Development of an incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) instrument for autonomous field measurements of HONO and NO2 in a rural area

2021 ◽  
Author(s):  
Lingshuo Meng ◽  
Gaoxuan Wang ◽  
Cécile Coeur ◽  
Alexandre Tomas ◽  
Tao Wu ◽  
...  
Keyword(s):  
Rural Area ◽  
Absorption Spectroscopy ◽  
Atmospheric Chemistry ◽  
Nitrous Acid ◽  
Trace Gases ◽  
Ambient Air ◽  
Rural Site ◽  
Oh Radicals ◽  
Enhanced Absorption ◽  
Cavity Enhanced Absorption Spectroscopy

<p>Nitrous acid (HONO) is one of the important atmospheric trace gases due to its contribution to the cycles of nitrogen oxides (NOx) and hydrogen oxides (HOx). In particular it acts as a precursor of tropospheric OH radicals, which is responsible for the self-cleansing capacity of the atmosphere [1,2]. We developed an instrument based on incoherent broadband cavity enhanced absorption spectroscopy (IBBCEAS) for automatic measurement of HONO in a rural area in a summer period during a field "Campagne d’OBservation Intensive des Aérosols et précurseurs à Caillouël-Crépigny (COBIACC)" in France. IBBCEAS technique is now extensively used in field applications for the measurements of both trace gases and aerosols [3,4].</p><p>Real-time in situ measurements of HONO and NO<sub>2</sub> have been simultaneously carried out. The IBBCEAS instrument performance has been demonstrated and validated through lab-based tests, and in particular through field intercomparison via side-by-side measurements of temporal concentration profiles of HONO and NO<sub>2</sub> in the rural area. The intercomparison of the concentration measurements between IBBCEAS and an instrument called MARGA (Monitor for AeRosols and Gases in Ambient air) for HONO, and IBBCEAS vs. a reference NOx analyzer for NO<sub>2</sub>. Good agreements have been observed which demonstrated the performance of the developed IBBCEAS instrument for the measurement of atmospheric HONO concentration (<5 ppb) in a rural area.</p><p>The preliminary experimental results will be presented and discussed.</p><p><strong>Acknowledgments</strong> This work was supported by the CPER CLIMIBIO program and the Labex CaPPA project (ANR-10-LABX005). The authors highly appreciate the offers of Mr. Eric Wetzels from Polyfluor Plastics bv for the help in our instrumental conception involving Teflon pipe.</p><p><strong>References</strong></p><p>[1] X. Li, T. Brauers, R. Häseler, R. Bohn, H. Fuchs, A. Hofzumahaus, F. Holland, S. Lou, et al., Exploring the atmospheric chemistry of nitrous acid (HONO) at a rural site in Southern China, Atmos. Chem. Phys. <strong>12</strong> (2012) 1497-1513.</p><p>[2] H. Su, Y. Cheng, M. Shao, D. Gao, Z. Yu, L. Zeng, J. Slanina, et al., Nitrous acid (HONO) and its daytime sources at a rural site during the 2004 PRIDE‐PRD experiment in China, J. Geophys. Res. <strong>113</strong> (2008) D14312.</p><p>[3] T. Wu, Q. Zha, W. Chen, Z. Xu, T. Wang, X. He, Development and deployment of a cavity enhanced UV-LED spectrometer for measurements of atmospheric HONO and NO<sub>2</sub> in Hong Kong, Atmos. Environ. <strong>95</strong> (2014) 544-551.</p><p>[4] L. Meng, G. Wang, P. Augustin, M. Fourmentin, Q. Gou, E. Fertein, T. N. Ba, C. Coeur, A. Tomas, W. Chen, Incoherent broadband cavity enhanced absorption spectroscopy-based strategy for direct measurement of aerosol extinction in lidar blind zone, Opt. Lett. <strong>45 </strong>(2020) 1611-1614.</p>

scholarly journals Broadband cavity-enhanced absorption spectroscopy in the ultraviolet spectral region for measurements of nitrogen dioxide and formaldehyde

2016 ◽  
Vol 9 (1) ◽  
pp. 41-52 ◽  
Author(s):  
R. A. Washenfelder ◽  
A. R. Attwood ◽  
J. M. Flores ◽  
K. J. Zarzana ◽  
Y. Rudich ◽  
...  
Keyword(s):  
Nitrogen Dioxide ◽  
Absorption Spectroscopy ◽  
Spectral Region ◽  
Trace Gases ◽  
Ambient Air ◽  
Array Detector ◽  
Enhanced Absorption ◽  
Cavity Enhanced Absorption Spectroscopy ◽  
Ultraviolet Spectral Region ◽  
Standard Additions

Abstract. Formaldehyde (CH2O) is the most abundant aldehyde in the atmosphere, and it strongly affects photochemistry through its photolysis. We describe simultaneous measurements of CH2O and nitrogen dioxide (NO2) using broadband cavity-enhanced absorption spectroscopy in the ultraviolet spectral region. The light source consists of a continuous-wave diode laser focused into a Xenon bulb to produce a plasma that emits high-intensity, broadband light. The plasma discharge is optically filtered and coupled into a 1 m optical cavity. The reflectivity of the cavity mirrors is 0.99930 ± 0.00003 (1− reflectivity  =  700 ppm loss) at 338 nm, as determined from the known Rayleigh scattering of He and zero air. This mirror reflectivity corresponds to an effective path length of 1.43 km within the 1 m cell. We measure the cavity output over the 315–350 nm spectral region using a grating monochromator and charge-coupled device array detector. We use published reference spectra with spectral fitting software to simultaneously retrieve CH2O and NO2 concentrations. Independent measurements of NO2 standard additions by broadband cavity-enhanced absorption spectroscopy and cavity ring-down spectroscopy agree within 2 % (slope for linear fit  = 1.02 ± 0.03 with r2 = 0.998). Standard additions of CH2O measured by broadband cavity-enhanced absorption spectroscopy and calculated based on flow dilution are also well correlated, with r2 = 0.9998. During constant mixed additions of NO2 and CH2O, the 30 s measurement precisions (1σ) of the current configuration were 140 and 210 pptv, respectively. The current 1 min detection limit for extinction measurements at 315–350 nm provides sufficient sensitivity for measurement of trace gases in laboratory experiments and ground-based field experiments. Additionally, the instrument provides highly accurate, spectroscopically based trace gas detection that may complement higher precision techniques based on non-absolute detection methods. In addition to trace gases, this approach will be appropriate for measurements of aerosol extinction in ambient air, and this spectral region is important for characterizing the strong ultraviolet absorption by brown carbon aerosol.

scholarly journals Comparison of nitrous acid detection using open-path incoherent broadband cavity-enhanced absorption spectroscopy and extractive long-path absorption photometry

2021 ◽  
Author(s):  
Sophie Dixneuf ◽  
Albert A. Ruth ◽  
Rolf Häseler ◽  
Theo Brauers ◽  
Franz Rohrer ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
Nitrous Acid ◽  
Hot Spot ◽  
Integration Time ◽  
Mixing Ratios ◽  
Enhanced Absorption ◽  
Cavity Enhanced Absorption Spectroscopy ◽  
Open Path ◽  
Ccd Detector ◽  
No2 Detection

Abstract. An instrument based on 20 m open-path incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) was established at the Jülich SAPHIR chamber in Spring 2011. The setup was optimized for the detection of HONO and NO2 in the near UV region 352–386 nm, utilizing a bright hot-spot Xe-arc lamp and a UV-enhanced CCD detector. A 2σ detection limit of 26 pptv for HONO and 76 pptv for NO2 was achieved for an integration time of 1 min. Methacrolein has also been detected at mixing ratios below 5 ppbv. The IBBCEAS instrument’s performance for HONO and NO2 detection was compared to that of extractive wet techniques, long-path absorption photometry (LOPAP) and chemiluminescence spectrometry (CLS) NOx detection, respectively.

Sensitive Detection of Ambient Formaldehyde by Incoherent Broadband Cavity Enhanced Absorption Spectroscopy

2020 ◽  
Author(s):  
Jingwei Liu ◽  
Xin Li ◽  
Yiming Yang ◽  
Haichao Wang ◽  
Cailing Kuang ◽  
...  
Keyword(s):  
Light Intensity ◽  
Light Source ◽  
Absorption Spectroscopy ◽  
Fiber Bundle ◽  
Ambient Air ◽  
Optical Path ◽  
Enhanced Absorption ◽  
Cavity Enhanced Absorption Spectroscopy ◽  
Near Ultraviolet ◽  
Type Fiber

<p>Formaldehyde (HCHO) is the most abundant atmospheric carbonyl compound and plays an important role in the troposphere. However, HCHO detection via traditional incoherent broadband cavity enhanced absorption spectroscopy (IBBCEAS) is limited by short optical path lengths and weak light intensity. Thus, a new light-emitting diode (LED)-based IBBCEAS was developed herein to measure HCHO in ambient air. Two LEDs (325 and 340 nm) coupled by a Y-type fiber bundle were used as an IBBCEAS light source, which provided both high light intensity and a wide spectral fitting range. The reflectivity of the two cavity mirrors used herein was 0.99965 (1 – reflectivity = 350 ppm loss) at 350 nm, which corresponded with an effective optical path length of 2.15 km within a 0.84 m cavity. At an integration time of 30 s, the measurement precision (1σ) for HCHO was 380 parts per trillion volume (pptv) and the corresponding uncertainty was 8.3%. The instrument was successfully deployed for the first time in a field campaign and delivered results that correlated well with those of a commercial wet-chemical instrument based on Hantzsch fluorimetry (R<sup>2</sup> = 0.769). The combined light source based on Y-type fiber bundle overcomes the difficulty of measuring ambient HCHO via IBBCEAS in near-ultraviolet range, which may extend IBBCEAS technology to measure other atmospheric trace gases with high precision.</p>

scholarly journals Characterization of a chemical modulation reactor (CMR) for the measurement of atmospheric concentrations of hydroxyl radicals with a laser-induced fluorescence instrument

2020 ◽  
Author(s):  
Changmin Cho ◽  
Andreas Hofzumahaus ◽  
Hendrik Fuchs ◽  
Hans-Peter Dorn ◽  
Marvin Glowania ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Trace Gases ◽  
Ambient Air ◽  
Laser Induced Fluorescence ◽  
Optical Absorption Spectroscopy ◽  
Oh Radicals ◽  
Atmospheric Conditions ◽  
Atmospheric Measurements ◽  
Chemical Modulation ◽  
Scavenging Efficiency

Abstract. Precise and accurate hydroxyl radical (OH) measurements are essential to investigate how trace gases are oxidized and transformed in the troposphere and how secondary pollutants like ozone (O3) are formed. Laser induced fluorescence (LIF) is a widely used technique for the measurement of ambient OH radicals and was used for the majority of field campaigns and chamber experiments. Recently, most LIF instruments in use for atmospheric measurements of OH radicals introduced chemical modulation to separate the ambient OH radical concentration from possible interferences by chemically removing ambient OH radicals before they enter the detection cell. In this study, we describe the application, characterization, and validation of a chemical modulation reactor (CMR) applied to the Forschungszentrum Jülich LIF (FZJ-LIF) instrument in use at the atmospheric simulation chamber SAPHIR. Besides dedicated experiments in synthetic air, the new technique was extensively tested during the year-round Jülich Atmospheric Chemistry Project (JULIAC) campaign, in which ambient air was continuously flowed into the SAPHIR chamber. It allowed performing OH measurement comparisons with Differential Optical Absorption Spectroscopy (DOAS) and investigation of interferences in a large variety of chemical and meteorological conditions. A good agreement was obtained in the LIF DOAS intercomparison within instrumental accuracies (18 % for LIF, 6.5 % for DOAS) which confirms that the new chemical modulation system of the FZJ-LIF instrument is suitable for measurement of interference-free OH concentrations. Known interferences from O3 + H2O and the nitrate radical (NO3) were quantified with the CMR in synthetic air in the chamber and found to be 3.0 × 105 cm-3 and 0.6 × 105 cm-3, respectively, for typical ambient air condition (O3 = 50 ppbv, H2O = 1 %, NO3 = 10 pptv). The interferences measured in ambient air during the JULIAC campaign in summer season had the median diurnal variation of the interference with a maximum daytime value of 0.9 × 106 cm-3 and a minimum nighttime value of 0.4 × 106 cm-3. The highest interference of 2 × 106 cm-3 occurred in a heat wave from 22–29 August, when the air temperature and ozone increased to 40 °C and 100 ppbv, respectively. All observed interferences could be fully explained by the known O3 + H2O interference, which is routinely corrected in FZJ-LIF measurements when no chemical modulation is applied. No evidence for unexplained interference was found during the JULIAC campaign. A kinetic chemical model of the chemical modulation reactor was developed and applied to estimate the possible perturbation of the OH transmission and scavenging efficiency by reactive atmospheric trace gases. These can remove OH by gas phase reactions in the reactor, or produce OH by non-photolytical reactions, most importantly by the reaction of ambient HO2 with NO. The interfering processes become relevant at high atmospheric OH reactivities. For the conditions of the JULIAC campaign with OH reactivities below 20 s-1, the influence on the determination of ambient OH concentrations was small (on average: 2 %). However, in environments with high OH reactivities, such as in a rain forest or megacity, the expected perturbation in the currently used chemical modulation reactor could be large (more than a factor of 2) and would need careful analysis and correction. This implies that chemical modulation, which was developed to eliminate interferences in ambient OH measurements, itself can be subject to interferences that depend on ambient atmospheric conditions.

scholarly journals Characterization of a chemical modulation reactor (CMR) for the measurement of atmospheric concentrations of hydroxyl radicals with a laser-induced fluorescence instrument

2021 ◽  
Vol 14 (3) ◽  
pp. 1851-1877
Author(s):  
Changmin Cho ◽  
Andreas Hofzumahaus ◽  
Hendrik Fuchs ◽  
Hans-Peter Dorn ◽  
Marvin Glowania ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Trace Gases ◽  
Ambient Air ◽  
Laser Induced Fluorescence ◽  
Optical Absorption Spectroscopy ◽  
Oh Radicals ◽  
Atmospheric Measurements ◽  
Chemical Modulation ◽  
Scavenging Efficiency

Abstract. Precise and accurate hydroxyl radical (OH) measurements are essential to investigate mechanisms for oxidation and transformation of trace gases and processes leading to the formation of secondary pollutants like ozone (O3) in the troposphere. Laser-induced fluorescence (LIF) is a widely used technique for the measurement of ambient OH radicals and was used for the majority of field campaigns and chamber experiments. Recently, most LIF instruments in use for atmospheric measurements of OH radicals introduced chemical modulation to separate the ambient OH radical concentration from possible interferences by chemically removing ambient OH radicals before they enter the detection cell (Mao et al., 2012; Novelli et al., 2014a). In this study, we describe the application and characterization of a chemical modulation reactor (CMR) applied to the Forschungszentrum Jülich LIF (FZJ-LIF) instrument in use at the atmospheric simulation chamber SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction Chamber). Besides dedicated experiments in synthetic air, the new technique was extensively tested during the year-round Jülich Atmospheric Chemistry Project (JULIAC) campaign, in which ambient air was continuously flowed into the SAPHIR chamber. It allowed for performing OH measurement comparisons with differential optical absorption spectroscopy (DOAS) and investigation of interferences in a large variety of chemical and meteorological conditions. Good agreement was obtained in the LIF–DOAS intercomparison within instrumental accuracies (18 % for LIF and 6.5 % for DOAS) which confirms that the new chemical modulation system of the FZJ-LIF instrument is suitable for measurement of interference-free OH concentrations under the conditions of the JULIAC campaign (rural environment). Known interferences from O3+H2O and the nitrate radical (NO3) were quantified with the CMR in synthetic air in the chamber and found to be 3.0×105 and 0.6×105 cm−3, respectively, for typical ambient-air conditions (O3=50 ppbv, H2O = 1 % and NO3=10 pptv). The interferences measured in ambient air during the JULIAC campaign in the summer season showed a median diurnal variation with a median maximum value of 0.9×106 cm−3 during daytime and a median minimum value of 0.4×106 cm−3 at night. The highest interference of 2×106 cm−3 occurred in a heat wave from 22 to 29 August, when the air temperature and ozone increased to 40 ∘C and 100 ppbv, respectively. All observed interferences could be fully explained by the known O3+H2O interference, which is routinely corrected in FZJ-LIF measurements when no chemical modulation is applied. No evidence for an unexplained interference was found during the JULIAC campaign. A chemical model of the CMR was developed and applied to estimate the possible perturbation of the OH transmission and scavenging efficiency by reactive atmospheric trace gases. These can remove OH by gas phase reactions in the CMR or produce OH by non-photolytic reactions, most importantly by the reaction of ambient HO2 with NO. The interfering processes become relevant at high atmospheric OH reactivities. For the conditions of the JULIAC campaign with OH reactivities below 20 s−1, the influence on the determination of ambient OH concentrations was small (on average: 2 %). However, in environments with high OH reactivities, such as in a rain forest or megacity, the expected perturbation in the currently used chemical modulation reactor could be large (more than a factor of 2). Such perturbations need to be carefully investigated and corrected for the proper evaluation of OH concentrations when applying chemical scavenging. This implies that chemical modulation, which was developed to eliminate interferences in ambient OH measurements, itself can be subject to interferences that depend on ambient atmospheric conditions.

scholarly journals Atmospheric OH reactivities in the Pearl River Delta – China in summer 2006: measurement and model results

2010 ◽  
Vol 10 (22) ◽  
pp. 11243-11260 ◽  
Author(s):  
S. Lou ◽  
F. Holland ◽  
F. Rohrer ◽  
K. Lu ◽  
B. Bohn ◽  
...  
Keyword(s):  
Organic Compounds ◽  
Atmospheric Chemistry ◽  
Pearl River Delta ◽  
Trace Gases ◽  
Ambient Air ◽  
River Delta ◽  
Rural Site ◽  
Pearl River ◽  
Secondary Chemistry ◽  
Model Calculations

Abstract. Total atmospheric OH reactivities (kOH) have been measured as reciprocal OH lifetimes by a newly developed instrument at a rural site in the densely populated Pearl River Delta (PRD) in Southern China in summer 2006. The deployed technique, LP-LIF, uses laser flash photolysis (LP) for artificial OH generation and laser-induced fluorescence (LIF) to measure the time-dependent OH decay in samples of ambient air. The reactivities observed at PRD covered a range from 10 s−1 to 120 s−1, indicating a large load of chemical reactants. On average, kOH exhibited a pronounced diurnal profile with a mean maximum value of 50 s−1 at daybreak and a mean minimum value of 20 s−1 at noon. The comparison of reactivities calculated from measured trace gases with measured kOH reveals a missing reactivity of about a factor of 2 at day and night. The reactivity explained by measured trace gases was dominated by anthropogenic pollutants (e.g., CO, NOx, light alkenes and aromatic hydrocarbons) at night, while it was strongly influenced by local, biogenic emissions of isoprene during the day. Box model calculations initialized by measured parameters reproduce the observed OH reactivity well and suggest that the missing reactivity is contributed by unmeasured, secondary chemistry products (mainly aldehydes and ketones) that were photochemically formed by hydrocarbon oxidation. Overall, kOH was dominated by organic compounds, which had a maximum contribution of 85% in the afternoon. The paper demonstrates the usefulness of direct reactivity measurements, emphasizes the need for direct measurements of oxygenated organic compounds in atmospheric chemistry studies, and discusses uncertainties of the modelling of OVOC reactivities.

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