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Development of optical isotope techniques has provided scientists with a set of powerful tools for investigating the sources and sink of atmospheric CO2. Here we describe a continuous, high precision, compact and portable carbon dioxide isotope ratio laser multi-pass cell spectrometer with a tunable distribute feedback laser at 2.008 μm based on tunable diode laser absorption spectroscopy and, the spectrometer has good temperature and pressure stability. In order to deduce the noise, drift effect and background changes associated with low level signals, a superior signal processing technique of wavelet denoising, which possesses multi-level analytical resolutions both in time and frequency-domains, is introduced. After evaluating the method, evaluation ability and applicabilities of several common wavelet functions are analyzed and tested, the wavelet function of Haar is selected as an optimal wavelet basis function. Based on the analysis of the optimal decomposition level of Haa wavelet function, the VISU function is selected as an optimal wavelet threshold function. The denoising effect and measurement precision are evaluated by use of the VISU threshold function in the measurement process of carbon dioxide stable isotope ratio. The measurement results of carbon dioxide stable isotope ratio before and after suppressing the noises are compared in the same experiment conditions and, the inconsistent reasons of the measured results are theoretically analyzed. This technique allows the measurement of the δ-value for carbon dioxide isotopic ratios with a precision of -12.5‰ and and the measuremnt results show that the wavelet denoising measuring results have higher measurement accuracy, and the measurement precise of carbon dioxide isotope ratio is 7.3 times the original measurement results. The application of the wavelet denoising to the carbon dioxide isotope ratio measurement for the first time proves that the capability of the new near-infrared direct absorption technique to measure isotope ratio can permit high-frequency, near-continuous isotope measurement and obtain the high precision and accurate real-time stable isotope data directly in the field. This technique provides an important tool for studying the resource and sink of green house gases in the future.
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Keywords:
- isotope measurement /
- novel multi-pass cell /
- wavelet denoising /
- measurement precise
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[13] Li X X, Xu L, Gao M G, Tong J J, Jin L, Li S, Wei X L, Feng M C 2013 Acta Phys. Sin. 62 180203 (in Chinese)[李相贤, 徐亮, 高闽光, 童晶晶, 金岭, 李胜, 魏秀丽, 冯明春2013物理学报62 180203]
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[22] Wu T, Chen W D, Kerstel E, Fertein E, Gao X M, Koeth J, Rößner K, Brckner D 2010 Opt. Lett. 35 0146
[23] Yang Q 2011 International Conference on Electronics & Optoelectronics 3 129
[24] Luisier F, Vonesch C, Blu T, Unser M 2009 IEEE International Symposium on Biomedical Imaging 29 310
[25] Ma Y, Wang X Y, Yong H 2011 CAC 28 303 (in Chinese)[马毅, 汪西原, 雍慧2011计算机与应用化学28 303]
[26] Kumar H S, Pai P S, Sriram N S, Vijay G S 2013 Procedia Engineering 64 805
[27] Gradolewski D, Redlarski G 2014 Comput. Biol. Med. 52 119
[28] Naga R A, Chandralingam S, Anjaneyulu T, Satyanarayana K 2012 Meas. Sci. Rev. 12 46
[29] Xu J, Kawashima S 2015 Arch. Ration. Mech. Anal. 28 1
[30] Joseph F B, Todd B S, Max L 1992 Appl. Opt. 3 1921
[31] Werle P 2011 Appl. Phys. B 102 313
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[1] Liu L X, Zhou L X, Vaughn B, Miller J B, Brand W A, Rothe M, Xia L J 2014 J. Geophys. Res. Atmos. 119 5602
[2] Mai B R, Deng X J, An X Q, Liu X T, Li F, Liu X 2014 China Environmental Science 34 1098 (in Chinese)[麦博儒, 邓雪娇, 安兴琴, 刘显通, 李菲, 刘霞2014中国环境科学34 1098]
[3] Trend W 2016 Nature 531 281
[4] Quéré C L, Andres R J, Boden T, et al. 2013 Earth Syst. Sci. Data 5 165
[5] Marland G 2012 Nat. Clim. Change 2 645
[6] Sturm P, Tuzson B, Henne S, Emmenegger L 2013 Atmos. Meas. Tech. 6 1659
[7] Brass M, Röckmann T 2010 Atmos. Meas. Tech. 3 1707
[8] Zare R N, Kuramoto D S, Haase C, Tan S M, Crosson E R, Saad Nabil M R 2009 PNAS 106 10928
[9] McManus J B, Nelson D D, Zahniser M S 2015 Opt. Express 23 6569
[10] Sayres D S, Moyer E J, Hanisco T F, et al. 2009 Rev. Sci. Instrum. 80 044102
[11] Wang C, Srivastava N, Jones B A, Rreese R B 2008 Appl. Phys. B 92 259
[12] Joseph F B, Todd B S, Max L 1992 Appl. Opt. 31 1921
[13] Li X X, Xu L, Gao M G, Tong J J, Jin L, Li S, Wei X L, Feng M C 2013 Acta Phys. Sin. 62 180203 (in Chinese)[李相贤, 徐亮, 高闽光, 童晶晶, 金岭, 李胜, 魏秀丽, 冯明春2013物理学报62 180203]
[14] Pang J P, Wen X F, Sun X M 2016 Sci. Total. Environ. 539 322
[15] Bartlome R, Sigrist M W 2009 Opt. Lett. 34 866
[16] Li J S, Yu B L, Fischer H 2015 Appl. Spectrosc. 69 496
[17] Zheng C T, Ye W L, Huang J Q, Cao T S, Lv M, Dang J M, Wang Y D 2014 Sens. Actuators B 190 249
[18] Bergamaschi P, Schupp M, Harris G W 1994 Appl. Opt. 33 7704
[19] Zhang T W, Krooss B M 2001 Geochim. Cosmochim. Acta 65 2723
[20] Kerstel E R, Trigt R V, Dam N, Reuss J, Meijer H A J 1999 Anal. Chem. 71 5297
[21] Wang Y, Mo J Y 2005 Spectrosc. Spect. Anal. 25 124 (in Chinese)[王瑛, 莫金垣2005光谱学与光谱分析25 124]
[22] Wu T, Chen W D, Kerstel E, Fertein E, Gao X M, Koeth J, Rößner K, Brckner D 2010 Opt. Lett. 35 0146
[23] Yang Q 2011 International Conference on Electronics & Optoelectronics 3 129
[24] Luisier F, Vonesch C, Blu T, Unser M 2009 IEEE International Symposium on Biomedical Imaging 29 310
[25] Ma Y, Wang X Y, Yong H 2011 CAC 28 303 (in Chinese)[马毅, 汪西原, 雍慧2011计算机与应用化学28 303]
[26] Kumar H S, Pai P S, Sriram N S, Vijay G S 2013 Procedia Engineering 64 805
[27] Gradolewski D, Redlarski G 2014 Comput. Biol. Med. 52 119
[28] Naga R A, Chandralingam S, Anjaneyulu T, Satyanarayana K 2012 Meas. Sci. Rev. 12 46
[29] Xu J, Kawashima S 2015 Arch. Ration. Mech. Anal. 28 1
[30] Joseph F B, Todd B S, Max L 1992 Appl. Opt. 3 1921
[31] Werle P 2011 Appl. Phys. B 102 313
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