scholarly journals Measurement of interferences associated with the detection of the hydroperoxy radical in the atmosphere using laser-induced fluorescence

2017 ◽  
Author(s):  
Michelle M. Lew ◽  
Sebastien Dusanter ◽  
Philip S. Stevens
Keyword(s):  
Laser Induced Fluorescence ◽  
Biogenic Emissions ◽  
Peroxy Radicals ◽  
Indiana University ◽  
Hydroperoxy Radical ◽  
Volatile Organic ◽  
Field Campaigns ◽  
Gas Expansion ◽  
The Impact ◽  
Ho2 Radical

Abstract. One technique used to measure concentrations of the hydroperoxy radical (HO2) in the atmosphere involves chemically converting it to OH by addition of NO and subsequent detection of OH. However, some organic peroxy radicals (RO2) can also be rapidly converted to HO2 (and subsequently OH) in the presence of NO, interfering with measurements of ambient HO2 radical concentrations. This interference must be characterized for each instrument to determine to what extent various RO2 radicals interfere with measurements of HO2 and to assess the impact of this interference on past measurements. The efficiency of RO2 to HO2 conversion for the Indiana University Laser-Induced Fluorescence – Fluorescence Assay by Gas Expansion (IU-FAGE) instrument was measured for a variety of RO2 radicals. Known quantities of OH and HO2 radicals were produced from the photolysis of water vapor at 184.9 nm, and RO2 radicals were produced by the reaction of several volatile organic compounds with OH. The conversion efficiency of RO2 radicals to HO2 was measured when NO was added to the sampling cell for conditions employed during several previous field campaigns. For these conditions, approximately 80 % of alkene derived RO2 radicals and 20 % of alkane derived RO2 radicals were converted to HO2. Based on these measurements, interferences from various RO2 radicals contributed to approximately 35 % of the measured HO2 signal during the Mexico City Metropolitan Area (MCMA) 2006 campaign, where the measured VOCs consisted of a mixture of saturated and unsaturated species. However, this interference can contribute more significantly to the measured HO2 signal in forested environments dominated by unsaturated biogenic emissions such as isoprene.

scholarly journals Measurement of interferences associated with the detection of the hydroperoxy radical in the atmosphere using laser-induced fluorescence

2018 ◽  
Vol 11 (1) ◽  
pp. 95-109 ◽  
Author(s):  
Michelle M. Lew ◽  
Sebastien Dusanter ◽  
Philip S. Stevens
Keyword(s):  
Laser Induced Fluorescence ◽  
Biogenic Emissions ◽  
Peroxy Radicals ◽  
Indiana University ◽  
Hydroperoxy Radical ◽  
Volatile Organic ◽  
Field Campaigns ◽  
Gas Expansion ◽  
The Impact ◽  
Ho2 Radical

Abstract. One technique used to measure concentrations of the hydroperoxy radical (HO2) in the atmosphere involves chemically converting it to OH by addition of NO and subsequent detection of OH. However, some organic peroxy radicals (RO2) can also be rapidly converted to HO2 (and subsequently OH) in the presence of NO, interfering with measurements of ambient HO2 radical concentrations. This interference must be characterized for each instrument to determine to what extent various RO2 radicals interfere with measurements of HO2 and to assess the impact of this interference on past measurements. The efficiency of RO2-to-HO2 conversion for the Indiana University laser-induced fluorescence–fluorescence assay by gas expansion (IU-FAGE) instrument was measured for a variety of RO2 radicals. Known quantities of OH and HO2 radicals were produced from the photolysis of water vapor at 184.9 nm, and RO2 radicals were produced by the reaction of several volatile organic compounds (VOCs) with OH. The conversion efficiency of RO2 radicals to HO2 was measured when NO was added to the sampling cell for conditions employed during several previous field campaigns. For these conditions, approximately 80 % of alkene-derived RO2 radicals and 20 % of alkane-derived RO2 radicals were converted to HO2. Based on these measurements, interferences from various RO2 radicals contributed to approximately 35 % of the measured HO2 signal during the Mexico City Metropolitan Area (MCMA) 2006 campaign (MCMA-2006), where the measured VOCs consisted of a mixture of saturated and unsaturated species. However, this interference can contribute more significantly to the measured HO2 signal in forested environments dominated by unsaturated biogenic emissions such as isoprene.

scholarly journals Measurements of the OH radical yield from the ozonolysis of biogenic alkenes: A potential interference with laser-induced fluorescence measurements of ambient OH

2017 ◽  
Author(s):  
Pamela Rickly ◽  
Philip S. Stevens
Keyword(s):  
Flow Reactor ◽  
Laser Induced Fluorescence ◽  
Fluorescence Measurements ◽  
Criegee Intermediates ◽  
Volatile Organic ◽  
Forested Areas ◽  
Rigorous Test ◽  
Reactor Operating ◽  
Gas Expansion ◽  
Radical Yield

Abstract. Reactions of the hydroxyl radical (OH) play a central role in the chemistry of the atmosphere, and measurements of its concentration can provide a rigorous test of our understanding of atmospheric oxidation. Several recent studies have shown large discrepancies between measured and modeled OH concentrations in forested areas impacted by emissions of biogenic volatile organic compounds (BVOCs), where modeled concentrations were significantly lower than measurements. A potential reason for some of these discrepancies involves interferences associated with the measurement of OH using the Laser-Induced Fluorescence – Fluorescence Assay with Gas Expansion (LIF-FAGE) technique in these environments. In this study, a turbulent flow reactor operating at atmospheric pressure was coupled to a LIF-FAGE cell and the OH signal produced from the ozonolysis of several BVOCs was measured. To distinguish between OH produced from the ozonolysis reactions and any OH artefact produced inside the LIF-FAGE cell, an external chemical scrubbing technique was used, allowing for the direct measurement of any interference. An interference under high ozone and BVOC concentrations was observed that was not laser generated and was independent of the ozonolysis reaction time. Addition of acetic acid to the reactor eliminated the interference, suggesting that the source of the interference in these experiments involved the decomposition of stabilized Criegee intermediates inside the FAGE detection cell.

scholarly journals Effect of isoprene emissions from major forests on ozone formation in the city of Shanghai, China

2011 ◽  
Vol 11 (6) ◽  
pp. 18527-18556 ◽  
Author(s):  
F. Geng ◽  
X. Tie ◽  
A. Guenther ◽  
G. Li ◽  
J. Cao ◽  
...  
Keyword(s):  
Ozone Production ◽  
Ozone Formation ◽  
Emission Model ◽  
Peroxy Radicals ◽  
Forest Regions ◽  
High Concentrations ◽  
The Impact ◽  
The City ◽  
Continuous Oxidation ◽  
Ho2 Radical

Abstract. Ambient surface level concentrations of isoprene (C5H8) were measured in the major forest regions located south of Shanghai, China. Because there is a large coverage of broad-leaved trees in this region, high concentrations of isoprene were measured, ranging from 1 to 6 ppbv. A regional dynamical/chemical model (WRF-Chem) is applied for studying the effect of such high concentrations of isoprene on the ozone production in the city of Shanghai. The evaluation of the model shows that the calculated isoprene concentrations agree with the measured concentrations when the measured isoprene concentrations are lower than 3 ppb, but underestimate the measurements when the measured values are higher than 3 ppb. Isoprene was underestimated only at sampling sites near large bamboo plantations, a high isoprene source, indicating the need to include geospatially resolved bamboo distributions in the biogenic emission model. The assessment of the impact of isoprene on ozone formation suggests that the concentrations of peroxy radicals (RO2) are significantly enhanced due to the oxidation of isoprene, with a maximum of 30 ppt. However, the enhancement of RO2 is confined to the forested regions. Because the concentrations of NOx were low in the forest regions, the ozone production due to the oxidation of isoprene (C5H8 + OH →→ RO2 + NO →→ O3) is low (less than 2–3 ppb/h). The calculation further suggests that the oxidation of isoprene leads to the enhancement of carbonyls (such as formaldehyde and acetaldehyde) in the regions downwind of the forests, due to continuous oxidation of isoprene in the forest air. As a result, the concentrations of HO2 radical are enhanced, resulting from the photo-disassociation of formaldehyde and acetaldehyde. Because the enhancement of HO2 radical occurs in regions downwind of the forests, the enhancement of ozone production (6–8 ppb/h) is higher than in the forest region, causing by higher anthropogenic emissions of NOx. This study suggests that the biogenic emissions in the major forests to the south of Shanghai have important impacts on the levels of ozone in the city, mainly due to the carbonyls produced by the continuous oxidation of isoprene in the forest air.

scholarly journals The impact of biogenic VOC emissions on photochemical ozone formation during a high ozone pollution episode in the Iberian Peninsula in the 2003 summer season

2008 ◽  
Vol 2 (1) ◽  
pp. 9-15 ◽  
Author(s):  
N. Castell ◽  
A. F. Stein ◽  
R. Salvador ◽  
E. Mantilla ◽  
M. Millán
Keyword(s):  
Organic Compound ◽  
Iberian Peninsula ◽  
Volatile Organic Compound ◽  
Biogenic Emissions ◽  
Ozone Formation ◽  
Ozone Pollution ◽  
Voc Emissions ◽  
Volatile Organic ◽  
Big Cities ◽  
The Impact

Abstract. Throughout Europe the summer of 2003 was exceptionally warm, especially July and August. The European Environment Agency (EEA) reported several ozone episodes, mainly in the first half of August. These episodes were exceptionally long-lasting, spatially extensive, and associated to high temperatures. In this paper, the 10$ndash;15 August 2003 ozone pollution event has been analyzed using meteorological and regional air quality modelling. During this period the threshold values of the European Directive 2002/3/EC were exceeded in various areas of the Iberian Peninsula. The aim of this paper is to computationally understand and quantify the influence of biogenic volatile organic compound (BVOC) emissions in the formation of tropospheric ozone during this high ozone episode. Being able to differentiate how much ozone comes from biogenic emissions alone and how much comes from the interaction between anthropogenic and biogenic emissions would be helpful to develop a feasible and effective ozone control strategy. The impact on ozone formation was also studied in combination with various anthropogenic emission reduction strategies, i.e., when anthropogenic VOC emissions and/or NOx emissions are reduced. The results show a great dependency of the BVOC contribution to ozone formation on the antropoghenic reduction scenario. In rural areas, the impact due to a NOx and/or VOC reduction does not change the BVOC impact. Nevertheless, within big cities or industrial zones, a NOx reduction results in a decrease of the biogenic impact in ozone levels that can reach 85 μg/m3, whereas an Anthropogenic Volatile Organic Compound (AVOC) reduction results in a decrease of the BVOC contribution on ozone formation that varies from 0 to 30 μg/m3 with respect to the contribution at the same points in the 2003 base scenario. On the other hand, downwind of the big cities, a decrease in NOx produces a minor contribution of biogenic emissions and a decrease in AVOCs results in greater contributions of BVOCs to the formation of ozone.

scholarly journals Insights into hydroxyl measurements and atmospheric oxidation in a California forest

2012 ◽  
Vol 12 (17) ◽  
pp. 8009-8020 ◽  
Author(s):  
J. Mao ◽  
X. Ren ◽  
L. Zhang ◽  
D. M. Van Duin ◽  
R. C. Cohen ◽  
...  
Keyword(s):  
Organic Compounds ◽  
Traditional Method ◽  
Laser Induced Fluorescence ◽  
New Method ◽  
Biogenic Volatile Organic Compounds ◽  
Temperature Dependent ◽  
Volatile Organic ◽  
Penn State ◽  
Oxidation Chemistry ◽  
Gas Expansion

Abstract. The understanding of oxidation in forest atmospheres is being challenged by measurements of unexpectedly large amounts of hydroxyl (OH). A significant number of these OH measurements were made by laser-induced fluorescence in low-pressure detection chambers (called Fluorescence Assay with Gas Expansion (FAGE)) using the Penn State Ground-based Tropospheric Hydrogen Oxides Sensor (GTHOS). We deployed a new chemical removal method to measure OH in parallel with the traditional FAGE method in a California forest. The new method gives on average only 40–60% of the OH from the traditional method and this discrepancy is temperature dependent. Evidence indicates that the new method measures atmospheric OH while the traditional method is affected by internally generated OH, possibly from oxidation of biogenic volatile organic compounds. The improved agreement between OH measured by this new technique and modeled OH suggests that oxidation chemistry in at least one forest atmosphere is better understood than previously thought.

scholarly journals Measurements of a potential interference with laser-induced fluorescence measurements of ambient OH from the ozonolysis of biogenic alkenes

2018 ◽  
Vol 11 (1) ◽  
pp. 1-16 ◽  
Author(s):  
Pamela Rickly ◽  
Philip S. Stevens
Keyword(s):  
Flow Reactor ◽  
Laser Induced Fluorescence ◽  
Fluorescence Measurements ◽  
Criegee Intermediates ◽  
Volatile Organic ◽  
Forested Areas ◽  
Ambient Concentrations ◽  
Rigorous Test ◽  
Reactor Operating ◽  
Gas Expansion

Abstract. Reactions of the hydroxyl radical (OH) play a central role in the chemistry of the atmosphere, and measurements of its concentration can provide a rigorous test of our understanding of atmospheric oxidation. Several recent studies have shown large discrepancies between measured and modeled OH concentrations in forested areas impacted by emissions of biogenic volatile organic compounds (BVOCs), where modeled concentrations were significantly lower than measurements. A potential reason for some of these discrepancies involves interferences associated with the measurement of OH using the laser-induced fluorescence–fluorescence assay by gas expansion (LIF-FAGE) technique in these environments. In this study, a turbulent flow reactor operating at atmospheric pressure was coupled to a LIF-FAGE cell and the OH signal produced from the ozonolysis of α-pinene, β-pinene, ocimene, isoprene, and 2-methyl-3-buten-2-ol (MBO) was measured. To distinguish between OH produced from the ozonolysis reactions and any OH artifact produced inside the LIF-FAGE cell, an external chemical scrubbing technique was used, allowing for the direct measurement of any interference. An interference under high ozone (between 2 × 1013 and 10 × 1013 cm−3) and BVOC concentrations (between approximately 0.1 × 1012 and 40 × 1012 cm−3) was observed that was not laser generated and was independent of the ozonolysis reaction time. For the ozonolysis of α- and β-pinene, the observed interference accounted for approximately 40 % of the total OH signal, while for the ozonolysis of ocimene the observed interference accounted for approximately 70 % of the total OH signal. Addition of acetic acid to the reactor eliminated the interference, suggesting that the source of the interference in these experiments involved the decomposition of stabilized Criegee intermediates (SCIs) inside the FAGE detection cell. Extrapolation of these measurements to ambient concentrations suggests that these interferences should be below the detection limit of the instrument.

scholarly journals Effect of isoprene emissions from major forests on ozone formation in the city of Shanghai, China

2011 ◽  
Vol 11 (20) ◽  
pp. 10449-10459 ◽  
Author(s):  
F. Geng ◽  
X. Tie ◽  
A. Guenther ◽  
G. Li ◽  
J. Cao ◽  
...  
Keyword(s):  
Ozone Production ◽  
Ozone Formation ◽  
Emission Model ◽  
Peroxy Radicals ◽  
Forest Regions ◽  
High Concentrations ◽  
The Impact ◽  
The City ◽  
Continuous Oxidation ◽  
Ho2 Radical

Abstract. Ambient surface level concentrations of isoprene (C5H8) were measured in the major forest regions located south of Shanghai, China. Because there is a large coverage of broad-leaved trees in this region, high concentrations of isoprene were measured, ranging from 1 to 6 ppbv. A regional dynamical/chemical model (WRF-Chem) is applied for studying the effect of such high concentrations of isoprene on the ozone production in the city of Shanghai. The evaluation of the model shows that the calculated isoprene concentrations agree with the measured concentrations when the measured isoprene concentrations are lower than 3 ppb, but underestimate the measurements when the measured values are higher than 3 ppb. Isoprene was underestimated only at sampling sites near large bamboo plantations, a high isoprene source, indicating the need to include geospatially resolved bamboo distributions in the biogenic emission model. The assessment of the impact of isoprene on ozone formation suggests that the concentrations of peroxy radicals (RO2) are significantly enhanced due to the oxidation of isoprene, with a maximum of 30 ppt. However, the enhancement of RO2 is confined to the forested regions. Because the concentrations of NOx were low in the forest regions, the ozone production due to the oxidation of isoprene (C5H8 + OH → → RO2 + NO → → O3) is low (less than 2–3 ppb h−1). The calculation further suggests that the oxidation of isoprene leads to the enhancement of carbonyls (such as formaldehyde and acetaldehyde) in the regions downwind of the forests, due to continuous oxidation of isoprene in the forest air. As a result, the concentrations of HO2 radical are enhanced, resulting from the photo-disassociation of formaldehyde and acetaldehyde. Because the enhancement of HO2 radical occurs in regions downwind of the forests, the enhancement of ozone production (6–8 ppb h−1) is higher than in the forest region, causing by higher anthropogenic emissions of NOx. This study suggests that the biogenic emissions in the major forests to the south of Shanghai have important impacts on the levels of ozone in the city, mainly due to the carbonyls produced by the continuous oxidation of isoprene in the forest air.

Chamber Studies of NO3 reactivity during the oxidation of isoprene

2020 ◽  
Author(s):  
Patrick Dewald ◽  
Justin Shenolikar ◽  
Nils Friedrich ◽  
Franz Rohrer ◽  
Ralf Tillmann ◽  
...  
Keyword(s):  
Oxidation Products ◽  
Research Centre ◽  
Biogenic Emissions ◽  
Organic Nitrates ◽  
Peroxy Radicals ◽  
Experimental Conditions ◽  
Mixing Ratios ◽  
Volatile Organic ◽  
Isoprene Oxidation ◽  
Chamber Studies

<p>Isoprene is the major volatile organic compound that is released into the environment via biogenic emissions and its oxidation can result in formation of secondary organic aerosol (SOA). Although isoprene emission occurs mainly at daytime, it can accumulate at nighttime and be oxidized by the nitrate radical (NO<sub>3</sub>) to form organic nitrates that can partition to the particle phase. A detailed understanding of the reaction between isoprene and NO<sub>3</sub> is thus required to predict its role in e.g. NO<sub>X</sub> lifetimes and SOA formation.</p><p>The reaction between NO<sub>3</sub> and isoprene was investigated under varying experimental conditions (high or low RO<sub>2</sub>/HO<sub>2</sub>, temperature, humidity, seed aerosols) during the NO3ISOP campaign at the atmospheric simulation chamber SAPHIR of the research centre in Jülich (Germany). Direct measurement of the NO<sub>3</sub> reactivity was carried out with means of a flowtube coupled to a cavity-ring-down spectroscopy (FT-CRDS) setup which enabled the evolution of the NO<sub>3</sub> lifetime during the isoprene oxidation process to be monitored.</p><p>By comparing direct NO<sub>3</sub> reactivity measurements with those calculated from VOC mixing ratios and those calculated from a stationary-state analysis we identify the contributions of isoprene, secondary oxidation products and peroxy radicals to NO<sub>3</sub> losses.</p>

scholarly journals Insights into hydroxyl measurements and atmospheric oxidation in a California forest

2012 ◽  
Vol 12 (3) ◽  
pp. 6715-6744 ◽  
Author(s):  
J. Mao ◽  
X. Ren ◽  
W. H. Brune ◽  
D. M. Van Duin ◽  
R. C. Cohen ◽  
...  
Keyword(s):  
Organic Compounds ◽  
Traditional Method ◽  
Laser Induced Fluorescence ◽  
New Method ◽  
Biogenic Volatile Organic Compounds ◽  
Temperature Dependent ◽  
Volatile Organic ◽  
Penn State ◽  
Oxidation Chemistry ◽  
Gas Expansion

Abstract. The understanding of oxidation in forest atmospheres is being challenged by measurements of unexpectedly large amounts of hydroxyl (OH). A significant number of these OH measurements were made by laser-induced fluorescence in low-pressure detection chambers (called Fluorescence Assay with Gas Expansion (FAGE)) using the Penn State Ground-based Tropospheric Hydrogen Oxides Sensor (GTHOS). We deployed a new chemical removal method to measure OH in parallel with the traditional FAGE method. The new method gives on average only 40–50% of the OH from the traditional method and this discrepancy is temperature-dependent. Evidence indicates that the new method measures atmospheric OH while the traditional method is affected by internally generated OH, possibly from oxidation of biogenic volatile organic compounds. The agreement between OH measured by this new technique and modeled OH suggests that oxidation chemistry in at least one forest atmosphere is better understood than previously thought.

scholarly journals Hohenpeissenberg Photochemical Experiment (HOPE 2000): Measurements and photostationary state calculations of OH and peroxy radicals

2003 ◽  
Vol 3 (5) ◽  
pp. 1565-1588 ◽  
Author(s):  
G. M. Handisides ◽  
C. Plass-Dülmer ◽  
S. Gilge ◽  
H. Bingemer ◽  
H. Berresheim
Keyword(s):  
Peroxy Radical ◽  
Balance Model ◽  
Peroxy Radicals ◽  
Mixing Ratios ◽  
Photostationary State ◽  
Meteorological Observatory ◽  
Volatile Organic ◽  
The Impact ◽  
Made In ◽  
Measurement Period

Abstract. Measurements of OH, total peroxy radicals, non-methane hydrocarbons (NMHCs) and various other trace gases were made at the Meteorological Observatory Hohenpeissenberg in June 2000. The data from an intensive measurement period characterised by high solar insolation (18-21 June) are analysed. The maximum midday OH concentration ranged between 4.5x106 molecules cm-3 and 7.4x106 molecules cm-3. The maximum total ROx (ROx =OH+RO+HO2+RO2) mixing ratio increased from about 55 pptv on 18 June to nearly 70 pptv on 20 and 21 June. A total of 64 NMHCs, including isoprene and monoterpenes, were measured every 1 to 6 hours. The oxidation rate of the NMHCs by OH was calculated and reached a total of over 14x106 molecules cm-3 s-1 on two days. A simple photostationary state balance model was used to simulate the ambient OH and peroxy radical concentrations with the measured data as input. This approach was able to reproduce the main features of the diurnal profiles of both OH and peroxy radicals. The balance equations were used to test the effect of the assumptions made in this model. The results proved to be most sensitive to assumptions about the impact of unmeasured volatile organic compounds (VOC), e.g. formaldehyde (HCHO), and about the partitioning between HO2 and RO2. The measured OH concentration and peroxy radical mixing ratios were reproduced well by assuming the presence of 3 ppbv HCHO as a proxy for oxygenated hydrocarbons, and a HO2/ RO2 ratio between 1:1 and 1:2. The most important source of OH, and conversely the greatest sink for peroxy radicals, was the recycling of HO2 radicals to OH. This reaction was responsible for the recycling of more than 45x106 molecules cm-3 s-1 on two days. The most important sink for OH, and the largest source of peroxy radicals, was the oxidation of NMHCs, in particular, of isoprene and the monoterpenes.

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