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NO3自由基是夜间大气化学中最重要的氧化剂, 控制着多种痕量气体成分的氧化及去除, 了解NO3自由基的化学过程对研究灰霾等大气污染过程意义重大. NO3自由基浓度低、活性强, 实现大气NO3自由基的高灵敏度准确测量相对困难. 本文介绍了大气NO3自由基的宽带腔增强吸收光谱定量方法, 采用红光LED作为宽带腔增强吸收光谱系统光源, 设计低损耗且适合国内高颗粒物环境的采样气路, 并通过LED光源测试确定最佳工作电流和温度; 通过采用白天的大气谱作为背景光谱参与NO3自由基的光谱拟合过程,减少水汽对NO3自由基光谱反演的干扰;通过对镜片反射率和有效腔长进行标定, 对系统性能进行Allan方差分析, 该宽带腔增强吸收光谱系统在光谱采集时间为10 s的情况下, NO3自由基极限探测灵敏度为0.75 pptv, 总测量误差约为16%. 在合肥开展了实际大气NO3自由基观测, 观测期间NO3自由基的浓度范围从低于探测限到23.4 pptv, NO3自由基浓度呈现夜间高、白天低的特征, 符合NO3 变化规律, 表明该宽带腔增强吸收光谱系统能够用于实际大气NO3自由基的高灵敏度测量.
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关键词:
- NO3 /
- 宽带腔增强吸收光谱技术 /
- 高灵敏度
NO3 radical is the most important oxidant in atmospheric chemistry at night, and it controls the oxidation and removal of various trace gas components in the atmosphere. The understanding of the chemical process of NO3 radical is of great significance for studying the atmospheric pollution processes such as haze. The NO3 radical has a low concentration and strong activity, so it is relatively difficult to measure accurately. We report here in this paper an instrument for unambiguously measuring NO3 based on broadband cavity enhanced absorption spectroscopy (BBCEAS). To achieve the robust performance and system stability under diverse conditions, this BBCEAS instrument has been developed, with efficient sampling, and resistance against vibration and temperature change improved, and the BBCEAS instrument also has low-power consumption. The 660-nm-wavelemngth light-emitting diode (LED) is used as a light source of the BBCEAS system. The sampling gas path with low loss and suitable for domestic high-particle environment is designed. Through the LED light source test, the optimal working current and temperature can be obtained to achieve the acquisition of NO3 absorption spectrum with high signal-to-noise ratio. Considering the fact that the water vapor absorption is an important interference factor for the measurement of NO3 radical by BBCEAS, the daytime atmospheric measurement spectrum is used as a background spectrum, and participates in spectral fitting of NO3 to reduce the effect of water vapor. The mirror reflectivity and effective cavity length are calibrated, and the Allan variance analysis is also carried out. The reflectance of the mirror can reach about 0.99993 at 662 nm (NO3 absorption peak), and the corresponding theoretical effective optical path can reach more than 7 km, which can meet the measurement requirements of atmospheric NO3 radicals. The detection limit (1σ) of 0.75 pptv for NO3 is achieved with an acquisition time of 10 s and a total measurement error of about 16%. The atmospheric NO3 radical observation is carried out in Hefei. During the observation period, the highest NO3 concentration is 23.4 pptv, demonstrating the promising potential applications in in-situ, sensitive, accurate and fast simultaneous measurements of NO3 in the future by using the developed broadband cavity enhanced absorption spectroscopy.-
Keywords:
- NO3 /
- BBCEAS /
- high sensitivity
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[3] Platt U, Alicke B, Dubois R, Geyer A, Hofzumahaus A, Holland F, Martinez M, Mihelcic D, Klupfel T, Lohrmann B, Patz W, Perner D, Rohrer F, Schafer J, Stutz J 2002 J. Atmos. Chem. 42 359Google Scholar
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[5] Platt U, Perner D, Winer A M, Harris G W, Pitts J N 1980 Geophys. Res. Lett. 7 89Google Scholar
[6] Wood E C, Wooldridge P J, Freese J H, Albrecht T, Cohen R C 2003 Environ. Sci. Technol. 37 5732Google Scholar
[7] Slusher D L, Huey L G, Tanner D J, Flocke F M, Roberts J M 2004 J. Geophys. Res. Atmos. 109 D19315Google Scholar
[8] Mihelcic D, Volzthomas A, Patz H W, Kley D 1990 J. Atmos. Chem. 11 271Google Scholar
[9] Wang D, Hu R, Xie P, Liu J, Liu W, Qin M, Ling L, Zeng Y, Chen H, Xing X, Zhu G, Wu J, Duan J, Lu X, Shen L 2015 J. Quant. Spectrosc. Radiat. Transfer 166 25
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[28] Meinen J, Thieser J, Platt U, Leisner T 2010 Atmos. Chem. Phys. 10 3901Google Scholar
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[30] Fiedler S E, Hese A, Ruth A A 2003 Chem. Phys. Lett. 371 284Google Scholar
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[32] Washenfelder R A, Langford A O, Fuchs H, Brown S S 2008 Atmos. Chem. Phys. 8 7779Google Scholar
[33] Shardanand, Rao A D P 1977 NASA Technical Note
[34] Kern C, Trick S, Rippel B, Platt U 2006 Appl. Opt. 45 2077Google Scholar
[35] Yokelson R J, Burkholder J B, Fox R W, Talukdar R K, Ravishankara A R 1994 J. Phys. Chem. 98 13144Google Scholar
[36] Voigt S, Orphal J, Burrows J P 2002 J. Photochem. Photobiol., A 149 1Google Scholar
[37] Rothman L S, Jacquemart D, Barbe A, Benner D C, Birk M, Brown L R, Carleer M R, Chackerian C, Chance K, Coudert L H 2005 J. Quant. Spectrosc. Radiat. Transfer 96 139Google Scholar
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图 5 实测大气中NO3的光谱反演实例 (a) 灰线是实测大气的吸收谱, 红线是拟合谱; (b) 灰线是NO3的吸收谱, 红线是拟合谱, 反演浓度12.2 ± 0.61 pptv; (c) 灰线是NO2的相对吸收谱, 红线是拟合谱; (d) 灰线是水汽的相对吸收谱, 红线是拟合谱; (e) 拟合残差谱, 标准偏差为8.7 × 10–10
Fig. 5. Spectral inversion example of NO3: (a) The grey line is the absorption spectrum of the measured atmosphere, and the red line is the fitting spectrum; (b) the gray line is the absorption spectrum of NO3 and the red line is the fitting spectrum, concentration of NO3 is 12.2 ± 0.61 pptv; (c) the grey line is the relative absorption spectrum of NO2, and the red line is the fitting spectrum; (d) the gray line is the relative absorption spectrum of water vapor, and the red line is the fitting spectrum; (e) the gray line is residual spectrum, and the standard deviation of residual spectrum is 8.7 × 10–10.
图 6 检测限分析 (a) NO3的Allan方差和标准方差随平均时间的变化曲线; (b) 4 s积分时间情况下的NO3浓度统计图; (c) 4 s积分时间情况下的NO3浓度时间序列
Fig. 6. Analysis of detection limit: (a) Change curves of Allan variance and standard variance of NO3 with average time; (b) statistical chart of NO3 concentration with 4 s integration time; (c) time series of NO3 concentration with 4 s integration time.
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[1] Levy H 1971 Science 173 141Google Scholar
[2] Wayne R P, Barnes I, Biggs P, Burrows J P, Canosamas C E, Hjorth J, Lebras G, Moortgat G K, Perner D, Poulet G, Restelli G, Sidebottom H 1991 Atmos. Environ. Part A 25 1
[3] Platt U, Alicke B, Dubois R, Geyer A, Hofzumahaus A, Holland F, Martinez M, Mihelcic D, Klupfel T, Lohrmann B, Patz W, Perner D, Rohrer F, Schafer J, Stutz J 2002 J. Atmos. Chem. 42 359Google Scholar
[4] Stutz J, Alicke B, Ackermann R, Geyer A, White A, Williams E 2004 J. Geophys. Res. Atmos. 109 D12306Google Scholar
[5] Platt U, Perner D, Winer A M, Harris G W, Pitts J N 1980 Geophys. Res. Lett. 7 89Google Scholar
[6] Wood E C, Wooldridge P J, Freese J H, Albrecht T, Cohen R C 2003 Environ. Sci. Technol. 37 5732Google Scholar
[7] Slusher D L, Huey L G, Tanner D J, Flocke F M, Roberts J M 2004 J. Geophys. Res. Atmos. 109 D19315Google Scholar
[8] Mihelcic D, Volzthomas A, Patz H W, Kley D 1990 J. Atmos. Chem. 11 271Google Scholar
[9] Wang D, Hu R, Xie P, Liu J, Liu W, Qin M, Ling L, Zeng Y, Chen H, Xing X, Zhu G, Wu J, Duan J, Lu X, Shen L 2015 J. Quant. Spectrosc. Radiat. Transfer 166 25
[10] Wang H, Chen J, Lu K 2017 Atmos. Meas. Tech. 10 1465Google Scholar
[11] Wagner N L, Dube W P, Washenfelder R A, Young C J, Pollack I B, Ryerson T B, Brown S S 2011 Atmos. Meas. Tech. 4 1227Google Scholar
[12] Li Z, Hu R, Xie P, Wang H, Lu K, Wang D 2018 Sci. Total Environ. 613 131
[13] Li Z, Hu R, Xie P, Hao C, Liu W 2018 Opt. Express 26 A433Google Scholar
[14] Ling L, Xie P, Qin M, Fang W, Jiang Y, Hu R, Zheng N 2013 Chin. Opt. Lett. 11 063001Google Scholar
[15] Ball S M, Langridge J M, Jones R L 2004 Chem. Phys. Lett. 398 68Google Scholar
[16] Langridge J M, Ball S M, Jones R L 2006 Analyst 131 916Google Scholar
[17] Kennedy O J, Ouyang B, Langridge J M, Daniels M J S, Bauguitte S, Freshwater R, McLeod M W, Ironmonger C, Sendall J, Norris O, Nightingale R, Ball S M, Jones R L 2011 Atmos. Meas. Tech. 4 1759Google Scholar
[18] Vaughan S, Gherman T, Ruth A A, Orphal J 2008 Phys. Chem. Chem. Phys. 10 4471Google Scholar
[19] Wu T, Chen W, Fertein E, Cazier F, Dewaele D, Gao X 2011 Appl. Phys. B 106 501
[20] Gherman T, Venables D S, Vaughan S, Orphal J, Ruth A A 2007 Environ. Sci. Technol. 42 890
[21] Min K E, Washenfelder R A, Dubé W P, Langford A O, Edwards P M, Zarzana K J, Stutz J, Lu K, Rohrer F, Zhang Y, Brown S S 2016 Atmos. Meas. Tech. 9 423Google Scholar
[22] Duan J, Qin M, Ouyang B, Fang W, Li X, Lu K, Tang K, Liang S, Meng F, Hu Z, Xie P, Liu W, Häsler R 2018 Atmos. Meas. Tech. 11 4531Google Scholar
[23] Thalman R, Volkamer R 2010 Atmos. Meas. Tech. 3 1797Google Scholar
[24] Liang S, Qin M, Xie P, Duan J, Fang W, He Y, Xu J, Liu J, Li X, Tang K, Meng F, Ye K, Liu J, Liu W 2019 Atmos. Meas. Tech. 12 2499Google Scholar
[25] Hoch D J, Buxmann J, Sihler H, Pöhler D, Zetzsch C, Platt U 2014 Atmos. Meas. Tech. 7 199Google Scholar
[26] Dorn H P, Apodaca R L, Ball S M, Brauers T, Brown S S, Crowley J N, Dubé W P, Fuchs H, Häseler R, Heitmann U, Jones R L, Kiendler-Scharr A, Labazan I, Langridge J M, Meinen J, Mentel T F, Platt U, Pöhler D, Rohrer F, Ruth A A, Schlosser E, Schuster G, Shillings A J L, Simpson W R, Thieser J, Tillmann R, Varma R, Venables D S, Wahner A 2013 Atmos. Meas. Tech. 6 1111Google Scholar
[27] Venables D S, Gherman T, Orphal J, Wenger J C, Ruth A A 2006 Environ. Sci. Technol. 40 6758Google Scholar
[28] Meinen J, Thieser J, Platt U, Leisner T 2010 Atmos. Chem. Phys. 10 3901Google Scholar
[29] Wu T, Coeur-Tourneur C, Dhont G, Cassez A, Fertein E, He X, Chen W 2014 J. Quant. Spectrosc. Radiat. Transfer 133 199Google Scholar
[30] Fiedler S E, Hese A, Ruth A A 2003 Chem. Phys. Lett. 371 284Google Scholar
[31] Lu X, Qin M, Xie P H, Duan J, Fang W, Ling L Y, Shen L L, Liu J G, Liu W Q 2016 Chin. Phys. B 25 024210Google Scholar
[32] Washenfelder R A, Langford A O, Fuchs H, Brown S S 2008 Atmos. Chem. Phys. 8 7779Google Scholar
[33] Shardanand, Rao A D P 1977 NASA Technical Note
[34] Kern C, Trick S, Rippel B, Platt U 2006 Appl. Opt. 45 2077Google Scholar
[35] Yokelson R J, Burkholder J B, Fox R W, Talukdar R K, Ravishankara A R 1994 J. Phys. Chem. 98 13144Google Scholar
[36] Voigt S, Orphal J, Burrows J P 2002 J. Photochem. Photobiol., A 149 1Google Scholar
[37] Rothman L S, Jacquemart D, Barbe A, Benner D C, Birk M, Brown L R, Carleer M R, Chackerian C, Chance K, Coudert L H 2005 J. Quant. Spectrosc. Radiat. Transfer 96 139Google Scholar
[38] Qin M, Xie P, Su H, Gu J, Peng F, Li S, Zeng L, Liu J, Liu W, Zhang Y 2009 Atmos. Environ. 43 5731Google Scholar
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