared with data obtained at the site "Background"

and the station BEC. Analysis showed that the resulting concentration DOAS th for three gases (O3, NO2, SO2) two times less than the plant BECs. For landfill Background: ozone and nitrogen dioxide observed similarity of the results

• btained, and the value of sulfur dioxide concentrations about 10 times less.
• It is revealed that during measurements of ozone concentration and formaldehyde

concentration near Lytkin St. of Tomsk exceeded several times the village of maximum concentration limit.

• It is shown that, the gas analyzer on the basis of the DOAS method is effective

system for the prevention of dangerous levels of pollution of the atmosphere.

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Thanks for attention

Smirnov Sergey SSSmirnov@sibmail.com