Monitoring of ambient carbon monoxide concentrations based on wavelength modulation direct absorption spectroscopy

Wang Zhen; Du Yan-Jun; Ding Yan-Jun; Li Zheng; Peng Zhi-Min

doi:10.7498/aps.71.20211772

Abstract

Wavelength modulation-direct absorption spectroscopy (WM-DAS) has the advantages of both direct absorption spectroscopy (DAS) measurable absorptivity function and wavelength modulation spectrum (WMS) with high signal-to-noise ratio (SNR). In this paper, the WM-DAS spectrum is used to measure the absorptivity of 4300.7 cm^–1 line of CO molecule and the detection limit is as low as 4 × 10^–7 (200 s) at 0.5 m optical path, room temperature and low pressure. Then, through combining the WM-DAS spectrum with a 120 m long optical path Herriott cell, at room temperature and atmospheric pressure, the standard deviation of the fitting residual error of the absorptivity function is reduced down to ~5.1 × 10^–5 (1 s). Finally, different concentrations of CO are continuously monitored by long-path WM-DAS measurement system, and compared with the results obtained from the cavity ring-down spectroscopy (CRDS). The experimental results show that the measurement results from the long-path WM-DAS and CRDS method are the same. The detection limit of CO concentration in long-path WM-DAS system is as low as 0.9 ppb (200 s), and the WM-DAS system is simple and the measurement speed is much faster than CRDS. At the same time, the long-path WM-DAS system is used to continuously monitor the atmospheric trace CO concentration and trend for one month, and the measured results are highly consistent with those from the China Environmental Monitoring Station.

Keywords:

Authors and contacts

State Key Laboratory of Power Systems, Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China

Corresponding author: Peng Zhi-Min, apspect@tsinghua.edu.cn

Funds: Project supported by the National Key R&D Program of China (Grant No. 2019YFB2006002) and the National Natural Science Foundation of China (Grant Nos. 11972213, 51906120).

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References

[1]	Zellweger C, Steinbrecher R, Laurent O, Lee H, Kim S, Emmenegger L, Steinbacher M, Buchmann B 2019 Atmos. Meas. Tech. 12 5863 Google Scholar
[2]	Chen H, Karion A, Rella C W, Winderlich J, Gerbig C, Filges A, Newberger T, Sweeney C, Tans P P 2013 Atmos. Meas. Tech. 6 1031 Google Scholar
[3]	van der Laan S, Neubert R E M, Meijer H A J 2009 Atmos. Meas. Tech. 2 549 Google Scholar
[4]	Hammer S, Griffith D W T, Konrad G, Vardag S, Caldow C, Levin I 2013 Atmos. Meas. Tech. 6 1153 Google Scholar
[5]	Adámek P, Olejníček J, Čada M, Kment Š, Hubička Z 2013 Opt. Lett. 38 2428 Google Scholar
[6]	Goldenstein C S, Spearrin R M, Jeffries J B, Hanson R K 2016 Prog. Energy Combust. 60 132
[7]	Witzel O, Klein A, Meffert C, Wagner S, Kaiser S, Schulz C, Ebert V 2013 Opt. Express 21 19951 Google Scholar
[8]	Hanson R K 2011 Proc. Combust. Inst. 33 1 Google Scholar
[9]	Pal M, Maity A, Pradhan M 2018 Laser Phys. 28 105702 Google Scholar
[10]	Maity A, Pal M, Banik1 G D, Maithani S, Pradhan M 2017 Laser Phys. Lett. 14 115701 Google Scholar
[11]	Zhou S, Liu N W, Shen C Y, Zhang L, He T B, Yu B L, Li J S 2019 Spectrochim. Acta A 2019 223 117332
[12]	Tang Y Y, Liu W Q, Kan R F, Liu J G, He Y B, Zhang Y J, Xu Z Y, Ruan J, Geng H 2011 Opt. Express 19 20224 Google Scholar
[13]	Kasyutich1 V L, Holdsworth R J, Martin P A 2008 Appl. Phys. B 92 271 Google Scholar
[14]	Stefan´ski P, Lewicki R, Sanchez N P, Tarka J, Griffin R J, Razeghi M, Tittel F K 2014 Appl. Phys. B 117 519 Google Scholar
[15]	Qiao S D, Ma Y F, He Y, Patimisco P, Sampaolo A, Spagnolo V 2021 Opt. Express 29 25100 Google Scholar
[16]	Dang J M, Yu H Y, Sun Y J, Wang Y D 2017 Infrared Phys. Technol. 82 183 Google Scholar
[17]	Li J S, Parchatka U, Fischer H 2013 Sens. Actuators, B 182 659 Google Scholar
[18]	Wei M, Ye Q H, Kan R F, Chen B, Yang C G, Xu Z Y, Chen X, Ruan J, Fan X L, Wang W, Hu M, Liu J G 2016 Chin. Phys. B 25 094210 Google Scholar
[19]	Lan L J, Ding Y J, Peng Z M, Du Y J, Liu Y F, Li Z 2014 Appl. Phys. B 117 543 Google Scholar
[20]	Silva M L, Wainner R T, Sonnenfroh D M, Rosen D I, Allen M G, Risby T H 2005 Proc. SPIE, November 17, 2005 p6010
[21]	Hangauer A, Chen J, Strzoda R, Ortsiefer M, Amann M C 2008 Opt. Lett. 33 1566 Google Scholar
[22]	Hangauer A, Chen J, Strzoda R, Fleischer M, Amann M C 2013 Opt. Express 22 13680
[23]	Ortsiefer M, Neumeyr C, Rosskopf J, Arafin S, Böhm G, Hangauer A, Chen J, Strzoda R, M.-C. Amann M C 2011 Proc. SPIE 7945 794509 Google Scholar
[24]	Ma Y F, Yu G, Zhang J B, Yu X, Sun R 2015 J. Opt. 17 055401 Google Scholar
[25]	Lou D C, Rao W, Wang K, Song J L, Jiang Y J 2020 Global Intelligent Industry Conference 2020 Proc. SPIE March 18, 2021, p117801P
[26]	陈兵, 周泽义, 康鹏, 刘安雯, 胡水明 2015 光谱学与光谱分析 35 971 Google Scholar Chen B, Zhou Z Y, Kang P, Liu A W, Hu S M 2015 Spectrosc. Spect. Anal. 35 971 Google Scholar
[27]	Peng Z M, Du Y J, Ding Y J 2020 Sensors 20 681 Google Scholar
[28]	Peng Z M, Du Y J, Ding Y J 2020 Sensors 20 616 Google Scholar
[29]	Maity A, Pal M, Banik1 G D, Maithani S, Pradhan M 2017 Laser Physics Letters 14 115701
[30]	Mazurenka M, Wada R, Shillings A J L, Butler T J A, Beames J M, Orr-Ewing A J 2005 Appl. Phys. B 81 135 Google Scholar
[31]	Li J D, Du Y J, Ding Y J, Peng Z M 2020 J. Quant. Spectrosc. Radiat. Transfer 254 107216 Google Scholar
[32]	Li J D, Du Y J, Ding Y J, Peng Z M 2021 J. Quant. Spectrosc. Radiat. Transfer 272 107790 Google Scholar
[33]	Gordon I E, Rothman L S, Hill C, et al. 2017 J. Quant. Spectrosc. Radiat. Transfer 203 3 Google Scholar
[34]	Boyer W, Lynas-Gray A E 2014 MNRAS 444 2555 Google Scholar
[35]	Allan D W 1966 Proc. IEEE 54 221 Google Scholar
[36]	Zhao G, Tan W, Jia M Y, Hou J J, Ma W G, Dong L, Zhang L, Feng X X, Wu X C, Yin W B, Xiao L T, Axner O, Jia S T 2016 Sensors 16 1544 Google Scholar
[37]	王振, 杜艳君, 丁艳军, 彭志敏 2020 物理学报 69 064204 Google Scholar Wang Z, Du Y J, Ding Y J, Peng Z M 2020 Acta Phys. Sin. 69 064204 Google Scholar
[38]	王振, 杜艳君, 丁艳军, 彭志敏 2019 物理学报 68 204204 Google Scholar Wang Z, Du Y J, Ding Y J, Peng Z M 2019 Acta Phys. Sin. 68 204204 Google Scholar
[39]	Wang Z, Du Y J, Ding Y J, Peng Z M 2020 Sensors 20 585 Google Scholar

Cited By

图 1 实验系统WM-DAS (a)与CRDS (b). ISO, 光纤隔离器; AOM, 声光调制器; APD, 雪崩光电二极管; PD, 光电二极管; DDG, 数字延迟发生器; DAQ, 数据采集卡

Figure 1. System schematic diagram of WM-DAS (a) and CRDS (b). ISO, fiber isolator; AOM, acousto-optic modulator; APD, avalanche photodiode; PD, photodiode; DDG, digital delay generator; DAQ, digital acquisition.

DownLoad: Full-Size Img PowerPoint

图 2 (a) WM-DAS波长标定; (b)测量光强I_t的傅里叶系数

Figure 2. (a) Wavelength calibration of WM-DAS; (b) Fourier coefficients of the measuring light intensity I_t.

DownLoad: Full-Size Img PowerPoint

图 3 (a)压力26 kPa、温度290 K时, WM-DAS单次测量体积分数为101 × 10^–6和53 × 10^–6的CO吸收率函数; (b) 53 × 10^–6标气和纯N₂时吸收率峰值的Allan标准差

Figure 3. (a) CO absorptivity function of 101 × 10^–6and 53 × 10^–6 measured by WM-DAS at 26 kPa and 290 K; (b) Allan standard deviation of the peak absorptivity at 53 × 10^–6 and pure N₂.

DownLoad: Full-Size Img PowerPoint

图 4 激光电流以锯齿波形式扫描时, 衰荡时间(黑色)与激光电流(蓝色)的关系

Figure 4. Relationship between the decay time (black) and the laser current (blue) when the laser current is scanned in the form of saw tooth wave.

DownLoad: Full-Size Img PowerPoint

图 5 (a) WM-DAS测量的CO(4300.7 cm^–1)吸收系数函数, 采集10³周期, 总用时1 s; (b) CRDS测量的CO(6383.09 cm^–1、线强度约为4300.7 cm^–1的0.77 %)吸收系数函数, 平均10³次, 总用时4 h

Figure 5. (a) CO (4300.7 cm^–1) absorption coefficient function measured by WM-DAS, 10³ cycles of collection, and the total time is ~1 second; (b) absorption coefficient function of CO (6383.09 cm^–1, the line strength is about 0.77% of 4300.7 cm^–1) measured by CRDS, with an average of 10³ times, with a total time of 4 hours.

DownLoad: Full-Size Img PowerPoint

图 6 WM-DAS和CRDS两种方法测量CO浓度的Allan标准差

Figure 6. Allan standard deviation of CO concentration measured by WM-DAS and CRDS.

DownLoad: Full-Size Img PowerPoint

图 7 不同浓度配比下, WM-DAS(红色)和CRDS(蓝色)连续测量结果　(a) 低浓度(1.3 × 10^–6—9.6 × 10^–6); (b) 极低浓度(0.44 × 10^–6—1.33 × 10^–6)

Figure 7. Continuous measurement results of WM-DAS (red) and CRDS (blue) under different concentration ratios: (a) Low concentration (1.3 × 10^–6–19.6 × 10^–6) (b) extremely low concentration (0.44 × 10^–6–11.33 × 10^–6).

DownLoad: Full-Size Img PowerPoint

图 8 WM-DAS和CRDS测量的不同浓度下CO的吸收系数(去除了CRDS测量的吸收系数基线以便于比较)

Figure 8. Absorption coefficient of CO measured by WM-DAS and CRDS at different concentrations (the baseline of absorption coefficient measured by CRDS is removed).

DownLoad: Full-Size Img PowerPoint

图 9 大气痕量CO连续监测原始数据(绿色)及24 h平均(蓝色), 以及监测总站测量的CO(红色)及PM2.5(黑色)

Figure 9. Atmospheric trace CO continuous monitoring raw data (green) and 24-hour average (blue), CO (red) and PM2.5 (black) measured by the monitoring station.

DownLoad: Full-Size Img PowerPoint

[1]	Zellweger C, Steinbrecher R, Laurent O, Lee H, Kim S, Emmenegger L, Steinbacher M, Buchmann B 2019 Atmos. Meas. Tech. 12 5863 Google Scholar
[2]	Chen H, Karion A, Rella C W, Winderlich J, Gerbig C, Filges A, Newberger T, Sweeney C, Tans P P 2013 Atmos. Meas. Tech. 6 1031 Google Scholar
[3]	van der Laan S, Neubert R E M, Meijer H A J 2009 Atmos. Meas. Tech. 2 549 Google Scholar
[4]	Hammer S, Griffith D W T, Konrad G, Vardag S, Caldow C, Levin I 2013 Atmos. Meas. Tech. 6 1153 Google Scholar
[5]	Adámek P, Olejníček J, Čada M, Kment Š, Hubička Z 2013 Opt. Lett. 38 2428 Google Scholar
[6]	Goldenstein C S, Spearrin R M, Jeffries J B, Hanson R K 2016 Prog. Energy Combust. 60 132
[7]	Witzel O, Klein A, Meffert C, Wagner S, Kaiser S, Schulz C, Ebert V 2013 Opt. Express 21 19951 Google Scholar
[8]	Hanson R K 2011 Proc. Combust. Inst. 33 1 Google Scholar
[9]	Pal M, Maity A, Pradhan M 2018 Laser Phys. 28 105702 Google Scholar
[10]	Maity A, Pal M, Banik1 G D, Maithani S, Pradhan M 2017 Laser Phys. Lett. 14 115701 Google Scholar
[11]	Zhou S, Liu N W, Shen C Y, Zhang L, He T B, Yu B L, Li J S 2019 Spectrochim. Acta A 2019 223 117332
[12]	Tang Y Y, Liu W Q, Kan R F, Liu J G, He Y B, Zhang Y J, Xu Z Y, Ruan J, Geng H 2011 Opt. Express 19 20224 Google Scholar
[13]	Kasyutich1 V L, Holdsworth R J, Martin P A 2008 Appl. Phys. B 92 271 Google Scholar
[14]	Stefan´ski P, Lewicki R, Sanchez N P, Tarka J, Griffin R J, Razeghi M, Tittel F K 2014 Appl. Phys. B 117 519 Google Scholar
[15]	Qiao S D, Ma Y F, He Y, Patimisco P, Sampaolo A, Spagnolo V 2021 Opt. Express 29 25100 Google Scholar
[16]	Dang J M, Yu H Y, Sun Y J, Wang Y D 2017 Infrared Phys. Technol. 82 183 Google Scholar
[17]	Li J S, Parchatka U, Fischer H 2013 Sens. Actuators, B 182 659 Google Scholar
[18]	Wei M, Ye Q H, Kan R F, Chen B, Yang C G, Xu Z Y, Chen X, Ruan J, Fan X L, Wang W, Hu M, Liu J G 2016 Chin. Phys. B 25 094210 Google Scholar
[19]	Lan L J, Ding Y J, Peng Z M, Du Y J, Liu Y F, Li Z 2014 Appl. Phys. B 117 543 Google Scholar
[20]	Silva M L, Wainner R T, Sonnenfroh D M, Rosen D I, Allen M G, Risby T H 2005 Proc. SPIE, November 17, 2005 p6010
[21]	Hangauer A, Chen J, Strzoda R, Ortsiefer M, Amann M C 2008 Opt. Lett. 33 1566 Google Scholar
[22]	Hangauer A, Chen J, Strzoda R, Fleischer M, Amann M C 2013 Opt. Express 22 13680
[23]	Ortsiefer M, Neumeyr C, Rosskopf J, Arafin S, Böhm G, Hangauer A, Chen J, Strzoda R, M.-C. Amann M C 2011 Proc. SPIE 7945 794509 Google Scholar
[24]	Ma Y F, Yu G, Zhang J B, Yu X, Sun R 2015 J. Opt. 17 055401 Google Scholar
[25]	Lou D C, Rao W, Wang K, Song J L, Jiang Y J 2020 Global Intelligent Industry Conference 2020 Proc. SPIE March 18, 2021, p117801P
[26]	陈兵, 周泽义, 康鹏, 刘安雯, 胡水明 2015 光谱学与光谱分析 35 971 Google Scholar Chen B, Zhou Z Y, Kang P, Liu A W, Hu S M 2015 Spectrosc. Spect. Anal. 35 971 Google Scholar
[27]	Peng Z M, Du Y J, Ding Y J 2020 Sensors 20 681 Google Scholar
[28]	Peng Z M, Du Y J, Ding Y J 2020 Sensors 20 616 Google Scholar
[29]	Maity A, Pal M, Banik1 G D, Maithani S, Pradhan M 2017 Laser Physics Letters 14 115701
[30]	Mazurenka M, Wada R, Shillings A J L, Butler T J A, Beames J M, Orr-Ewing A J 2005 Appl. Phys. B 81 135 Google Scholar
[31]	Li J D, Du Y J, Ding Y J, Peng Z M 2020 J. Quant. Spectrosc. Radiat. Transfer 254 107216 Google Scholar
[32]	Li J D, Du Y J, Ding Y J, Peng Z M 2021 J. Quant. Spectrosc. Radiat. Transfer 272 107790 Google Scholar
[33]	Gordon I E, Rothman L S, Hill C, et al. 2017 J. Quant. Spectrosc. Radiat. Transfer 203 3 Google Scholar
[34]	Boyer W, Lynas-Gray A E 2014 MNRAS 444 2555 Google Scholar
[35]	Allan D W 1966 Proc. IEEE 54 221 Google Scholar
[36]	Zhao G, Tan W, Jia M Y, Hou J J, Ma W G, Dong L, Zhang L, Feng X X, Wu X C, Yin W B, Xiao L T, Axner O, Jia S T 2016 Sensors 16 1544 Google Scholar
[37]	王振, 杜艳君, 丁艳军, 彭志敏 2020 物理学报 69 064204 Google Scholar Wang Z, Du Y J, Ding Y J, Peng Z M 2020 Acta Phys. Sin. 69 064204 Google Scholar
[38]	王振, 杜艳君, 丁艳军, 彭志敏 2019 物理学报 68 204204 Google Scholar Wang Z, Du Y J, Ding Y J, Peng Z M 2019 Acta Phys. Sin. 68 204204 Google Scholar
[39]	Wang Z, Du Y J, Ding Y J, Peng Z M 2020 Sensors 20 585 Google Scholar

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