Measurement report: Observation-based formaldehyde  production rates and their relation to OH reactivity around the Arabian Peninsula

Abstract. Formaldehyde (HCHO) is the most abundant aldehyde in the troposphere. While its background mixing ratio is mostly determined by the oxidation of methane, in many environments, especially in the boundary layer, HCHO can have a large variety of precursors, in particular biogenic and anthropogenic volatile organic compounds (VOCs) and their oxidation products. Here we present shipborne observations of HCHO, hydroxyl radical (OH) and OH reactivity (R(OH)), which were obtained during the Air Quality and Climate Change in the Arabian Basin (AQABA) campaign in summer 2017. The loss rate of HCHO was inferred from its reaction with OH, measured photolysis rates and dry deposition. In photochemical steady state, the HCHO loss is balanced by production via OH-initiated degradation of VOCs, photolysis of oxygenated VOCs (OVOCs) and the ozonolysis of alkenes. The slope αeff from a scatter plot of the HCHO production rate versus the product of OH and R(OH)eff (excluding inorganic contribution) yields the fraction of OH reactivity that contributes to HCHO production. Values of αeff varied between less than 2 % in relatively clean air over the Arabian Sea and the southern Red Sea and up to 32 % over the polluted Arabian Gulf (also known as Persian Gulf), signifying that polluted areas harbor a larger variety of HCHO precursors. The separation of R(OH)eff into individual compound classes revealed that elevated values of αeff coincided with increased contribution of alkanes and OVOCs, with the highest reactivity of all VOCs over the Arabian Gulf.

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Measurement report: Observation-based formaldehyde production rates and their relation to OH reactivity around the Arabian Peninsula

10.5194/acp-2021-304 ◽

2021 ◽

Author(s):

Dirk Dienhart ◽

John N. Crowley ◽

Efstratios Bourtsoukidis ◽

Achim Edtbauer ◽

Philipp G. Eger ◽

...

Keyword(s):

Volatile Organic Compounds ◽

Organic Compounds ◽

Arabian Gulf ◽

Oxidation Products ◽

Mixing Ratios ◽

Oxidation Of Methane ◽

Production Values ◽

Oxygenated Volatile Organic Compounds ◽

Volatile Organic ◽

The Persian Gulf

Abstract. Formaldehyde (HCHO) is the most abundant aldehyde in the troposphere. While its background-mixing ratio is mostly determined by the oxidation of methane, in many environments, especially in the boundary layer, HCHO can have a large variety of precursors, in particular biogenic and anthropogenic volatile organic compounds (VOCs) and their oxidation products. Here we present shipborne observations of HCHO, hydroxyl radical (OH) and OH reactivity (R(OH)), obtained during the Air Quality and Climate Change in the Arabian Basin (AQABA) campaign in summer 2017. The loss rate of HCHO was inferred from its reaction with OH, measured photolysis rates, and dry deposition. In photo-stationary state, the HCHO loss is balanced by production via OH initiated degradation of volatile organic compounds (VOCs), photolysis of oxygenated volatile organic compounds (OVOCs) and the ozonolysis of alkenes. The slope α from a scatter plot of the HCHO production rate versus the product of R(OH) and OH yields the fraction of R(OH) that contributes to HCHO production. Values of α varied between less than 2 % in rather clean air over the Arabian Sea and the southern Red Sea, and up to 32 % over the polluted Arabian Gulf (also known as the Persian Gulf), signifying that polluted areas harbour a larger variety of HCHO precursors. The HCHO yield from R(OH) depends on the absolute and relative contributions of alkanes, alkenes, oxygenated volatile organic compounds (OVOCs) and aromatics to R(OH), while no significant correlation to NOx mixing ratios was found, indicating that HCHO production was not NOx limited.

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Insights into the O : C dependent mechanisms controlling the evaporation of α-pinene secondary organic aerosol particles

10.5194/acp-2018-1305 ◽

2019 ◽

Author(s):

Angela Buchholz ◽

Andrew T. Lambe ◽

Arttu Ylisirniö ◽

Zijun Li ◽

Olli-Pekka Tikkanen ◽

...

Keyword(s):

Flow Reactor ◽

Secondary Organic Aerosol ◽

Organic Aerosol ◽

Oxidation Products ◽

Particle Phase ◽

Volatile Organic ◽

Isothermal Evaporation ◽

Key Factor ◽

Clean Air ◽

Measured Particle

Abstract. The volatility of oxidation products of volatile organic compounds (VOCs) in the atmosphere is a key factor to determine if they partition into the particle phase contributing to secondary organic aerosol (SOA) mass. Thus, linking volatility and measured particle composition will provide insights into SOA formation and its fate in the atmosphere. We produced a-pinene SOA with three different oxidation levels (characterised by average oxygen to carbon ratio, O : C = 0.53, 0.69, and 0.96) in an oxidation flow reactor. We investigated the particle volatility by isothermal evaporation in clean air as a function of relative humidity (RH

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Correcting Bias in Log-Linear Instrument Calibrations in the Context of Chemical Ionization Mass Spectrometry

10.5194/amt-2021-149 ◽

2021 ◽

Author(s):

Chenyang Bi ◽

Jordan E. Krechmer ◽

Manjula R. Canagaratna ◽

Gabriel Isaacman-VanWertz

Keyword(s):

Chemical Ionization ◽

Correction Method ◽

Operating Conditions ◽

Oxidation Products ◽

Mathematical Work ◽

Ionization Mass ◽

Individual Compound ◽

Linear Calibration ◽

Order Of Magnitude ◽

Log Linear

Abstract. Quantitative calibration of analytes using chemical ionization mass spectrometers (CIMS) has been hindered by the lack of commercially available standards of atmospheric oxidation products. To accurately calibrate analytes without standards, techniques have been recently developed to log-linearly correlate analyte sensitivity with instrument operating conditions. However, there is an inherent bias when applying log-linear calibration relationships that is typically ignored. In this study, we examine the bias in a log-linear based calibration curve based on prior mathematical work. We quantify the potential bias within the context of a CIMS-relevant relationship between analyte sensitivity and instrument voltage differentials. Uncertainty in three parameters has the potential to contribute to the bias, specifically the inherent extent to which the nominal relationship can capture true sensitivity, the slope of the relationship, and the voltage differential below which maximum sensitivity is achieved. Using a prior published case study, we estimate an average bias of 30%, with one order of magnitude for less sensitive compounds in some circumstances. A parameter-explicit solution is proposed in this work for completely removing the inherent bias generated in the log-linear calibration relationships. A simplified correction method is also suggested for cases where a comprehensive bias correction is not possible due to unknown uncertainties of calibration parameters, which is shown to eliminate the bias on average but not for each individual compound.

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Correcting bias in log-linear instrument calibrations in the context of chemical ionization mass spectrometry

Atmospheric Measurement Techniques ◽

10.5194/amt-14-6551-2021 ◽

2021 ◽

Vol 14 (10) ◽

pp. 6551-6560

Author(s):

Chenyang Bi ◽

Jordan E. Krechmer ◽

Manjula R. Canagaratna ◽

Gabriel Isaacman-VanWertz

Keyword(s):

Chemical Ionization ◽

Correction Method ◽

Operating Conditions ◽

Oxidation Products ◽

Mathematical Work ◽

Ionization Mass ◽

Individual Compound ◽

Linear Calibration ◽

Order Of Magnitude ◽

Log Linear

Abstract. Quantitative calibration of analytes using chemical ionization mass spectrometers (CIMSs) has been hindered by the lack of commercially available standards of atmospheric oxidation products. To accurately calibrate analytes without standards, techniques have been recently developed to log-linearly correlate analyte sensitivity with instrument operating conditions. However, there is an inherent bias when applying log-linear calibration relationships that is typically ignored. In this study, we examine the bias in a log-linear-based calibration curve based on prior mathematical work. We quantify the potential bias within the context of a CIMS-relevant relationship between analyte sensitivity and instrument voltage differentials. Uncertainty in three parameters has the potential to contribute to the bias, specifically the inherent extent to which the nominal relationship can capture true sensitivity, the slope of the relationship, and the voltage differential below which maximum sensitivity is achieved. Using a prior published case study, we estimate an average bias of 30 %, with 1 order of magnitude for less sensitive compounds in some circumstances. A parameter-explicit solution is proposed in this work for completely removing the inherent bias generated in the log-linear calibration relationships. A simplified correction method is also suggested for cases where a comprehensive bias correction is not possible due to unknown uncertainties of calibration parameters, which is shown to eliminate the bias on average but not for each individual compound.

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Measurements of volatile organic compounds over West Africa

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-10-3861-2010 ◽

2010 ◽

Vol 10 (2) ◽

pp. 3861-3892 ◽

Cited By ~ 8

Author(s):

J. G. Murphy ◽

D. E. Oram ◽

C. E. Reeves

Keyword(s):

Boundary Layer ◽

Volatile Organic Compounds ◽

Organic Compounds ◽

Marine Boundary Layer ◽

Deep Convection ◽

Proton Transfer Reaction ◽

Oxidation Products ◽

High Time Resolution ◽

Airborne Measurements ◽

Volatile Organic

Abstract. In this paper we describe measurements of volatile organic compounds (VOCs) made using a Proton Transfer Reaction Mass Spectrometer (PTR-MS) aboard the UK Facility for Atmospheric Airborne Measurements during the African Monsoon Multidisciplinary Analyses (AMMA) campaign. Observations were made during approximately 85 h of flying time between 17 July and 17 August 2006, above an area between 4° N and 18° N and 3° W and 4° E, encompassing ocean, mosaic forest, and the Sahel desert. High time resolution observations of counts at mass to charge (m/z) ratios of 42, 59, 69, 71, and 79 were used to calculate mixing ratios of acetonitrile, acetone, isoprene, the sum of methyl vinyl ketone and methacrolein, and benzene, respectively using laboratory-derived humidity-dependent calibration factors. Strong spatial associations between vegetation and isoprene and its oxidation products were observed in the boundary layer, consistent with biogenic emissions followed by rapid atmospheric oxidation. Acetonitrile, benzene, and acetone were all enhanced in airmasses which had been heavily influenced by biomass burning. Benzene and acetone were also elevated in airmasses with urban influence from cities such as Lagos, Cotonou, and Niamey. The observations provide evidence that both deep convection and mixing associated with fair-weather cumulus were responsible for vertical redistribution of VOCs emitted from the surface. Profiles over the ocean showed a depletion of acetone in the marine boundary layer, but no significant decrease for acetonitrile.

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Enhanced levels of nitrous acid during daytime derived from MAX-DOAS measurements during the AQABA campaign in late summer 2017

10.5194/egusphere-egu21-2571 ◽

2021 ◽

Author(s):

Steffen Dörner ◽

Sebastian Donner ◽

Lisa Behrens ◽

Steffen Beirle ◽

Sergey Osipov ◽

...

Keyword(s):

Nitrous Acid ◽

Arabian Gulf ◽

Late Summer ◽

Oil Fields ◽

Sufficient Information ◽

Ship Traffic ◽

Dust Clouds ◽

Clean Air ◽

Ship Route ◽

Set Up

<p>During the Air Quality and Climate Change in the Arabian Basin (AQABA) campaign a MAX-DOAS instrument was set up on board of the Kommandor Iona. The ship route covered a variety of regions with different atmospheric compositions: Clean air in the Mediterranean and the Arabian Sea, anthropogenic air pollution near the oil fields in the Arabian Gulf or in areas of dense ship traffic like the Suez Channel or the dust clouds of the nearby deserts in the Red sea. The measured spectra in the UV/VIS spectral range (302 to 467nm) provide sufficient information for the retrieval of aerosol and trace gas profiles. In this study, we focus on evidences of direct nitrous acid emission sources in harbor areas around Jeddah and Kuwait. Since HONO daytime chemistry is debated in recent literature and missing sources are being discussed, we compared the results of the MAX DOAS measurements to WRF-Chem model output in order to identify potential daytime sources in maritime/harbor regions.</p>

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OH and HO<sub>2</sub> radical chemistry in a midlatitude forest: Measurements and model comparisons

10.5194/acp-2019-726 ◽

2019 ◽

Cited By ~ 2

Author(s):

Michelle L. Lew ◽

Pamela S. Rickly ◽

Brandon P. Bottorff ◽

Sofia Sklaveniti ◽

Thierry Léonardis ◽

...

Keyword(s):

Atmospheric Chemistry ◽

Global Climate ◽

Oxidation Products ◽

Chemical Mechanism ◽

Ozone Production ◽

Peroxy Radicals ◽

Mixing Ratios ◽

Photolysis Rates ◽

Model Predictions ◽

Ho2 Radical

Abstract. Reactions of the hydroxyl (OH) and peroxy radicals (HO2 and RO2) play a central role in the chemistry of the atmosphere. In addition to controlling the lifetimes of many trace gases important to issues of global climate change, OH radical reactions initiate the oxidation of volatile organic compounds (VOCs) which can lead to the production of ozone and secondary organic aerosols in the atmosphere. Previous measurements of these radicals in forest environments characterized by high mixing ratios of isoprene and low mixing ratios of nitrogen oxides (NOx) have shown serious discrepancies with modeled concentrations. These results bring into question our understanding of the atmospheric chemistry of isoprene and other biogenic VOCs under low NOx conditions. During the summer of 2015, OH and HO2 radical concentrations as well as total OH reactivity were measured using Laser-Induced Fluorescence - Fluorescence Assay by Gas Expansion (LIF-FAGE) techniques as part of the Indiana Radical, Reactivity and Ozone Production Intercomparison (IRRONIC). This campaign took place in a forested area near the Indiana University, Bloomington campus characterized by high mixing ratios of isoprene and low mixing ratios of NOx. Supporting measurements of photolysis rates, VOCs, NOx, and other species were used to constrain a zero-dimensional box model based on the Regional Atmospheric Chemistry Mechanism (RACM2) and the Master Chemical Mechanism (MCM). Using an OH chemical scavenger technique, the study revealed the presence of an interference with the LIF-FAGE measurements of OH that increased with both ambient concentrations of ozone and temperature. Subtraction of the interference resulted in measured OH concentrations that were in better agreement with model predictions, although the model still underestimated the measured concentrations, likely due to an underestimation of the concentration of NO at this site. Measurements of HO2 radical concentrations during the campaign included a fraction of isoprene-based peroxy radicals (HO2* = HO2 + αRO2) and were found to agree with model predictions. On average, the measured reactivity was consistent with that calculated from measured OH sinks to within 20 %, with modeled oxidation products accounting for the missing reactivity, although significant missing reactivity (approximately 40 % of the total measured reactivity) was observed on some days.

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Thermal-Oxidation Stability of Soybean Germ Phytosterols in Different Lipid Matrixes

Molecules ◽

10.3390/molecules25184079 ◽

2020 ◽

Vol 25 (18) ◽

pp. 4079 ◽

Cited By ~ 1

Author(s):

Jingnan Chen ◽

Dami Li ◽

Guiyun Tang ◽

Jinfen Zhou ◽

Wei Liu ◽

...

Keyword(s):

Fatty Acids ◽

Olive Oil ◽

Thermal Oxidation ◽

Loss Rate ◽

Unsaturated Fatty Acids ◽

Oxidation Stability ◽

Oxidation Products ◽

Higher Temperature ◽

The Stability ◽

Thermal Oxidation Stability

The stability of soybean germ phytosterols (SGPs) in different lipid matrixes, including soybean germ oil, olive oil, and lard, was studied at 120, 150, and 180 °C. Results on the loss rate demonstrated that SGPs were most stable in olive oil, followed by soybean germ oil, and lard in a decreasing order. It is most likely that unsaturated fatty acids could oxidize first, compete with consumption of oxygen, and then spare phytosterols from oxidation. The oxidation products of SGPS in non-oil and oil systems were also quantified. The results demonstrated that at relatively lower temperatures (120 and 150 °C), SGPs’ oxidation products were produced the most in the non-oil system, followed by lard, soybean germ oil, and olive oil. This was consistent with the loss rate pattern of SGPs. At a relatively higher temperature of 180 °C, the formation of SGPs’ oxidation products in soybean germ oil was quantitatively the same as that in lard, implying that the temperature became a dominative factor rather than the content of unsaturated fatty acids of lipid matrixes in the oxidation of SGPs.

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Mitigation of Methane, NMVOCs and Odor Emissions in Active and Passive Biofiltration Systems at Municipal Solid Waste Landfills

Sustainability ◽

10.3390/su12083203 ◽

2020 ◽

Vol 12 (8) ◽

pp. 3203 ◽

Cited By ~ 4

Author(s):

Isabella Pecorini ◽

Elena Rossi ◽

Renato Iannelli

Keyword(s):

Organic Compounds ◽

Landfill Gas ◽

Emission Mitigation ◽

Oxidation Of Methane ◽

Volatile Organic ◽

Odor Emissions ◽

Municipal Solid Waste Landfills ◽

Odor Activity Value ◽

Oxidation Efficiency ◽

Solid Waste Landfills

Biofiltration systems are emerging technological solutions for the removal of methane and odors from landfill gas when flaring is no longer feasible. This work analyzed and compared two full-scale biofiltration systems: biofilter and biowindows. The emission mitigation of methane, non-methane volatile organic compounds (NMVOCs) and odors during a two-year management and monitoring period was studied. In addition to diluted methane, more than 50 NMVOCs have been detected in the inlet raw landfill gas and the sulfur compounds resulted in the highest odor activity value. Both systems, biofilter and biowindows, were effective for the oxidation of methane (58.1% and 88.05%, respectively), for the mitigation of NMVOCs (higher than 80%) and odor reduction (99.84% and 93.82% respectively). As for the biofilter monitoring, it was possible to define the oxidation efficiency trend and in fact to guarantee that for an oxidation efficiency of 80%, the methane load must be less than 6.5 g CH4/m2h with an oxidation rate of 5.2 g CH4/m2h.

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Contributions to OH reactivity from unexplored volatile organic compounds measured by PTR-ToF-MS – A case study in a suburban forest of the Seoul Metropolitan Area during KORUS-AQ 2016

10.5194/acp-2020-174 ◽

2020 ◽

Cited By ~ 1

Author(s):

Dianne Sanchez ◽

Roger Seco ◽

Dasa Gu ◽

Alex Guenther ◽

John Mak ◽

...

Keyword(s):

Volatile Organic Compounds ◽

Organic Compounds ◽

Mass Spectrometer ◽

Metropolitan Area ◽

Forest Canopy ◽

Oxidation Products ◽

Ionization Mass ◽

Seoul Metropolitan Area ◽

Volatile Organic ◽

Tof Ms

Abstract. We report OH reactivity observations by a chemical ionization mass spectrometer – comparative reactivity method (CIMS-CRM) instrument in a suburban forest of the Seoul Metropolitan Area (SMA) during Korea US Air Quality Study (KORUS-AQ 2016) from mid-May to mid-June of 2016. A comprehensive observational suite was deployed to quantify reactive trace gases inside of the forest canopy including a high-resolution proton transfer reaction time of flight mass spectrometer (PTR-ToF-MS). An average OH reactivity of 30.7 ± 5.1 s−1 was observed, while the OH reactivity calculated from CO, NO + NO2 (NOx), ozone (O3), sulfur dioxide (SO2), and 14 volatile organic compounds (VOCs) was 11.8 ± 1.0 s−1. An analysis of 346 peaks from the PTR-ToF-MS accounted for an additional 6.0 ± 2.2 s−1 of the total measured OH reactivity, leaving 42.0 % missing OH reactivity. The missing OH reactivity most likely comes from VOC oxidation products of both biogenic and anthropogenic origin.

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