Comparison of OH reactivity measurements in the atmospheric simulation chamber SAPHIR

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 were used 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 vapour, nitrogen oxides, various organic compounds) by all instruments. The precision of the measurements (limit of detection  < 1 s−1 at a time resolution of 30 s to a few minutes) is higher for instruments directly detecting hydroxyl radicals, whereas the indirect comparative reactivity method (CRM) has a higher limit of detection of 2 s−1 at a time resolution of 10 to 15 min. The performances of the instruments were systematically tested by stepwise increasing, for example, the concentrations of carbon monoxide (CO), water vapour or nitric oxide (NO). In further experiments, mixtures of organic reactants were injected into the chamber to simulate urban and forested environments. Overall, the results show that the instruments are capable of measuring OH reactivity in the presence of CO, alkanes, alkenes and aromatic compounds. The transmission efficiency in Teflon inlet lines could have introduced systematic errors in measurements for low-volatile organic compounds in some instruments. CRM instruments exhibited a larger scatter in the data compared to the other instruments. The largest differences to reference measurements or to calculated reactivity were observed by CRM instruments in the presence of terpenes and oxygenated organic compounds (mixing ratio of OH reactants were up to 10 ppbv). In some of these experiments, only a small fraction of the reactivity is detected. The accuracy of CRM measurements is most likely limited by the corrections that need to be applied to account for known effects of, for example, deviations from pseudo first-order conditions, nitrogen oxides or water vapour on the measurement. Methods used to derive these corrections vary among the different CRM instruments. Measurements taken with a flow-tube instrument combined with the direct detection of OH by chemical ionisation mass spectrometry (CIMS) show limitations in cases of high reactivity and high NO concentrations but were accurate for low reactivity (< 15 s−1) and low NO (< 5 ppbv) conditions.

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Effects of gas–wall interactions on measurements of semivolatile compounds and small polar molecules

Atmospheric Measurement Techniques ◽

10.5194/amt-12-3137-2019 ◽

2019 ◽

Vol 12 (6) ◽

pp. 3137-3149 ◽

Cited By ~ 12

Author(s):

Xiaoxi Liu ◽

Benjamin Deming ◽

Demetrios Pagonis ◽

Douglas A. Day ◽

Brett B. Palm ◽

...

Keyword(s):

Organic Compounds ◽

Transmission Efficiency ◽

Polar Molecules ◽

Ionization Mass ◽

Atmospheric Measurements ◽

Wide Range ◽

Teflon Tubing ◽

Gas Interactions

Abstract. Recent work has quantified the delay times in measurements of volatile organic compounds (VOCs) caused by the partitioning between the gas phase and the surfaces of the inlet tubing and instrument itself. In this study we quantify wall partitioning effects on time responses and transmission of multifunctional, semivolatile, and intermediate-volatility organic compounds (S/IVOCs) with saturation concentrations (C∗) between 100 and 104 µg m−3. The instrument delays of several chemical ionization mass spectrometer (CIMS) instruments increase with decreasing C∗, ranging from seconds to tens of minutes, except for the NO3- CIMS where it is always on the order of seconds. Six different tubing materials were tested. Teflon, including PFA, FEP, and conductive PFA, performs better than metals and Nafion in terms of both delay time and transmission efficiency. Analogous to instrument responses, tubing delays increase as C∗ decreases, from less than a minute to >100 min. The delays caused by Teflon tubing vs. C∗ can be modeled using the simple chromatography model of Pagonis et al. (2017). The model can be used to estimate the equivalent absorbing mass concentration (Cw) of each material, and to estimate delays under different flow rates and tubing dimensions. We also include time delay measurements from a series of small polar organic and inorganic analytes in PFA tubing measured by CIMS. Small polar molecules behave differently than larger organic ones, with their delays being predicted by their Henry's law constants instead of their C∗, suggesting the dominance of partitioning to small amounts of water on sampling surfaces as a result of their polarity and acidity properties. PFA tubing has the best performance for gas-only sampling, while conductive PFA appears very promising for sampling S/IVOCs and particles simultaneously. The observed delays and low transmission both affect the quality of gas quantification, especially when no direct calibration is available. Improvements in sampling and instrument response are needed for fast atmospheric measurements of a wide range of S/IVOCs (e.g., by aircraft or for eddy covariance). These methods and results are also useful for more general characterization of surface–gas interactions.

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New insights into secondary organic aerosol from nitrate oxidation of isoprene in the atmospheric simulation chamber SAPHIR

10.5194/egusphere-egu2020-11986 ◽

2020 ◽

Author(s):

Juliane L. Fry ◽

Bellamy Brownwood ◽

Thorsten Hohaus ◽

Avtandil Turdziladze ◽

Philip Carlsson ◽

...

Keyword(s):

Secondary Organic Aerosol ◽

Organic Aerosol ◽

Organic Nitrate ◽

Nitrate Radical ◽

Peroxy Radicals ◽

Radical Reactivity ◽

No3 Radical ◽

Chemical Conditions ◽

Seed Aerosol ◽

Simulation Chamber

Experiments at a set of atmospherically relevant conditions were performed in the atmospheric simulation chamber SAPHIR, investigating the oxidation of isoprene by the nitrate radical (NO3). A comprehensive set of instruments detected trace gases, radicals, aerosol properties and hydroxyl (OH) and NO3 radical reactivity. The chemical conditions in the chamber were varied to change the fate of the peroxy radicals (RO2) formed after the reaction between NO3 and isoprene, and seed aerosol of varying composition was added to initiate gas/aerosol partitioning. This presentation discusses observed gas/aerosol partitioning of the major organic nitrate products and summarizes the observations of secondary organic aerosol yield.

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Effects of Gas-Wall Interactions on Measurements of Semivolatile Compounds and Small Polar Molecules

10.5194/amt-2019-52 ◽

2019 ◽

Cited By ~ 2

Author(s):

Xiaoxi Liu ◽

Benjamin Deming ◽

Demetrios Pagonis ◽

Douglas A. Day ◽

Brett B. Palm ◽

...

Keyword(s):

Organic Compounds ◽

Transmission Efficiency ◽

Polar Molecules ◽

Ionization Mass ◽

Atmospheric Measurements ◽

Wide Range ◽

Teflon Tubing ◽

Gas Interactions

Abstract. Recent work has quantified the delay times in measurements of volatile organic compounds (VOCs) caused by the partitioning between the gas phase and the surfaces of the inlet tubing and instrument itself. In this study we quantify wall partitioning effects on time responses and transmission of multi-functional, semivolatile and intermediate-volatility organic compounds (S/IVOCs) with saturation concentrations (C*) between 100 and 104 µg m−3. The instrument delays of several chemical ionization mass spectrometer (CIMS) instruments increase with decreasing C*, ranging from seconds to tens of minutes, except for the NO3−-CIMS where it is always on the order of seconds. Six different tubing materials were tested. Teflon, including PFA, FEP, and conductive PFA, performs better than metals and Nafion in terms of both delay time and transmission efficiency. Analogous to instrument responses, tubing delays increase as C* decreases, from less than a minute to > 100 min. The delays caused by Teflon tubing vs. C* can be modeled using the simple chromatography model of Pagonis et al. (2017). The model can be used to estimate the equivalent absorbing mass concentration (Cw) of each material, and to estimate delays under different flow rates and tubing dimensions. We also include time delay measurements from a series of small polar organic and inorganic analytes in PFA tubing measured by CIMS. Small polar molecules behave differently than larger organic ones, with their delays being predicted by their Henry’s law constants instead of their C*, suggesting the dominance of partitioning to small amounts of water on sampling surfaces as a result of their polarity and acidity properties. PFA tubing has the best performance for gas-only sampling, while conductive PFA appears very promising for sampling S/IVOCs and particles simultaneously. The observed delays and low transmission both affect the quality of gas quantification, especially when no direct calibration is available. Improvements in sampling and instrument response are needed for fast atmospheric measurements of a wide range of S/IVOCs (e.g., by aircraft or for eddy covariance). These methods and results are also useful for more general characterization of surface/gas interactions.

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Importance of isomerization reactions for the OH radical regeneration from the photo-oxidation of isoprene investigated in the atmospheric simulation chamber SAPHIR

10.5194/egusphere-egu2020-5475 ◽

2020 ◽

Author(s):

Anna Novelli ◽

Luc Vereecken ◽

Birger Bohn ◽

Hans-Peter Dorn ◽

Georgios Gkatzelis ◽

...

Keyword(s):

Oh Radicals ◽

Oh Radical ◽

Peroxy Radicals ◽

Atmospheric Conditions ◽

Unimolecular Reactions ◽

Model Calculations ◽

Hydrogen Shift ◽

Wide Range ◽

Regeneration Efficiency ◽

Simulation Chamber

Theoretical, laboratory and chamber studies have shown fast regeneration of hydroxyl radical (OH) in the photochemistry of isoprene largely due to previously disregarded unimolecular reactions which were previously thought not to be important under atmospheric conditions. Based on early field measurements, nearly complete regeneration was hypothesized for a wide range of tropospheric conditions, including areas such as the rainforest where slow regeneration of OH radicals is expected due to low concentrations of nitric oxide (NO). In this work the OH regeneration in the isoprene oxidation is directly quantified for the first time through experiments covering a wide range of atmospheric conditions (i.e. NO between 0.15 and 2 ppbv and temperature between 25 and 41&#176;C) in the atmospheric simulation chamber SAPHIR. These conditions cover remote areas partially influenced by anthropogenic NO emissions, giving a regeneration efficiency of OH close to one, and areas like the Amazonian rainforest with very low NO, resulting in a surprisingly high regeneration efficiency of 0.5, i.e. a factor of 2 to 3 higher than explainable in the absence of unimolecular reactions. The measured radical concentrations were compared to model calculations and the best agreement was observed when at least 50% of the total loss of isoprene peroxy radicals conformers (weighted by their abundance) occurs via isomerization reactions for NO lower than 0.2 parts per billion (ppbv). For these levels of NO, up to 50% of the OH radicals are regenerated from the products of the 1,6 &#945;-hydroxy-hydrogen shift (1,6-H shift) of Z-&#948;-RO2 radicals through photolysis of an unsaturated hydroperoxy aldehyde (HPALD) and/or through the fast aldehyde hydrogen shift (rate constant ~10 s-1 at 300K) in di-hydroperoxy carbonyl peroxy radicals (di-HPCARP-RO2), depending on their relative yield. The agreement between all measured and modelled trace gases (hydroxyl, hydroperoxy and organic peroxy radicals, carbon monoxide and the sum of methyl vinyl ketone, methacrolein and hydroxyl hydroperoxides) is nearly independent on the adopted yield of HPALD and di-HPCARP-RO2 as both degrade relatively fast (< 1 h), forming OH radical and CO among other products. Taking into consideration this and earlier isoprene studies, considerable uncertainties remain on the oxygenated products distribution, which affect radical levels and organic aerosol downwind of unpolluted isoprene dominated regions.

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Global warming potential estimates for the C1–C3 hydrochlorofluorocarbons (HCFCs) included in the Kigali Amendment to the Montreal Protocol

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-6317-2018 ◽

2018 ◽

Vol 18 (9) ◽

pp. 6317-6330 ◽

Cited By ~ 13

Author(s):

Dimitrios K. Papanastasiou ◽

Allison Beltrone ◽

Paul Marshall ◽

James B. Burkholder

Keyword(s):

Global Warming ◽

Montreal Protocol ◽

Oh Radical ◽

Radical Reactivity ◽

Structure Activity ◽

Wide Range ◽

Infrared Absorption Spectra ◽

Global Warming Potentials ◽

Ozone Depleting Substances ◽

The Individual

Abstract. Hydrochlorofluorocarbons (HCFCs) are ozone depleting substances and potent greenhouse gases that are controlled under the Montreal Protocol. However, the majority of the 274 HCFCs included in Annex C of the protocol do not have reported global warming potentials (GWPs) which are used to guide the phaseout of HCFCs and the future phase down of hydrofluorocarbons (HFCs). In this study, GWPs for all C1–C3 HCFCs included in Annex C are reported based on estimated atmospheric lifetimes and theoretical methods used to calculate infrared absorption spectra. Atmospheric lifetimes were estimated from a structure activity relationship (SAR) for OH radical reactivity and estimated O(1D) reactivity and UV photolysis loss processes. The C1–C3 HCFCs display a wide range of lifetimes (0.3 to 62 years) and GWPs (5 to 5330, 100-year time horizon) dependent on their molecular structure and the H-atom content of the individual HCFC. The results from this study provide estimated policy-relevant GWP metrics for the HCFCs included in the Montreal Protocol in the absence of experimentally derived metrics.

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The AquaVIT-1 intercomparison of atmospheric water vapor measurement techniques

Atmospheric Measurement Techniques ◽

10.5194/amt-7-3177-2014 ◽

2014 ◽

Vol 7 (9) ◽

pp. 3177-3213 ◽

Cited By ~ 58

Author(s):

D. W. Fahey ◽

R.-S. Gao ◽

O. Möhler ◽

H. Saathoff ◽

C. Schiller ◽

...

Keyword(s):

Water Vapor ◽

Measurement Techniques ◽

Reference Value ◽

Atmospheric Water Vapor ◽

Mixing Ratio ◽

Atmospheric Water ◽

Atmospheric Measurements ◽

Core Subset ◽

Moving Platforms ◽

Chamber Volume

Abstract. The AquaVIT-1 intercomparison of atmospheric water vapor measurement techniques was conducted at the aerosol and cloud simulation chamber AIDA (Aerosol Interaction and Dynamics in the Atmosphere) at the Karlsruhe Institute of Technology, Germany, in October 2007. The overall objective was to intercompare state-of-the-art and prototype atmospheric hygrometers with each other and with independent humidity standards under controlled conditions. This activity was conducted as a blind intercomparison with coordination by selected referees. The effort was motivated by persistent discrepancies found in atmospheric measurements involving multiple instruments operating on research aircraft and balloon platforms, particularly in the upper troposphere and lower stratosphere, where water vapor reaches its lowest atmospheric values (less than 10 ppm). With the AIDA chamber volume of 84 m3, multiple instruments analyzed air with a common water vapor mixing ratio, by extracting air into instrument flow systems, by locating instruments inside the chamber, or by sampling the chamber volume optically. The intercomparison was successfully conducted over 10 days during which pressure, temperature, and mixing ratio were systematically varied (50 to 500 hPa, 185 to 243 K, and 0.3 to 152 ppm). In the absence of an accepted reference instrument, the absolute accuracy of the instruments was not established. To evaluate the intercomparison, the reference value was taken to be the ensemble mean of a core subset of the measurements. For these core instruments, the agreement between 10 and 150 ppm of water vapor is considered good with variation about the reference value of about ±10% (±1σ). In the region of most interest between 1 and 10 ppm, the core subset agreement is fair with variation about the reference value of ±20% (±1σ). The upper limit of precision was also derived for each instrument from the reported data. The implication for atmospheric measurements is that the substantially larger differences observed during in-flight intercomparisons stem from other factors associated with the moving platforms or the non-laboratory environment. The success of AquaVIT-1 provides a template for future intercomparison efforts with water vapor or other species that are focused on improving the analytical quality of atmospheric measurements on moving platforms.

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The AquaVIT-1 intercomparison of atmospheric water vapor measurement techniques

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-7-3159-2014 ◽

2014 ◽

Vol 7 (4) ◽

pp. 3159-3251 ◽

Cited By ~ 13

Author(s):

D. W. Fahey ◽

R.-S. Gao ◽

O. Möhler ◽

H. Saathoff ◽

C. Schiller ◽

...

Keyword(s):

Water Vapor ◽

Measurement Techniques ◽

Reference Value ◽

Mixing Ratio ◽

Atmospheric Water ◽

Atmospheric Measurements ◽

The Core ◽

Core Subset ◽

Moving Platforms ◽

Chamber Volume

Abstract. The AquaVIT-1 Intercomparison of Atmospheric Water Vapor Measurement Techniques was conducted at the aerosol and cloud simulation chamber AIDA at the Karlsruhe Institute of Technology, Germany, in October 2007. The overall objective was to intercompare state-of-the-art and prototype atmospheric hygrometers with each other and with independent humidity standards under controlled conditions. This activity was conducted as a blind intercomparison with coordination by selected referees. The effort was motivated by persistent discrepancies found in atmospheric measurements involving multiple instruments operating on research aircraft and balloon platforms, particularly in the upper troposphere and lower stratosphere where water vapor reaches its lowest atmospheric values (less than 10 ppm). With the AIDA chamber volume of 84 m3, multiple instruments analyzed air with a common water vapor mixing ratio, either by extracting air into instrument flow systems, locating instruments inside the chamber, or sampling the chamber volume optically. The intercomparison was successfully conducted over 10 days during which pressure, temperature, and mixing ratio were systematically varied (50 to 500 hPa, 185 to 243 K, and 0.3 to 152 ppm). In the absence of an accepted reference instrument, the reference value was taken to be the ensemble mean of a core subset of the measurements. For these core instruments, the agreement between 10 and 150 ppm of water vapor is considered good with variation about the reference value of about ±10% (±1σ). In the region of most interest between 1 and 10 ppm, the core subset agreement is fair with variation about the reference value of ±20% (±1σ). The upper limit of precision was also derived for each instrument from the reported data. These results indicate that the core instruments, in general, have intrinsic skill to determine unknown water vapor mixing ratios with an accuracy of at least ±20%. The implication for atmospheric measurements is that the substantially larger differences observed during in-flight intercomparisons stem from other factors associated with the moving platforms or the non-laboratory environment. The success of AquaVIT-1 provides a template for future intercomparison efforts with water vapor or other species that are focused on improving the analytical quality of atmospheric measurements on moving platforms.

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Global Warming Potentials for the C1-C3 Hydrochlorofluorocarbons (HCFCs) Included in the Kigali Amendment to the Montreal Protocol

10.5194/acp-2018-27 ◽

2018 ◽

Cited By ~ 1

Author(s):

Dimitrios K. Papanastasiou ◽

Allison Beltrone ◽

Paul Marshall ◽

James B. Burkholder

Keyword(s):

Global Warming ◽

Montreal Protocol ◽

Oh Radical ◽

Radical Reactivity ◽

Structure Activity ◽

Wide Range ◽

Global Warming Potentials ◽

Ozone Depleting Substances ◽

The Individual ◽

Phase Out

Abstract. Hydrochlorofluorocarbons (HCFCs) are ozone depleting substances and potent greenhouse gases that are controlled under the Montreal Protocol. However, the majority of the 274 HCFCs included in Annex C of the protocol do not have reported global warming potentials (GWPs) that are used to guide the phase-out of HCFCs and the future phase-down of hydrofluorocarbons (HFCs). In this study, GWPs for all C1-C3 HCFCs included in Annex C are reported based on estimated atmospheric lifetimes and theoretical methods used to calculate infrared absorption spectra. Atmospheric lifetimes were estimated from a structure activity relationship (SAR) for OH radical reactivity and estimated O(1D) reactivity and UV photolysis loss processes. The HCFCs display a wide range of lifetimes and GWPs dependent on their molecular structure and H-atom content of the individual HCFC. The results from this study provide reliable policy relevant GWP metrics for the HCFCs included in the Montreal Protocol in the absence of experimentally derived metrics.

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Origin and variability in volatile organic compounds observed at an Eastern Mediterranean background site (Cyprus)

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-11355-2017 ◽

2017 ◽

Vol 17 (18) ◽

pp. 11355-11388 ◽

Cited By ~ 17

Author(s):

Cécile Debevec ◽

Stéphane Sauvage ◽

Valérie Gros ◽

Jean Sciare ◽

Michael Pikridas ◽

...

Keyword(s):

Volatile Organic Compounds ◽

Organic Compounds ◽

Eastern Mediterranean ◽

Atmospheric Measurements ◽

Air Masses ◽

Background Site ◽

Regional Background ◽

Local Origin ◽

Wide Range ◽

Volatile Organic

Abstract. More than 7000 atmospheric measurements of over 60 C2 − C16 volatile organic compounds (VOCs) were conducted at a background site in Cyprus during a 1-month intensive field campaign held in March 2015. This exhaustive dataset consisted of primary anthropogenic and biogenic VOCs, including a wide range of source-specific tracers, and oxygenated VOCs (with various origins) that were measured online by flame ionization detection–gas chromatography and proton transfer mass spectrometry. Online submicron aerosol chemical composition was performed in parallel using an aerosol mass spectrometer. This study presents the high temporal variability in VOCs and their associated sources. A preliminary analysis of their time series was performed on the basis of independent tracers (NO, CO, black carbon), meteorological data and the clustering of air mass trajectories. Biogenic compounds were mainly attributed to a local origin and showed compound-specific diurnal cycles such as a daily maximum for isoprene and a nighttime maximum for monoterpenes. Anthropogenic VOCs as well as oxygenated VOCs displayed higher mixing ratios under the influence of continental air masses (i.e., western Asia), indicating that long-range transport significantly contributed to the VOC levels in the area. Source apportionment was then conducted on a database of 20 VOCs (or grouped VOCs) using a source receptor model. The positive matrix factorization and concentration field analyses were hence conducted to identify and characterize covariation factors of VOCs that were representative of primary emissions as well as chemical transformation processes. A six-factor PMF solution was selected, namely two primary biogenic factors (relative contribution of 43 % to the total mass of VOCs) for different types of emitting vegetation; three anthropogenic factors (short-lived combustion source, evaporative sources, industrial and evaporative sources; 21 % all together), identified as being either of local origin or from more distant emission zones (i.e., the south coast of Turkey); and a last factor (36 %) associated with regional background pollution (air masses transported both from the Western and Eastern Mediterranean regions). One of the two biogenic and the regional background factors were found to be the largest contributors to the VOC concentrations observed at our sampling site. Finally, a combined analysis of VOC PMF factors with source-apportioned organic aerosols (OAs) helped to better distinguish between anthropogenic and biogenic influences on the aerosol and gas phase compositions. The highest OA concentrations were observed when the site was influenced by air masses rich in semi-volatile OA (less oxidized aerosols) originating from the southwest of Asia, in contrast with OA factor contributions associated with the remaining source regions. A reinforcement of secondary OA formation also occurred due to the intense oxidation of biogenic precursors.

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Comparison of OH reactivity measurements in the atmospheric simulation chamber SAPHIR