scholarly journals Oxidation of low-molecular weight organic compounds in cloud droplets: global impact on tropospheric oxidants

2020 ◽  
Author(s):  
Simon Rosanka ◽  
Rolf Sander ◽  
Bruno Franco ◽  
Catherine Wespes ◽  
Andreas Wahner ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Aqueous Phase ◽  
Oxidation Products ◽  
Atmospheric Models ◽  
Cloud Droplets ◽  
Global Impact ◽  
Budget Analysis ◽  
Volatile Organic ◽  
Phase Chemical

Abstract. In liquid cloud droplets, superoxide anion (O−2(aq)) is known to quickly consume ozone (O3(aq)), which is relatively insoluble. The significance of this reaction as tropospheric O3 sink is sensitive to the abundance of O−2(aq) and therefore to the production of its main precursor, hydroperoxyl radical (HO2(aq)). The aqueous-phase oxidation of oxygenated volatile organic compounds (OVOCs) is the major source of HO2(aq) in cloud droplets. Hence, the lack of explicit aqueous-phase chemical kinetics in global atmospheric models leads to a general underestimation of clouds as O3 sinks. In this study, the importance of in-cloud OVOC oxidation for tropospheric composition is assessed by using the Chemistry As A Boxmodel Application (CAABA) and the global atmospheric model ECHAM/MESSy (EMAC), which are both capable of explicitly representing the relevant chemical transformations. For this analysis, three different in-cloud oxidation mechanisms are employed: (1) one including the basic oxidation of SO2(aq) via O3(aq) and H2O2(aq), which thus represents the capabilities of most global models, (2) the more advanced standard EMAC mechanism, which includes inorganic chemistry and simplified degradation of methane oxidation products, and (3) the detailed in-cloud OVOC oxidation scheme Jülich Aqueous-phase Mechanism of Organic Chemistry (JAMOC). By using EMAC, the global impact of each mechanism is assessed focusing mainly on tropospheric volatile organic compounds (VOCs), HOx (HOx = OH+HO2), and O3. This is achieved by performing a detailed HOx and O3 budget analysis in the gas- and aqueous-phase. The resulting changes are evaluated against O3 and methanol (CH3OH) satellite observations from the Infrared Atmospheric Sounding Interferometer (IASI) for 2015. In general, the explicit in-cloud oxidation leads to an overall reduction of predicted OVOCs levels, and reduces EMAC's overestimation of some OVOCs in the tropics. The in-cloud OVOC oxidation shifts the HO2 production from the gas- to the aqueous-phase. As a result, the O3 budget is perturbed with scavenging being enhanced and the gas-phase chemical losses being reduced. With the simplified in-cloud chemistry, about 13 Tg a−1 of O3 are scavenged, which increases to 336 Tg a−1 when JAMOC is used. The highest O3 reduction of 12 % is predicted in the upper troposphere/lower stratosphere (UTLS). These changes in the free troposphere significantly reduce the modelled tropospheric ozone columns, which are known to be generally overestimated by EMAC and other global atmospheric models.

scholarly journals Measurements of volatile organic compounds over West Africa

2010 ◽  
Vol 10 (2) ◽  
pp. 3861-3892 ◽  
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.

scholarly journals 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

2020 ◽  
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.

scholarly journals OH reactivity and concentrations of Biogenic Volatile Organic Compounds in a Mediterranean forest of downy oak trees

2015 ◽  
Vol 15 (16) ◽  
pp. 22047-22095 ◽  
Author(s):  
N. Zannoni ◽  
V. Gros ◽  
M. Lanza ◽  
R. Sarda ◽  
B. Bonsang ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Degradation Products ◽  
Ambient Air ◽  
Oxidation Products ◽  
Deciduous Tree ◽  
Forest Site ◽  
Mediterranean Forests ◽  
Oak Trees ◽  
Volatile Organic

Abstract. Understanding the processes between the biosphere and the atmosphere is challenged by the difficulty to determine with enough accuracy the composition of the atmosphere. Total OH reactivity, which is defined as the total loss of the hydroxyl radical in the atmosphere, has proved to be an excellent tool to identify indirectly the important reactive species in ambient air. High levels of unknown reactivity were found in several forests worldwide and were often higher than at urban sites. Such results demonstrated the importance of OH reactivity for characterizing two of the major unknowns currently present associated to forests: the set of primary emissions from the canopy to the atmosphere and biogenic compounds oxidation pathways. Previous studies also highlighted the need to quantify OH reactivity and missing OH reactivity at more forested sites. Our study presents results of a field experiment conducted during late spring 2014 at the forest site at the Observatoire de Haute Provence, OHP, France. The forest is mainly composed of downy oak trees, a deciduous tree species characteristic of the Mediterranean region. We deployed the Comparative Reactivity Method and a set of state-of-the-art techniques such as Proton Transfer Reaction-Mass Spectrometry and Gas Chromatography to measure the total OH reactivity, the concentration of volatile organic compounds and main atmospheric constituents at the site. We sampled the air masses at two heights: 2 m, i.e. inside the canopy, and 10 m, i.e. above the canopy, where the mean canopy height is 5 m. We found that the OH reactivity at the site mainly depended on the main primary biogenic species emitted by the forest, which was isoprene and to a lesser extent by its degradation products and long lived atmospheric compounds (up to 26 % during daytime). We determined that the daytime total measured reactivity equaled the calculated reactivity obtained from the concentrations of the compounds measured at the site. Hence, no significant missing reactivity is reported in this specific site, neither inside, nor above the canopy. However, during two nights we reported a missing fraction of OH reactivity up to 50 %, possibly due to unmeasured oxidation products. Our results confirm the weak intra canopy oxidation, already suggested in a previous study focused on isoprene fluxes. They also demonstrate how helpful can be the OH reactivity as a tool to clearly characterize the suite of species present in the atmosphere. We show that our result of reactivity is among the highest reported in forests worldwide and stress the importance to quantify OH reactivity at more and diverse Mediterranean forests.

Inhibition of Atmospheric Aqueous Phase Autoxidation of Sulphur Dioxide by Volatile Organic Compounds: Mono-, di- and Tri-Substituted Benzenes and Benzoic Acids

2017 ◽  
Vol 42 (2) ◽  
pp. 111-125 ◽  
Author(s):  
Vimlesh Kumar Meena ◽  
Yogpal Dhayal ◽  
Deepak Singh Rathore ◽  
C.P. Singh Chandel ◽  
K.S. Gupta
Keyword(s):  
Volatile Organic Compounds ◽  
Benzoic Acid ◽  
Organic Compounds ◽  
Aqueous Phase ◽  
Methoxy Group ◽  
B Values ◽  
First Order ◽  
Volatile Organic ◽  
Major Acid ◽  
Hydroxyl Compounds

Like many other volatile organic compounds (VOCs), the methoxy derivatives of benzene and benzoic acid are found in the atmosphere and, therefore, looking to their possible intervention in aqueous phase atmospheric oxidation of the major acid rain precursor, SO2, by oxygen, the kinetics of SO2 [hereafter referred to as S(IV)] autoxidation have been studied in the presence of methoxybenzene (anisole) and disubstituted 1,2-dimethoxybenzene, 1,3-dimethoxybenzene and 1,4-dimethoxybenzene. The effects of benzoic acid and its 2,6-dimethoxy, 3,4-dimethoxy, 2,3,4-trimethoxy and 2,4,5-trimethoxy derivatives have also been examined, as have the influences of 4-hydroxybenzoic acid, benzanilide and o-sulfobenzimide. As the methoxy group is known to influence the reaction SO4–· + organics [Formula: see text] SO42– + non-chain products, to understand the degree of influence of the methoxy group on the inhibition of this reaction, this series of methoxy compounds was selected. The kinetics were first-order in S(IV). Most of the VOCs inhibited S(IV) autoxidation, except benzanilide and o-sulfobenzimide, in accordance with kobs = k0/(1 + B [Inh]), where kobs and k0 are the first-order rate constants in the presence and absence of VOCs respectively and B is the inhibition parameter. The most interesting feature of this work is that, despite the high kinh values, the B values are unexpectedly quite low and benzanilide and o-sulfobenzimide showed no effect. The B values appear to be independent of kinh, which is opposite to that found in the case of a series of hydroxyl compounds. It appears probable that additional steps involving peroxy intermediates are involved.

Experimental determination of the partitioning coefficient of β-pinene oxidation products in SOAs

2015 ◽  
Vol 17 (22) ◽  
pp. 14796-14804 ◽  
Author(s):  
Thorsten Hohaus ◽  
Iulia Gensch ◽  
Joel Kimmel ◽  
Douglas R. Worsnop ◽  
Astrid Kiendler-Scharr
Keyword(s):  
Volatile Organic Compounds ◽  
Experimental Determination ◽  
Organic Compounds ◽  
Oxidation Products ◽  
Particle Phase ◽  
Partitioning Coefficient ◽  
Volatile Organic ◽  
Measured Particle

Measured particle phase concentrations of semi-volatile organic compounds exceed those predicted by absorption equilibrium gas-particle partitioning by orders of magnitude.

scholarly journals Direct ecosystem fluxes of volatile organic compounds from oil palms in South-East Asia

2011 ◽  
Vol 11 (17) ◽  
pp. 8995-9017 ◽  
Author(s):  
P. K. Misztal ◽  
E. Nemitz ◽  
B. Langford ◽  
C. F. Di Marco ◽  
G. J. Phillips ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Canopy Temperature ◽  
Proton Transfer Reaction ◽  
Oxidation Products ◽  
Palm Trees ◽  
Volatile Organic ◽  
Resistance Approach ◽  
Oil Palms ◽  
Malaysian Borneo

Abstract. This paper reports the first direct eddy covariance fluxes of reactive biogenic volatile organic compounds (BVOCs) from oil palms to the atmosphere using proton-transfer-reaction mass spectrometry (PTR-MS), measured at a plantation in Malaysian Borneo. At midday, net isoprene flux constituted the largest fraction (84 %) of all emitted BVOCs measured, at up to 30 mg m−2 h−1 over 12 days. By contrast, the sum of its oxidation products methyl vinyl ketone (MVK) and methacrolein (MACR) exhibited clear deposition of 1 mg m−2 h−1, with a small average canopy resistance of 230 s m−1. Approximately 15 % of the resolved BVOC flux from oil palm trees could be attributed to floral emissions, which are thought to be the largest reported biogenic source of estragole and possibly also toluene. Although on average the midday volume mixing ratio of estragole exceeded that of toluene by almost a factor of two, the corresponding fluxes of these two compounds were nearly the same, amounting to 0.81 and 0.76 mg m−2 h−1, respectively. By fitting the canopy temperature and PAR response of the MEGAN emissions algorithm for isoprene and other emitted BVOCs a basal emission rate of isoprene of 7.8 mg m−2 h−1 was derived. We parameterise fluxes of depositing compounds using a resistance approach using direct canopy measurements of deposition. Consistent with Karl et al. (2010), we also propose that it is important to include deposition in flux models, especially for secondary oxidation products, in order to improve flux predictions.

scholarly journals Measurements of volatile organic compounds over West Africa

2010 ◽  
Vol 10 (12) ◽  
pp. 5281-5294 ◽  
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 (VOC) 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 VOC emitted from the surface. Profiles over the ocean showed a depletion of acetone in the marine boundary layer, but no significant decrease for acetonitrile.

scholarly journals Surface and boundary layer exchanges of volatile organic compounds, nitrogen oxides and ozone during the GABRIEL campaign

2008 ◽  
Vol 8 (20) ◽  
pp. 6223-6243 ◽  
Author(s):  
L. Ganzeveld ◽  
G. Eerdekens ◽  
G. Feig ◽  
H. Fischer ◽  
H. Harder ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Residual Layer ◽  
Oxidation Products ◽  
Emission Flux ◽  
Mixing Ratios ◽  
Volatile Organic ◽  
Isoprene Oxidation ◽  
Isoprene Oxidation Products

Abstract. We present an evaluation of sources, sinks and turbulent transport of nitrogen oxides, ozone and volatile organic compounds (VOC) in the boundary layer over French Guyana and Suriname during the October 2005 GABRIEL campaign by simulating observations with a single-column chemistry and climate model (SCM) along a zonal transect. Simulated concentrations of O3 and NO as well as NO2 photolysis rates over the forest agree well with observations when a small soil-biogenic NO emission flux was applied. This suggests that the photochemical conditions observed during GABRIEL reflect a pristine tropical low-NOx regime. The SCM uses a compensation point approach to simulate nocturnal deposition and daytime emissions of acetone and methanol and produces daytime boundary layer mixing ratios in reasonable agreement with observations. The area average isoprene emission flux, inferred from the observed isoprene mixing ratios and boundary layer height, is about half the flux simulated with commonly applied emission algorithms. The SCM nevertheless simulates too high isoprene mixing ratios, whereas hydroxyl concentrations are strongly underestimated compared to observations, which can at least partly explain the discrepancy. Furthermore, the model substantially overestimates the isoprene oxidation products methlyl vinyl ketone (MVK) and methacrolein (MACR) partly due to a simulated nocturnal increase due to isoprene oxidation. This increase is most prominent in the residual layer whereas in the nocturnal inversion layer we simulate a decrease in MVK and MACR mixing ratios, assuming efficient removal of MVK and MACR. Entrainment of residual layer air masses, which are enhanced in MVK and MACR and other isoprene oxidation products, into the growing boundary layer poses an additional sink for OH which is thus not available for isoprene oxidation. Based on these findings, we suggest pursuing measurements of the tropical residual layer chemistry with a focus on the nocturnal depletion of isoprene and its oxidation products.

scholarly journals A novel Whole Air Sample Profiler (WASP) for the quantification of volatile organic compounds in the boundary layer

2013 ◽  
Vol 6 (10) ◽  
pp. 2703-2712 ◽  
Author(s):  
J. E. Mak ◽  
L. Su ◽  
A. Guenther ◽  
T. Karl
Keyword(s):  
Boundary Layer ◽  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Flow Rate ◽  
Gas Analysis ◽  
Oxidation Products ◽  
Outer Diameter ◽  
Sampling System ◽  
Important Region ◽  
Volatile Organic

Abstract. The emission and fate of reactive volatile organic compounds (VOCs) is of inherent interest to those studying chemical biosphere–atmosphere interactions. In-canopy VOC observations are obtainable using tower-based samplers, but the lack of suitable sampling systems for the full boundary layer has limited the availability of data characterizing the vertical structure of such gases above the canopy height and still in the boundary layer. This is an important region where many reactive VOCs are oxidized or otherwise removed. Here we describe an airborne sampling system designed to collect a vertical profile of air into a 3/8 in. OD (outer diameter) tube 150 m in length. The inlet ram air pressure is used to flow sampled air through the tube, which results in a varying flow rate based on aircraft speed and altitude. Since aircraft velocity decreases during ascent, it is necessary to account for the variable flow rate into the tube. This is accomplished using a reference gas that is pulsed into the air stream so that the precise altitude of the collected air can be reconstructed post-collection. The pulsed injections are also used to determine any significant effect from diffusion/mixing within the sampling tube, either during collection or subsequent extraction for gas analysis. This system has been successfully deployed, and we show some measured vertical profiles of isoprene and its oxidation products methacrolein and methyl vinyl ketone from a mixed canopy near Columbia, Missouri.

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