scholarly journals Characterisation of the photolytic HONO-source in the atmosphere simulation chamber SAPHIR

2005 ◽  
Vol 5 (8) ◽  
pp. 2189-2201 ◽  
Author(s):  
F. Rohrer ◽  
B. Bohn ◽  
T. Brauers ◽  
D. Brüning ◽  
F.-J. Johnen ◽  
...  
Keyword(s):  
Adsorbed Water ◽  
Ambient Air ◽  
Solar Irradiation ◽  
Oh Radical ◽  
Nox Formation ◽  
Empirical Function ◽  
Glass Surfaces ◽  
Atmospheric Concentrations ◽  
Atmosphere Simulation Chamber ◽  
Simulation Chamber

Abstract. HONO formation has been proposed as an important OH radical source in simulation chambers for more than two decades. Besides the heterogeneous HONO formation by the dark reaction of NO2 and adsorbed water, a photolytic source has been proposed to explain the elevated reactivity in simulation chamber experiments. However, the mechanism of the photolytic process is not well understood so far. As expected, production of HONO and NOx was also observed inside the new atmospheric simulation chamber SAPHIR under solar irradiation. This photolytic HONO and NOx formation was studied with a sensitive HONO instrument under reproducible controlled conditions at atmospheric concentrations of other trace gases. It is shown that the photolytic HONO source in the SAPHIR chamber is not caused by NO2 reactions and that it is the only direct NOy source under illuminated conditions. In addition, the photolysis of nitrate which was recently postulated for the observed photolytic HONO formation on snow, ground, and glass surfaces, can be excluded in the chamber. A photolytic HONO source at the surface of the chamber is proposed which is strongly dependent on humidity, on light intensity, and on temperature. An empirical function describes these dependencies and reproduces the observed HONO formation rates to within 10%. It is shown that the photolysis of HONO represents the dominant radical source in the SAPHIR chamber for typical tropospheric O3/H2O concentrations. For these conditions, the HONO concentrations inside SAPHIR are similar to recent observations in ambient air.

scholarly journals Characterisation of the photolytic HONO-source in the atmosphere simulation chamber SAPHIR

2004 ◽  
Vol 4 (6) ◽  
pp. 7881-7915 ◽  
Author(s):  
F. Rohrer ◽  
B. Bohn ◽  
T. Brauers ◽  
D. Brüning ◽  
F.-J. Johnen ◽  
...  
Keyword(s):  
Adsorbed Water ◽  
Ambient Air ◽  
Solar Irradiation ◽  
Oh Radical ◽  
Nox Formation ◽  
Empirical Function ◽  
Glass Surfaces ◽  
Atmospheric Concentrations ◽  
Atmosphere Simulation Chamber ◽  
Simulation Chamber

Abstract. HONO formation has been proposed as an important OH radical source in simulation chambers for more than two decades. Besides the heterogeneous HONO formation by the dark reaction of NO2 and adsorbed water, a photolytic source has been proposed to explain the elevated reactivity in simulation chamber experiments. However, the mechanism of the photolytic process is not well understood so far. As expected, production of HONO and NOx was also observed inside the new atmosphere simulation chamber SAPHIR under solar irradiation. This photolytic HONO and NOx formation was studied with a sensitive HONO instrument under reproducible controlled conditions at atmospheric concentrations of other trace gases. It is shown that the photolytic HONO source in the SAPHIR chamber is not caused by NO2 reactions and that it is the only direct NOy source under illuminated conditions. In addition, the photolysis of nitrate which was recently postulated for the observed photolytic HONO formation on snow, ground, and glass surfaces, can be excluded in the chamber. A photolytic HONO source at the surface of the chamber is proposed which is strongly dependent on humidity, on light intensity, and on temperature. An empirical function of the form S(HONO)=a1,2×J(NO2)×(1+(RH/RH0)2)×exp(−T0/T) describes these dependencies and reproduces the observed HONO formation rates to within 10%. It is shown that the photolysis of HONO represents the dominant radical source in the SAPHIR chamber for typical tropospheric O3/H2O concentrations. For these conditions, the HONO concentrations inside SAPHIR are similar to recent observations in ambient air.

scholarly journals Atmospheric photochemistry of aromatic hydrocarbons: OH budgets during SAPHIR chamber experiments

2014 ◽  
Vol 14 (13) ◽  
pp. 6941-6952 ◽  
Author(s):  
S. Nehr ◽  
B. Bohn ◽  
H.-P. Dorn ◽  
H. Fuchs ◽  
R. Häseler ◽  
...  
Keyword(s):  
Aromatic Hydrocarbons ◽  
Oh Radical ◽  
Reference Compound ◽  
Photo Oxidation ◽  
Average Ratio ◽  
Budget Analysis ◽  
Benzene Toluene ◽  
Experimental Errors ◽  
Atmosphere Simulation Chamber ◽  
Simulation Chamber

Abstract. Current photochemical models developed to simulate the atmospheric degradation of aromatic hydrocarbons tend to underestimate OH radical concentrations. In order to analyse OH budgets, we performed experiments with benzene, toluene, p-xylene and 1,3,5-trimethylbenzene in the atmosphere simulation chamber SAPHIR. Experiments were conducted under low-NO conditions (typically 0.1–0.2 ppb) and high-NO conditions (typically 7–8 ppb), and starting concentrations of 6–250 ppb of aromatics, dependent on OH rate constants. For the OH budget analysis a steady-state approach was applied in which OH production and destruction rates (POH and DOH) have to be equal. The POH were determined from measurements of HO2, NO, HONO, and O3 concentrations, considering OH formation by photolysis and recycling from HO2. The DOH were calculated from measurements of the OH concentrations and total OH reactivities. The OH budgets were determined from DOH/POH ratios. The accuracy and reproducibility of the approach were assessed in several experiments using CO as a reference compound where an average ratio DOH/POH = 1.13 ± 0.19 was obtained. In experiments with aromatics, these ratios ranged within 1.1–1.6 under low-NO conditions and 0.9–1.2 under high-NO conditions. The results indicate that OH budgets during photo-oxidation experiments with aromatics are balanced within experimental accuracies. Inclusion of a further, recently proposed OH production via HO2 + RO2 reactions led to improvements under low-NO conditions but the differences were small and insignificant within the experimental errors.

scholarly journals Technical Note: Intercomparison of formaldehyde measurements at the atmosphere simulation chamber SAPHIR

2007 ◽  
Vol 7 (6) ◽  
pp. 15619-15650 ◽  
Author(s):  
A. Wisthaler ◽  
E.C. Apel ◽  
J. Bossmeyer ◽  
A. Hansel ◽  
W. Junkermann ◽  
...  
Keyword(s):  
Ambient Air ◽  
Proton Transfer Reaction ◽  
Technical Note ◽  
Research Centre ◽  
Mixing Ratios ◽  
Analytical Instruments ◽  
Chamber Volume ◽  
Set Up ◽  
Atmosphere Simulation Chamber ◽  
Simulation Chamber

Abstract. The atmosphere simulation chamber SAPHIR at the Research Centre Jülich was used to test the suitability of state-of-the-art analytical instruments for the measurement of gas-phase formaldehyde (HCHO) in air. Five analyzers based on four different sensing principles were deployed: a differential optical absorption spectrometer (DOAS), cartridges for 2,4-dinitro-phenyl-hydrazine (DNPH) derivatization followed by off-line high pressure liquid chromatography (HPLC) analysis, two different types of commercially available wet chemical sensors based on Hantzsch fluorimetry, and a proton-transfer-reaction mass spectrometer (PTR-MS). A new optimized mode of operation was used for the PTR-MS instrument which significantly enhanced its performance for on-line HCHO detection at low absolute humidities. The instruments were challenged with typical ambient levels of HCHO ranging from zero to several ppb. Synthetic air of high purity and particulate-filtered ambient air were used as sample matrices in the atmosphere simulation chamber onto which HCHO was spiked under varying levels of humidity and ozone. Measurements were compared to mixing ratios calculated from the chamber volume and the known amount of HCHO injected into the chamber; measurements were also compared between the different instruments. The formal and blind intercomparison exercise was conducted under the control of an independent referee. A number of analytical problems associated with the experimental set-up and with individual instruments were identified, the overall agreement between the methods was good.

scholarly journals Atmospheric photochemistry of aromatic hydrocarbons: OH budgets during SAPHIR chamber experiments

2014 ◽  
Vol 14 (5) ◽  
pp. 5535-5560 ◽  
Author(s):  
S. Nehr ◽  
B. Bohn ◽  
H.-P. Dorn ◽  
H. Fuchs ◽  
R. Häseler ◽  
...  
Keyword(s):  
Aromatic Hydrocarbons ◽  
Oh Radical ◽  
Reference Compound ◽  
Photo Oxidation ◽  
Average Ratio ◽  
Budget Analysis ◽  
Benzene Toluene ◽  
Experimental Errors ◽  
Atmosphere Simulation Chamber ◽  
Simulation Chamber

Abstract. Current photochemical models developed to simulate the atmospheric degradation of aromatic hydrocarbons tend to underestimate OH radical concentrations. In order to analyse OH budgets, we performed experiments with benzene, toluene, p-xylene, and 1,3,5-trimethylbenzene in the atmosphere simulation chamber SAPHIR. Experiments were conducted under low-NO conditions (typically 0.1–0.2 ppb) and high-NO conditions (typically 7–8 ppb), and starting concentrations of 6–250 ppb of aromatics, dependent on OH rate constants. For the OH budget analysis a steady-state approach was applied where OH production and destruction rates (POH and DOH) have to be equal. The POH were determined from measurements of HO2, NO, HONO, and O3 concentrations, considering OH formation by photolysis and recycling from HO2. The DOH were calculated from measurements of the OH concentrations and total OH reactivities. The OH budgets were determined from DOH / POH ratios. The accuracy and reproducibility of the approach were assessed in several experiments using CO as a reference compound where an average ratio DOH / POH = 1.13 ± 0.19 was obtained. In experiments with aromatics, these ratios ranged within 1.1–1.6 under low-NO conditions and 0.9–1.2 under high-NO conditions. The results indicate that OH budgets during photo-oxidation experiments with aromatics are balanced within experimental accuracies. Inclusion of a further, recently proposed OH production via HO2 + RO2 reactions led to improvements under low-NO conditions but the differences were small and insignificant within the experimental errors.

scholarly journals Technical Note: Formal blind intercomparison of HO<sub>2</sub> measurements in the atmosphere simulation chamber SAPHIR during the HOxComp campaign

2010 ◽  
Vol 10 (24) ◽  
pp. 12233-12250 ◽  
Author(s):  
H. Fuchs ◽  
T. Brauers ◽  
H.-P. Dorn ◽  
H. Harder ◽  
R. Häseler ◽  
...  
Keyword(s):  
Water Vapor ◽  
Correlation Coefficients ◽  
Chemical Conversion ◽  
Ambient Air ◽  
Technical Note ◽  
Data Set ◽  
Air Masses ◽  
Regression Parameters ◽  
Atmosphere Simulation Chamber ◽  
Simulation Chamber

Abstract. Hydroperoxy radical (HO2) concentrations were measured during the formal blind intercomparison campaign HOxComp carried out in Jülich, Germany, in 2005. Three instruments detected HO2 via chemical conversion to hydroxyl radicals (OH) and subsequent detection of the sum of OH and HO2 by laser induced fluorescence (LIF). All instruments were based on the same detection and calibration scheme. Because measurements by a MIESR instrument failed during the campaign, no absolute reference measurement was available, so that the accuracy of individual instruments could not be addressed. Instruments sampled ambient air for three days and were attached to the atmosphere simulation chamber SAPHIR during the second part of the campaign. Six experiments of one day each were conducted in SAPHIR, where air masses are homogeneously mixed, in order to investigate the performance of instruments and to determine potential interferences of measurements under well-controlled conditions. Linear correlation coefficients (R2) between measurements of the LIF instruments are generally high and range from 0.82 to 0.98. However, the agreement between measurements is variable. The regression analysis of the entire data set of measurements in SAPHIR yields slopes between 0.69 to 1.26 and intercepts are smaller than typical atmospheric daytime concentrations (less than 1 pptv). The quality of fit parameters improves significantly, when data are grouped into data subsets of similar water vapor concentrations. Because measurements of LIF instruments were corrected for a well-characterized water dependence of their sensitivities, this indicates that an unknown factor related to water vapor affected measurements in SAPHIR. Measurements in ambient air are also well-correlated, but regression parameters differ from results obtained from SAPHIR experiments. This could have been caused by differences in HO2 concentrations in the sampled air at the slightly different locations of instruments.

scholarly journals Technical Note: Formal blind intercomparison of HO<sub>2</sub> measurements in the atmosphere simulation chamber SAPHIR during the HOxComp campaign

2010 ◽  
Vol 10 (9) ◽  
pp. 21189-21235 ◽  
Author(s):  
H. Fuchs ◽  
T. Brauers ◽  
H.-P. Dorn ◽  
H. Harder ◽  
R. Häseler ◽  
...  
Keyword(s):  
Water Vapor ◽  
Correlation Coefficients ◽  
Chemical Conversion ◽  
Ambient Air ◽  
Technical Note ◽  
Data Set ◽  
Air Masses ◽  
Regression Parameters ◽  
Atmosphere Simulation Chamber ◽  
Simulation Chamber

Abstract. Hydroperoxy radical (HO2) concentrations were measured during the formal blind intercomparison campaign HOxComp carried out in Jülich, Germany. Three instruments detected HO2 via chemical conversion to hydroxyl radicals (OH) and subsequent detection of the sum of OH and HO2 by laser induced fluorescence (LIF). Instruments sampled ambient air for three days and were attached to the atmosphere simulation chamber SAPHIR during the second part of the campaign. Six experiments of one day each were conducted in SAPHIR, where air masses were homogeneously mixed, in order to investigate the performance of instruments and to determine potential interferences of measurements under well-controlled conditions. Linear correlation coefficients between measurements of the LIF instruments are generally high and range from 0.82 to 0.98. However, the agreement between measurements is variable. The regression analysis of the entire data set of measurements in SAPHIR yields slopes between 0.69 to 1.26 and intercepts are smaller than typical atmospheric daytime concentrations (less than 1 pptv). The quality of fit parameters improves significantly, when data are grouped into data subsets of similar water vapor concentrations. Because measurements of LIF instruments were corrected for a well-characterized water dependence of their sensitivities, this indicates that an unknown factor related to water vapor affected measurements in SAPHIR. Measurements in ambient air are also well correlated, but regression parameters differ from results obtained from SAPHIR experiments. This is most likely caused by sampling different air masses at the slightly distant locations of instruments.

scholarly journals Technical Note: Intercomparison of formaldehyde measurements at the atmosphere simulation chamber SAPHIR

2008 ◽  
Vol 8 (8) ◽  
pp. 2189-2200 ◽  
Author(s):  
A. Wisthaler ◽  
E. C. Apel ◽  
J. Bossmeyer ◽  
A. Hansel ◽  
W. Junkermann ◽  
...  
Keyword(s):  
Ambient Air ◽  
Proton Transfer Reaction ◽  
Technical Note ◽  
Research Centre ◽  
Mixing Ratios ◽  
Analytical Instruments ◽  
Chamber Volume ◽  
Set Up ◽  
Atmosphere Simulation Chamber ◽  
Simulation Chamber

Abstract. The atmosphere simulation chamber SAPHIR at the Research Centre Jülich was used to test the suitability of state-of-the-art analytical instruments for the measurement of gas-phase formaldehyde (HCHO) in air. Five analyzers based on four different sensing principles were deployed: a differential optical absorption spectrometer (DOAS), cartridges for 2,4-dinitrophenylhydrazine (DNPH) derivatization followed by off-line high pressure liquid chromatography (HPLC) analysis, two different types of commercially available wet chemical sensors based on Hantzsch fluorimetry, and a proton-transfer-reaction mass spectrometer (PTR-MS). A new optimized mode of operation was used for the PTR-MS instrument which significantly enhanced its performance for online HCHO detection at low absolute humidities. The instruments were challenged with typical ambient levels of HCHO ranging from zero to several ppb. Synthetic air of high purity and particulate-filtered ambient air were used as sample matrices in the atmosphere simulation chamber onto which HCHO was spiked under varying levels of humidity and ozone. Measurements were compared to mixing ratios calculated from the chamber volume and the known amount of HCHO injected into the chamber; measurements were also compared between the different instruments. The formal and blind intercomparison exercise was conducted under the control of an independent referee. A number of analytical problems associated with the experimental set-up and with individual instruments were identified, the overall agreement between the methods was fair.

Investigating the NO-dependent photooxidation of limonene by OH and O3 using the atmosphere simulation chamber SAPHIR

2021 ◽  
Author(s):  
Yat Sing Pang ◽  
Martin Kaminski ◽  
Anna Novelli ◽  
Philip Carlsson ◽  
Ismail-Hakki Acir ◽  
...  
Keyword(s):  
Organic Aerosol ◽  
Oxidation Products ◽  
Chemical Mechanism ◽  
Reaction Pathways ◽  
Oh Radicals ◽  
Oh Radical ◽  
Simulation Experiments ◽  
Master Chemical Mechanism ◽  
Simulation Results ◽  
Atmosphere Simulation Chamber

&lt;p&gt;Limonene is the fourth-most abundant monoterpene in the atmosphere, which upon oxidation leads to the formation of secondary organic aerosol (SOA) and thereby influences climate and air quality.&lt;/p&gt;&lt;p&gt;In this study, the oxidation of limonene by OH at different atmospherically relevant NO and HO&lt;sub&gt;2&lt;/sub&gt; levels (NO: 0.1 &amp;#8211; 10 ppb; HO&lt;sub&gt;2&lt;/sub&gt;: 20 ppt) was investigated in simulation experiments in the SAPHIR chamber at Forschungszentrum J&amp;#252;lich. The analysis focuses on comparing measured radical concentrations (RO&lt;sub&gt;2&lt;/sub&gt;, HO&lt;sub&gt;2&lt;/sub&gt;, OH) and OH reactivity (k&lt;sub&gt;OH&lt;/sub&gt;) with modeled values calculated using the Master Chemical Mechanism (MCM) version 3.3.1.&lt;/p&gt;&lt;p&gt;At high and medium NO concentrations, RO&lt;sub&gt;2&lt;/sub&gt; is expected to quickly react with NO. An HO&lt;sub&gt;2&lt;/sub&gt; radical is produced during the process that can be converted back to an OH radical by another reaction with NO. Consistently, for experiments conducted at medium NO levels (~0.5 ppb, RO&lt;sub&gt;2&lt;/sub&gt; lifetime ~10 s), simulated RO&lt;sub&gt;2&lt;/sub&gt;, HO&lt;sub&gt;2&lt;/sub&gt;, and OH agree with observations within the measurement uncertainties, if the OH reactivity of oxidation products is correctly described.&lt;/p&gt;&lt;p&gt;At lower NO concentrations, the regeneration of HO&lt;sub&gt;2&lt;/sub&gt; in the RO&lt;sub&gt;2&lt;/sub&gt; + NO reaction is slow and the reaction of RO&lt;sub&gt;2&lt;/sub&gt; with HO&lt;sub&gt;2&lt;/sub&gt; gains importance in forming peroxides. However, simulation results show a large discrepancy between calculated radical concentrations and measurements at low NO levels (&lt;0.1 ppb, RO&lt;sub&gt;2&lt;/sub&gt; lifetime ~ 100 s). Simulated RO&lt;sub&gt;2&lt;/sub&gt; concentrations are found to be overestimated by a factor of three; simulated HO&lt;sub&gt;2&lt;/sub&gt; concentrations are underestimated by 50 %; simulated OH concentrations are underestimated by about 35%, even if k&lt;sub&gt;OH&lt;/sub&gt; is correctly described. This suggests that there could be additional RO&lt;sub&gt;2&lt;/sub&gt; reaction pathways that regenerate HO&lt;sub&gt;2&lt;/sub&gt; and OH radicals become important, but they are not taken into account in the MCM model.&lt;/p&gt;

scholarly journals Investigation of the β-pinene photooxidation by OH in the atmosphere simulation chamber SAPHIR

2016 ◽  
Author(s):  
Martin Kaminski ◽  
Hendrik Fuchs ◽  
Ismail-Hakki Acir ◽  
Birger Bohn ◽  
Theo Brauers ◽  
...  
Keyword(s):  
Degradation Mechanism ◽  
Degradation Process ◽  
Product Distribution ◽  
High Reactivity ◽  
Oxidation Products ◽  
Chemical Mechanism ◽  
Emission Rates ◽  
Photochemical Degradation ◽  
Atmosphere Simulation Chamber ◽  
Simulation Chamber

Abstract. Beside isoprene, monoterpenes are the non-methane volatile organic compounds (VOC) with the highest global emission rates. Due to their high reactivity towards OH, monoterpenes can dominate the radical chemistry of the atmosphere in forested areas. In the present study the photochemical degradation mechanism of β-pinene was investigated in the Jülich atmosphere simulation chamber SAPHIR. The focus of this study is on the OH budget in the degradation process. Therefore the SAPHIR chamber was equipped with instrumentation to measure radicals (OH, HO2, RO2), the total OH reactivity, important OH precursors (O3, HONO, HCHO), the parent VOC beta-pinene, its main oxidation products, acetone and nopinone, and photolysis frequencies. All experiments were carried out under low NOx conditions (≤ 2 ppb) and at atmospheric beta-pinene concentrations (≤ 5 ppb) with and without addition of ozone. For the investigation of the OH budget, the OH production and destruction rates were calculated from measured quantities. Within the limits of accuracy of the instruments, the OH budget was balanced in all β-pinene oxidation experiments. However, even though the OH budget was closed, simulation results from the Master Chemical Mechanism 3.2 showed that the OH production and destruction rates were underestimated by the model. The measured OH and HO2 concentrations were underestimated by up to a factor of two whereas the total OH reactivity was slightly overestimated because of the poor reproduction of the measured nopinone by the model by up to a factor of three. A new, theory-derived first-generation product distribution by Vereecken and Peeters was able to reproduce the measured nopinone time series and the total OH reactivity. Nevertheless the measured OH and HO2 concentrations remained underestimated by the numerical simulations. These observations together with the fact that the measured OH budget was closed suggest the existence of unaccounted sources of HO2.

scholarly journals Comparison of OH reactivity measurements in the atmospheric simulation chamber SAPHIR

2017 ◽  
Author(s):  
Hendrik Fuchs ◽  
Anna Novelli ◽  
Michael Rolletter ◽  
Andreas Hofzumahaus ◽  
Eva Y. Pfannerstill ◽  
...  
Keyword(s):  
Water Vapor ◽  
Organic Compounds ◽  
Limit Of Detection ◽  
Measurement Techniques ◽  
Oh Radical ◽  
Atmospheric Measurements ◽  
Radical Reactivity ◽  
Wide Range ◽  
Chemical Conditions ◽  
Simulation Chamber

Abstract. Hydroxyl (OH) radical reactivity (kOH) has been measured for 18 years with different measurement techniques. In order to compare the performances of instruments deployed in the field, two campaigns were conducted performing experiments in the atmospheric simulation chamber SAPHIR at Forschungszentrum Jülich in October 2015 and April 2016. Chemical conditions were chosen either to be representative of the atmosphere or to test potential limitations of instruments. All types of instruments that are currently used for atmospheric measurements took part in one of the two campaigns. The results of these campaigns demonstrate that OH reactivity can be accurately measured for a wide range of atmospherically relevant chemical conditions (e.g. water vapor, nitrogen oxides, various organic compounds) by all instruments. The precision of the measurements (limit of detection

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