scholarly journals Development of a Laser-Photofragmentation Laser-Induced Fluorescence instrument for the detection of nitrous acid and hydroxyl radicals in the atmosphere

2021 ◽  
Author(s):  
Brandon Bottorff ◽  
Emily Reidy ◽  
Levi Mielke ◽  
Sebastien Dusanter ◽  
Philip Stevens
Keyword(s):  
Hydroxyl Radicals ◽  
Nitrous Acid ◽  
Laser Induced Fluorescence ◽  
Urban Setting ◽  
Integration Time ◽  
Oh Radical ◽  
Fragmentation Efficiency ◽  
Expansion Technique ◽  
New Instrument ◽  
Radical Fragment

Abstract. A new instrument for the measurement of atmospheric nitrous acid (HONO) and hydroxyl radicals (OH) has been developed using laser photofragmentation (LP) of HONO at 355 nm after expansion into a low-pressure cell, followed by resonant laser-induced fluorescence (LIF) of the resulting OH radical fragment at 308 nm similar to the fluorescence assay by gas expansion technique (FAGE). The LP/LIF instrument is calibrated by determining the photo-fragmentation efficiency of HONO. In this method, a known concentration of OH from the photo-dissociation of water vapor is titrated with nitric oxide to produce a known concentration of HONO. Measurement of the concentration of the OH radical fragment relative to the concentration of HONO provides a measurement of the photo-fragmentation efficiency. The LP/LIF instrument has demonstrated a 1σ detection limit of 9 ppt for a 10-min integration time. Ambient measurements of HONO and OH from a forested environment and an urban setting are presented along with indoor measurements to demonstrate the performance of the instrument.

scholarly journals Development of a laser-photofragmentation laser-induced fluorescence instrument for the detection of nitrous acid and hydroxyl radicals in the atmosphere

2021 ◽  
Vol 14 (9) ◽  
pp. 6039-6056
Author(s):  
Brandon Bottorff ◽  
Emily Reidy ◽  
Levi Mielke ◽  
Sebastien Dusanter ◽  
Philip S. Stevens
Keyword(s):  
Hydroxyl Radicals ◽  
Nitrous Acid ◽  
Laser Induced Fluorescence ◽  
Urban Setting ◽  
Integration Time ◽  
Oh Radical ◽  
Expansion Technique ◽  
New Instrument ◽  
Gas Expansion ◽  
Radical Fragment

Abstract. A new instrument for the measurement of atmospheric nitrous acid (HONO) and hydroxyl radicals (OH) has been developed using laser photofragmentation (LP) of HONO at 355 nm after expansion into a low-pressure cell, followed by resonant laser-induced fluorescence (LIF) of the resulting OH radical fragment at 308 nm similar to the fluorescence assay by gas expansion technique (FAGE). The LP/LIF instrument is calibrated by determining the photofragmentation efficiency of HONO and calibrating the instrument sensitivity for detection of the OH fragment. In this method, a known concentration of OH from the photo-dissociation of water vapor is titrated with nitric oxide to produce a known concentration of HONO. Measurement of the concentration of the OH radical fragment relative to the concentration of HONO provides a measurement of the photofragmentation efficiency. The LP/LIF instrument has demonstrated a 1σ detection limit for HONO of 9 ppt for a 10 min integration time. Ambient measurements of HONO and OH from a forested environment and an urban setting are presented along with indoor measurements to demonstrate the performance of the instrument.

scholarly journals Characterisation of an inlet pre-injector laser induced fluorescence instrument for the measurement of ambient hydroxyl radicals

2014 ◽  
Vol 7 (1) ◽  
pp. 819-858 ◽  
Author(s):  
A. Novelli ◽  
K. Hens ◽  
C. Tatum Ernest ◽  
D. Kubistin ◽  
E. Regelin ◽  
...  
Keyword(s):  
Hydroxyl Radicals ◽  
Analytical Techniques ◽  
Laser Induced Fluorescence ◽  
High Reactivity ◽  
Measurement Unit ◽  
Mass Spectrometers ◽  
Expansion Technique ◽  
Sustained Effort ◽  
Gas Expansion ◽  
Ambient Measurements

Abstract. Ambient measurements of hydroxyl radicals (OH) are challenging due to a high reactivity and consequently low concentration. The importance of OH as an atmospheric oxidant has resulted in a sustained effort leading to the development of a number of analytical techniques. Recent work has indicated that the laser-induced fluorescence of the OH molecules method based on the fluorescence assay by gas expansion technique (LIF-FAGE) for the measurement of atmospheric OH in some environments may be influenced by artificial OH generated within the instrument, and a chemical method to remove this interference was implemented in a LIF-FAGE system by Mao et al. (2012). We have applied this method to our LIF-FAGE HORUS (HydrOxyl Radical Measurement Unit based on fluorescence Spectroscopy) system, and developed and deployed an inlet pre-injector (IPI) to determine the chemical zero level in the instrument via scavenging the ambient OH radical. We describe and characterise this technique in addition to its application at field sites in forested locations in Finland, Spain, and Germany. Ambient measurements show that OH generated within the HORUS instrument is a non-negligible fraction of the total OH signal, which can comprise 30% to 80% during the day and 60% to 100% during the night. The contribution of the background OH varied greatly between measurement sites and was likely related to the type and concentration of volatile organic compounds (VOCs) present at each particular location. Two inter-comparisons in contrasting environments between the HORUS instrument and two different chemical ionisation mass spectrometers (CIMS) are described to demonstrate the efficacy of the inlet-pre-injector and the necessity of the chemical zeroing method in such environments.

scholarly journals Characterisation of an inlet pre-injector laser-induced fluorescence instrument for the measurement of atmospheric hydroxyl radicals

2014 ◽  
Vol 7 (10) ◽  
pp. 3413-3430 ◽  
Author(s):  
A. Novelli ◽  
K. Hens ◽  
C. Tatum Ernest ◽  
D. Kubistin ◽  
E. Regelin ◽  
...  
Keyword(s):  
Hydroxyl Radicals ◽  
Analytical Techniques ◽  
Laser Induced Fluorescence ◽  
High Reactivity ◽  
Measurement Unit ◽  
Atmospheric Measurements ◽  
Mass Spectrometers ◽  
Expansion Technique ◽  
Highly Sensitive ◽  
Gas Expansion

Abstract. Atmospheric measurements of hydroxyl radicals (OH) are challenging due to a high reactivity and consequently low concentration. The importance of OH as an atmospheric oxidant has motivated a sustained effort leading to the development of a number of highly sensitive analytical techniques. Recent work has indicated that the laser-induced fluorescence of the OH molecules method based on the fluorescence assay by gas expansion technique (LIF-FAGE) for the measurement of atmospheric OH in some environments may be influenced by artificial OH generated within the instrument, and a chemical method to remove this interference was implemented in a LIF-FAGE system by Mao et al. (2012). While it is not clear whether other LIF-FAGE instruments suffer from the same interference, we have applied this method to our LIF-FAGE HORUS (Hydroxyl Radical Measurement Unit based on fluorescence Spectroscopy) system, and developed and deployed an inlet pre-injector (IPI) to determine the chemical zero level in the instrument via scavenging the ambient OH radical. We describe and characterise this technique in addition to its application at field sites in forested locations in Finland, Spain and Germany. Ambient measurements show that OH generated within the HORUS instrument is a non-negligible fraction of the total OH signal, which can comprise 30 to 80% during daytime and 60 to 100% during the night. The contribution of the background OH varied greatly between measurement sites and was likely related to the type and concentration of volatile organic compounds (VOCs) present at each particular location. Two inter-comparisons in contrasting environments between the HORUS instrument and two different chemical ionisation mass spectrometers (CIMS) are described to demonstrate the efficacy of IPI and the necessity of the chemical zeroing method for our LIF-FAGE instrument in such environments.

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.

scholarly journals Development and application of a new mobile LOPAP instrument for the measurement of HONO altitude profiles in the planetary boundary layer

2009 ◽  
Vol 2 (4) ◽  
pp. 2027-2054 ◽  
Author(s):  
R. Häseler ◽  
T. Brauers ◽  
F. Holland ◽  
A. Wahner
Keyword(s):  
Nitrous Acid ◽  
Ground Level ◽  
Concentration Profiles ◽  
Mixing Ratio ◽  
Above Ground Level ◽  
Mixing Ratios ◽  
New Instrument ◽  
Mobile Measurements ◽  
Southwest Germany ◽  
Absorption Technique

Abstract. The LOPAP (long path absorption) technique has been shown to be very sensitive for the detection of nitrous acid (HONO) in the atmosphere. However, current instruments were mainly built for ground based applications. Therefore, we designed a new LOPAP instrument to be more versatile for mobile measurements and to meet the requirements for airborne application. The detection limit of the new instrument is below 1 ppt at a time resolution of 5 to 7 min. As a first test, the instrument was successfully employed during the ZEPTER-1 campaign in July 2007 on board of the Zeppelin NT airship. During 15 flights on six days we measured HONO concentration profiles over southwest Germany, predominantly in the range between 100 m and 650 m above ground level. On average, a mixing ratio of 34 ppt was observed, almost independently of height. Within a econd campaign, ZEPTER-2 in fall 2008, higher HONO mixing ratios were observed in the Lake Constance area.

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