73 results on '"Acton, W. Joe F."'
Search Results
52. Observations of speciated isoprene nitrates in Beijing: implications for isoprene chemistry
- Author
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Reeves, Claire E., primary, Mills, Graham P., additional, Whalley, Lisa K., additional, Acton, W. Joe F., additional, Bloss, William J., additional, Crilley, Leigh R., additional, Grimmond, Sue, additional, Heard, Dwayne E., additional, Hewitt, C. Nicholas, additional, Hopkins, James R., additional, Kotthaus, Simone, additional, Kramer, Louisa J., additional, Jones, Roderic L., additional, Lee, James D., additional, Liu, Yanhui, additional, Ouyang, Bin, additional, Slater, Eloise, additional, Squires, Freya, additional, Wang, Xinming, additional, Woodward-Massey, Robert, additional, and Ye, Chunxiang, additional
- Published
- 2020
- Full Text
- View/download PDF
53. Observations of highly oxidized molecules and particle nucleation in the atmosphere of Beijing
- Author
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Brean, James, primary, Harrison, Roy M., additional, Shi, Zongbo, additional, Beddows, David C. S., additional, Acton, W. Joe F., additional, Hewitt, C. Nicholas, additional, Squires, Freya A., additional, and Lee, James, additional
- Published
- 2019
- Full Text
- View/download PDF
54. Validity and limitations of simple reaction kinetics to calculate concentrations of organic compounds from ion counts in PTR-MS
- Author
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Holzinger, Rupert, primary, Acton, W. Joe F., additional, Bloss, William J., additional, Breitenlechner, Martin, additional, Crilley, Leigh R., additional, Dusanter, Sébastien, additional, Gonin, Marc, additional, Gros, Valerie, additional, Keutsch, Frank N., additional, Kiendler-Scharr, Astrid, additional, Kramer, Louisa J., additional, Krechmer, Jordan E., additional, Languille, Baptiste, additional, Locoge, Nadine, additional, Lopez-Hilfiker, Felipe, additional, Materić, Dušan, additional, Moreno, Sergi, additional, Nemitz, Eiko, additional, Quéléver, Lauriane L. J., additional, Sarda Esteve, Roland, additional, Sauvage, Stéphane, additional, Schallhart, Simon, additional, Sommariva, Roberto, additional, Tillmann, Ralf, additional, Wedel, Sergej, additional, Worton, David R., additional, Xu, Kangming, additional, and Zaytsev, Alexander, additional
- Published
- 2019
- Full Text
- View/download PDF
55. Validity and limitations of simple reaction kinetics to calculate concentrations of organic compounds from ion counts in PTR-MS
- Author
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Sub Atmospheric physics and chemistry, Marine and Atmospheric Research, Holzinger, Rupert, Acton, W. Joe F., Bloss, William J., Breitenlechner, Martin, Crilley, Leigh R., Dusanter, Sebastien, Gonin, Marc, Gros, Valerie, Keutsch, Frank N., Kiendler-Scharr, Astrid, Kramer, Louisa J., Krechmer, Jordan E., Languille, Baptiste, Locoge, Nadine, Lopez-Hilfiker, Felipe, Materic, Dusan, Moreno, Sergi, Nemitz, Eiko, Quelever, Lauriane L. J., Esteve, Roland Sarda, Sauvage, Stephane, Schallhart, Simon, Sommariva, Roberto, Tillmann, Ralf, Wedel, Sergej, Worton, David R., Xu, Kangming, Zaytsev, Alexander, Sub Atmospheric physics and chemistry, Marine and Atmospheric Research, Holzinger, Rupert, Acton, W. Joe F., Bloss, William J., Breitenlechner, Martin, Crilley, Leigh R., Dusanter, Sebastien, Gonin, Marc, Gros, Valerie, Keutsch, Frank N., Kiendler-Scharr, Astrid, Kramer, Louisa J., Krechmer, Jordan E., Languille, Baptiste, Locoge, Nadine, Lopez-Hilfiker, Felipe, Materic, Dusan, Moreno, Sergi, Nemitz, Eiko, Quelever, Lauriane L. J., Esteve, Roland Sarda, Sauvage, Stephane, Schallhart, Simon, Sommariva, Roberto, Tillmann, Ralf, Wedel, Sergej, Worton, David R., Xu, Kangming, and Zaytsev, Alexander
- Published
- 2019
56. Validity and limitations of simple reaction kinetics to calculate concentrations of organic compounds from ion counts in PTR-MS
- Author
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Holzinger, Rupert, Acton, W. Joe F., Bloss, William J., Breitenlechner, Martin, Crilley, Leigh R., Dusanter, Sébastien, Gonin, Marc, Gros, Valerie, Keutsch, Frank N., Kiendler-Scharr, Astrid, Kramer, Louisa J., Krechmer, Jordan E., Languille, Baptiste, Locoge, Nadine, Lopez-Hilfiker, Felipe, Materić, Dušan, Moreno, Sergi, Nemitz, Eiko, Quéléver, Lauriane L.J., Sarda Esteve, Roland, Sauvage, Stéphane, Schallhart, Simon, Sommariva, Roberto, Tillmann, Ralf, Wedel, Sergej, Worton, David R., Xu, Kangming, Zaytsev, Alexander, Holzinger, Rupert, Acton, W. Joe F., Bloss, William J., Breitenlechner, Martin, Crilley, Leigh R., Dusanter, Sébastien, Gonin, Marc, Gros, Valerie, Keutsch, Frank N., Kiendler-Scharr, Astrid, Kramer, Louisa J., Krechmer, Jordan E., Languille, Baptiste, Locoge, Nadine, Lopez-Hilfiker, Felipe, Materić, Dušan, Moreno, Sergi, Nemitz, Eiko, Quéléver, Lauriane L.J., Sarda Esteve, Roland, Sauvage, Stéphane, Schallhart, Simon, Sommariva, Roberto, Tillmann, Ralf, Wedel, Sergej, Worton, David R., Xu, Kangming, and Zaytsev, Alexander
- Abstract
In September 2017, we conducted a proton-transfer-reaction mass-spectrometry (PTR-MS) intercomparison campaign at the CESAR observatory, a rural site in the central Netherlands near the village of Cabauw. Nine research groups deployed a total of 11 instruments covering a wide range of instrument types and performance. We applied a new calibration method based on fast injection of a gas standard through a sample loop. This approach allows calibrations on timescales of seconds, and within a few minutes an automated sequence can be run allowing one to retrieve diagnostic parameters that indicate the performance status. We developed a method to retrieve the mass-dependent transmission from the fast calibrations, which is an essential characteristic of PTR-MS instruments, limiting the potential to calculate concentrations based on counting statistics and simple reaction kinetics in the reactor/drift tube. Our measurements show that PTR-MS instruments follow the simple reaction kinetics if operated in the standard range for pressures and temperature of the reaction chamber (i.e. 1–4 mbar, 30–120∘, respectively), as well as a reduced field strength E∕N in the range of 100–160 Td. If artefacts can be ruled out, it becomes possible to quantify the signals of uncalibrated organics with accuracies better than ±30 %. The simple reaction kinetics approach produces less accurate results at E∕N levels below 100 Td, because significant fractions of primary ions form water hydronium clusters. Deprotonation through reactive collisions of protonated organics with water molecules needs to be considered when the collision energy is a substantial fraction of the exoergicity of the proton transfer reaction and/or if protonated organics undergo many collisions with water molecules.
- Published
- 2019
57. Observations of highly oxidized molecules and particle nucleation in the atmosphere of Beijing
- Author
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Brean, James, Harrison, Roy M., Shi, Zongbo, Beddows, David C. S., Acton, W. Joe F., Hewitt, C. N., Squires, Freya, Lee, James, Brean, James, Harrison, Roy M., Shi, Zongbo, Beddows, David C. S., Acton, W. Joe F., Hewitt, C. N., Squires, Freya, and Lee, James
- Abstract
Particle nucleation is one of the main sources of atmospheric particulate matter by number, with new particles having great relevance for human health and climate. Highly oxidised multifunctional organic molecules (HOMs) have been recently identified as key constituents in the growth, and, sometimes, in initial formation of new particles. While there have been many studies of HOMs in atmospheric chambers, flow tubes and clean environments, analyses of data from polluted environments are scarce. Here, measurements of HOMs and particle size distributions down to small molecular clusters are presented alongside VOC and trace gas data from a campaign in Beijing. Many gas phase HOMs have been characterised and their temporal trends and behaviours analysed in the context of new particle formation. The HOMs identified have a comparable degree of oxidation to those seen in other, cleaner, environments, likely due to an interplay between the higher temperatures facilitating rapid hydrogen abstractions and the higher concentrations of NOx and other RO2. terminators ending the autoxidation sequence more rapidly. Our data indicate that alkylbenzenes, monoterpenes, and isoprene are important precursor VOCs for HOMs in Beijing. Many of the C5 and C10 compounds derived from isoprene and monoterpenes have a slightly greater degree of average oxidation state of carbon compared to those from other precursors. Most HOMs except for large dimers have daytime peak concentrations, indicating the importance of OH. chemistry in the formation of HOMs, as O3 is lower on the days with higher HOM concentrations; similarly, VOC concentrations are lower on the days with higher HOM concentrations. The daytime peaks of HOMs coincide with the growth of freshly formed new particles, and their initial formation coincides with the peak in sulphuric acid vapours, suggesting that the nucleation process is sulphuric acid-dependent, with HOMs contributing to subsequent particle growth.
- Published
- 2019
58. Seasonal analysis of submicron aerosol in Old Delhi using high-resolution aerosol mass spectrometry: chemical characterisation, source apportionment and new marker identification.
- Author
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Cash, James M., Langford, Ben, Di Marco, Chiara, Mullinger, Neil J., Allan, James, Reyes-Villegas, Ernesto, Joshi, Ruthambara, Heal, Mathew R., Acton, W. Joe F., Hewitt, C. Nicholas, Misztal, Pawel K., Drysdale, Will, Mandal, Tuhin K., Shivani, Gadi, Ranu, Gurjar, Bhola Ram, and Nemitz, Eiko
- Subjects
INCINERATION ,MASS spectrometry ,POLLUTION source apportionment ,AEROSOL analysis ,SEASONS ,CARBONACEOUS aerosols ,NITROGEN oxides ,COMPRESSED natural gas - Abstract
We present the first real-time composition of submicron particulate matter (PM 1) in Old Delhi using high-resolution aerosol mass spectrometry (HR-AMS). Old Delhi is one of the most polluted locations in the world, and PM 1 concentrations reached ∼ 750 µ g m -3 during the most polluted period, the post-monsoon period, where PM 1 increased by 188 % over the pre-monsoon period. Sulfate contributes the largest inorganic PM 1 mass fraction during the pre-monsoon (24 %) and monsoon (24 %) periods, with nitrate contributing most during the post-monsoon period (8 %). The organics dominate the mass fraction (54 %–68 %) throughout the three periods, and, using positive matrix factorisation (PMF) to perform source apportionment analysis of organic mass, two burning-related factors were found to contribute the most (35 %) to the post-monsoon increase. The first PMF factor, semi-volatility biomass burning organic aerosol (SVBBOA), shows a high correlation with Earth observation fire counts in surrounding states, which links its origin to crop residue burning. The second is a solid fuel OA (SFOA) factor with links to local open burning due to its high composition of polyaromatic hydrocarbons (PAHs) and novel AMS-measured marker species for polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). Two traffic factors were resolved: one hydrocarbon-like OA (HOA) factor and another nitrogen-rich HOA (NHOA) factor. The N compounds within NHOA were mainly nitrile species which have not previously been identified within AMS measurements. Their PAH composition suggests that NHOA is linked to diesel and HOA to compressed natural gas and petrol. These factors combined make the largest relative contribution to primary PM 1 mass during the pre-monsoon and monsoon periods while contributing the second highest in the post-monsoon period. A cooking OA (COA) factor shows strong links to the secondary factor, semi-volatility oxygenated OA (SVOOA). Correlations with co-located volatile organic compound (VOC) measurements and AMS-measured organic nitrogen oxides (OrgNO) suggest SVOOA is formed from aged COA. It is also found that a significant increase in chloride concentrations (522 %) from pre-monsoon to post-monsoon correlates well with SVBBOA and SFOA, suggesting that crop residue burning and open waste burning are responsible. A reduction in traffic emissions would effectively reduce concentrations across most of the year. In order to reduce the post-monsoon peak, sources such as funeral pyres, solid waste burning and crop residue burning should be considered when developing new air quality policy. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
59. Supplementary material to "Observations of Highly Oxidised Molecules and Particle Nucleation in the Atmosphere of Beijing"
- Author
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Brean, James, primary, Harrison, Roy M., additional, Shi, Zongbo, additional, Beddows, David C. S., additional, Acton, W. Joe F., additional, and Hewitt, C. Nicholas, additional
- Published
- 2019
- Full Text
- View/download PDF
60. Supplementary material to "Validity and limitations of simple reaction kinetics to calculate concentrations of organic compounds from ion counts in PTR-MS"
- Author
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Holzinger, Rupert, primary, Acton, W. Joe F., additional, Bloss, William J., additional, Breitenlechner, Martin, additional, Crilley, Leigh R., additional, Dusanter, Sébastien, additional, Gonin, Marc, additional, Gros, Valerie, additional, Keutsch, Frank N., additional, Kiendler-Scharr, Astrid, additional, Kramer, Louisa J., additional, Krechmer, Jordan E., additional, Languille, Baptiste, additional, Locoge, Nadine, additional, Lopez-Hilfiker, Felipe, additional, Materić, Dušan, additional, Moreno, Sergi, additional, Nemitz, Eiko, additional, Quéléver, Lauriane L. J., additional, Sarda Esteve, Roland, additional, Sauvage, Stéphane, additional, Schallhart, Simon, additional, Sommariva, Roberto, additional, Tillmann, Ralf, additional, Wedel, Sergej, additional, Worton, David R., additional, Xu, Kangming, additional, and Zaytsev, Alexander, additional
- Published
- 2019
- Full Text
- View/download PDF
61. Emissions of non-methane volatile organic compounds from combustion of domestic fuels in Delhi, India.
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Stewart, Gareth J., Acton, W. Joe F., Nelson, Beth S., Vaughan, Adam R., Hopkins, James R., Arya, Rahul, Mondal, Arnab, Jangirh, Ritu, Ahlawat, Sakshi, Yadav, Lokesh, Sharma, Sudhir K., Dunmore, Rachel E., Yunus, Siti S. M., Hewitt, C. Nicholas, Nemitz, Eiko, Mullinger, Neil, Gadi, Ranu, Sahu, Lokesh. K., Tripathi, Nidhi, and Rickard, Andrew R.
- Abstract
29 different fuel types used in residential dwellings in northern India were collected from across New Delhi (76 samples in total). Emission factors of a wide range of non-methane volatile organic compounds (NMVOCs) (192 compounds in total) were measured during controlled burning experiments using dual-channel gas chromatography with flame ionisation detection (DC-GD-FID), two-dimensional gas chromatography (GCxGC-FID), proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS) and solid-phase extraction two-dimensional gas chromatography with time-of-flight mass spectrometry (SPE-GCxGC-ToF-MS). 94% quantification was achieved on average across all fuel types. The largest contributors to emissions from most fuel types were small non-aromatic oxygenated species, phenolics and furanics. The emission factors (in g kg
-1 ) for total gas-phase NMVOCs were: fuel wood (18.7, 4.3-96.7), cow dung cake (62.0, 35.3-83.0), crop residue (37.9, 8.9-73.8), charcoal (5.4, 2.4-7.9), sawdust (72.4, 28.6-115.5), municipal solid waste (87.3, 56.6-119.1) and liquified petroleum gas (5.7, 1.9-9.8). [ABSTRACT FROM AUTHOR]- Published
- 2020
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62. PM1 composition and source apportionment at two sites in Delhi, India across multiple seasons.
- Author
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Reyes-Villegas, Ernesto, Panda, Upasana, Darbyshire, Eoghan, Cash, James M., Joshi, Rutambhara, Langford, Ben, Marco, Chiara F. Di, Mullinger, Neil, Acton, W. Joe F., Drysdale, Will, Nemitz, Eiko, Flynn, Michael, Voliotis, Aristeidis, McFiggans, Gordon, Coe, Hugh, Lee, James, Hewitt, C. Nicholas, Heal, Mathew R., Gunthe, Sachin S, and Shivani
- Abstract
Air pollution in urban environments has been shown to have a negative impact on air quality and human health, particularly in megacities. Over recent decades, Delhi, India has suffered high atmospheric pollution, with significant particulate matter (PM) concentrations as result of anthropogenic activities. Organic aerosols (OA) are composed of thousands of different chemical species and are one of the main constituents of submicron particles. However, quantitative knowledge of OA composition, their sources and processes in urban environments is still limited. This is important particularly in India, as Delhi is a massive, inhomogeneous conurbation, which we would expect that the apportionment and concentrations will vary depending on where in Delhi the measurements/source apportionment is performed, indicating the need of multi-site measurements. This study presents the first multisite analysis carried out in India over different seasons, with a focus on identifying OA sources. The measurements were taken during 2018 at two sites in Delhi, India. One site was located at the India Meteorological Department, New Delhi (ND). The other site was located at the Indira Gandhi Delhi Technical University for Women, Old Delhi (OD). Non-refractory submicron aerosol (NR-PM1) concentrations (ammonium, nitrate, sulphate, chloride and organic aerosols) of four aerosol mass spectrometers were analysed. Collocated measurements of VOC, black carbon, NOx and CO were performed. Positive matrix factorization (PMF) analysis was performed to separate the organic fraction, identifying a number of conventional factors: hydrocarbon-like OA (HOA) related to traffic emissions, biomass burning OA (BBOA), cooking OA (COA) and secondary OA (SOA). A composition-based estimate of PMi is defined by combining BC and NR-PMi (C-PMi = BC + NR-PM1). No significant difference was observed on C-PMi concentrations between sites; OD (142 +/- 117 ^g.m
-3 ) compared to ND (123 +/- 71 ^g.m-3 ), from post-monsoon measurements. A wider variability was observed between seasons, where pre-monsoon and monsoon showed C-PM1 concentrations lower than 60 ^g.m-3 . A seasonal variation in C-PM1 composition was observed; SO42- showed a high contribution over pre-monsoon and monsoon seasons while NO3- and Cl- had a higher contribution in winter and post- monsoon. The main primary aerosol source was from traffic, which is consistent with the PMF analysis and aethalometer model analysis. Thus, in order to reduce PM1 concentrations in Delhi through local emission controls traffic emissions control offers the greatest opportunity. PMF-AMS mass spectra will help to improve future aerosol source apportionment studies. The information generated in this study increases our understanding of PM1 composition and OA sources in Delhi, India. Furthermore, the scientific findings provide significant information to strengthen legislation that aims to improve air quality in India. [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
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63. Emissions of intermediate-volatility and semi-volatile organic compounds from domestic fuels used in Delhi, India.
- Author
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Stewart, Gareth J., Nelson, Beth S., Acton, W. Joe F., Vaughan, Adam R., Farren, Naomi J., Hopkins, James R., Ward, Martyn W., Swift, Stefan J., Arya, Rahul, Mondal, Arnab, Jangirh, Ritu, Ahlawat, Sakshi, Yadav, Lokesh, Sharma, Sudhir K., Yunus, Siti S. M., Hewitt, C. Nicholas, Nemitz, Eiko, Mullinger, Neil, Gadi, Ranu, and Sahu, Lokesh. K.
- Abstract
Biomass burning emits significant quantities of intermediate-volatility and semi-volatile volatile organic compounds (I/SVOCs) in a complex mixture, probably containing many thousands of chemical species. These components are significantly more toxic and have poorly understood chemistry compared to volatile organic compounds routinely analysed in ambient air, however quantification of I/SVOCs presents a difficult analytical challenge. The gases and particles emitted during the test combustion of a range of domestic solid fuels collected from across New Delhi were sampled and analysed. Organic aerosol was collected onto Teflon (PTFE) filters and residual low-volatility gases were adsorbed to the surface of solid-phase extraction (SPE) disks. A new method relying on accelerated solvent extraction ASE) coupled to comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC×GC-ToF-MS) was developed. This highly sensitive and powerful analytical technique enabled over 3000 peaks from I/SVOC species with unique mass spectra to be detected. 15-100% of gas-phase emissions and 7-100% of particle-phase emissions were characterised. The method was analysed for suitability to make quantitative measurements of I/SVOCs using SPE disks. Analysis of SPE disks indicated phenolic and furanic compounds were important to gas-phase I/SVOC emissions and levoglucosan to the aerosol phase. Gasand particle-phase emission factors for 21 polycyclic aromatic hydrocarbons (PAHs) were derived, including 16 compounds listed by the US EPA as priority pollutants. Gas-phase emissions were dominated by smaller PAHs. New emission factors were measured (mg kg-1) for PAHs from combustion of cow dung cake (615), municipal solid waste (1022), crop residue 747), sawdust (1236), fuel wood (247), charcoal (151) and liquified petroleum gas (56). The results of this study indicate that cow dung cake and municipal solid waste burning are likely to be significant PAH sources and further study is required to quantify their impact, alongside emissions from fuel wood burning. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
64. Observations of speciated isoprene nitrates in Beijing: implications for isoprene chemistry.
- Author
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Reeves, Claire E., Mills, Graham P., Whalley, Lisa K., Acton, W. Joe F., Bloss, William J., Crilley, Leigh R., Grimmond, Sue, Heard, Dwayne E., Hewitt, C. Nicholas, Hopkins, James R., Kotthaus, Simone, Kramer, Louisa J., Jones, Roderic L., Lee, James D., Yanhui Liu, Bin Ouyang, Slater, Eloise, Squires, Freya, Xinming Wang, and Woodward-Massey, Robert
- Abstract
Isoprene is the most important biogenic volatile organic compound in the atmosphere. Its calculated impact on ozone (O
3 ) is critically dependent on the model isoprene oxidation chemical scheme, in particular the way the isoprene-derived nitrates (IN) are treated. By combining gas chromatography with mass spectrometry, we have developed a system capable of separating, and unambiguously measuring, individual IN isomers. In this paper we report measurements from its first field deployment, which took place in Beijing as part of the Atmospheric Pollution and Human Health in a Chinese Megacity (APHH-Beijing) programme, along with box model simulations using the Master Chemical Mechanism (MCM) (v.3.3.1) to assess the key processes affecting the production and loss of the IN. Seven individual isoprene nitrates were identified and quantified during the summer campaign: two β-isoprene hydroxy nitrates (IHN); four δ isoprene carbonyl nitrates (ICN); and propanone nitrate. Whilst we had previously demonstrated that the system can measure the four δ-IHN, we found no evidence of them in Beijing. The two β-IHN mixing ratios are well correlated with an R² value of 0.85. The mean for their ratio ((1-OH, 2-ONO2 )-IHN : (4-OH, 3-ONO2 )-IHN) is 3.4 and exhibits no clear diel cycle (the numbers in the names indicate the carbon (C) atom in the isoprene chain to which the radical is added). Examining this in a box model demonstrates its sensitivity to nitric oxide (NO), with lower NO mixing ratios favouring (1-OH, 2-ONO2 )-IHN over (4-OH, 3-ONO2 )-IHN. This is largely a reflection of the modelled ratios of their respective precursor peroxy radicals which, at NO mixing ratios of less than 1 part per billion (ppb), increase substantially with decreasing NO. Interestingly, this ratio in the peroxy radicals still exceeds the kinetic ratio (i.e. their initial ratio based on the yields of the adducts from OH addition to isoprene and the rates of reaction of the adducts with oxygen (O2 )) even at NO mixing ratios as high as 100 ppb. The relationship of the observed β-IHN ratio with NO is much weaker than modelled, partly due to far fewer data points, but it agrees with the model simulation in so far as there tend to be larger ratios at sub 1 ppb amounts of NO. Of the δ-ICN, the two trans (E) isomers are observed to have the highest mixing ratios and the mean isomer ratio (E-(4-ONO2 , 1-CO)-ICN to E-(1-ONO2 , 4-CO)-ICN)) is 1.4, which is considerably lower than the expected ratio of 6 for addition of NO3 in the C1 and C4 carbon positions in the isoprene chain. The MCM produces far more δ-ICN than observed, particularly at night and it also simulates an increase in the daytime δ-ICN that greatly exceeds that seen in the observations. Interestingly, the modelled source of δ-ICN is predominantly during the daytime, due to the presence in Beijing of appreciable daytime amounts of NO3 along with isoprene. The modelled ratios of δ-ICN to propanone nitrate are very different to the observed. This study demonstrates the value of speciated IN measurements to test our understanding of the isoprene degradation chemistry. Our interpretation is limited by the uncertainties in our measurements and relatively small data set, but highlights areas of the isoprene chemistry that warrant further study, in particular the NO3 initiated isoprene degradation chemistry. [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
- View/download PDF
65. Isoprene emission potentials from European oak forests derived from canopy flux measurements: an assessment of uncertainties and inter-algorithm variability
- Author
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Langford, Ben, primary, Cash, James, additional, Acton, W. Joe F., additional, Valach, Amy C., additional, Hewitt, C. Nicholas, additional, Fares, Silvano, additional, Goded, Ignacio, additional, Gruening, Carsten, additional, House, Emily, additional, Kalogridis, Athina-Cerise, additional, Gros, Valérie, additional, Schafers, Richard, additional, Thomas, Rick, additional, Broadmeadow, Mark, additional, and Nemitz, Eiko, additional
- Published
- 2017
- Full Text
- View/download PDF
66. Isoprene emission potentials from European oak forests derived from canopy flux measurements:An assessment of uncertainties and inter-algorithm variability
- Author
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Langford, Ben, Cash, James, Acton, W. Joe F., Valach, Amy C., Hewitt, C. Nicholas, Fares, Silvano, Goded, Ignacio, Gruening, Carsten, House, Emily, Kalogridis, Athina-Cerise, Gros, Valérie, Schafers, Richard, Thomas, Rick, Broadmeadow, Mark, Nemitz, Eiko, Langford, Ben, Cash, James, Acton, W. Joe F., Valach, Amy C., Hewitt, C. Nicholas, Fares, Silvano, Goded, Ignacio, Gruening, Carsten, House, Emily, Kalogridis, Athina-Cerise, Gros, Valérie, Schafers, Richard, Thomas, Rick, Broadmeadow, Mark, and Nemitz, Eiko
- Published
- 2017
67. Isoprene emission potentials from European oak forests derived from canopy flux measurements: an assessment of uncertainties and inter-algorithm variability
- Author
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Langford, Ben, Cash, James, Acton, W. Joe F., Valach, Amy C., Hewitt, C. Nicholas, Fares, Silvano, Goded, Ignacio, Gruening, Carsten, House, Emily, Kalogridis, Athina-Cerise, Gros, Valérie, Schafers, Richard, Thomas, Rick, Broadmeadow, Mark, Nemitz, Eiko, Langford, Ben, Cash, James, Acton, W. Joe F., Valach, Amy C., Hewitt, C. Nicholas, Fares, Silvano, Goded, Ignacio, Gruening, Carsten, House, Emily, Kalogridis, Athina-Cerise, Gros, Valérie, Schafers, Richard, Thomas, Rick, Broadmeadow, Mark, and Nemitz, Eiko
- Abstract
Biogenic emission algorithms predict that oak forests account for ∼ 70 % of the total European isoprene budget. Yet the isoprene emission potentials (IEPs) that underpin these model estimates are calculated from a very limited number of leaf-level observations and hence are highly uncertain. Increasingly, micrometeorological techniques such as eddy covariance are used to measure whole-canopy fluxes directly, from which isoprene emission potentials can be calculated. Here, we review five observational datasets of isoprene fluxes from a range of oak forests in the UK, Italy and France. We outline procedures to correct the measured net fluxes for losses from deposition and chemical flux divergence, which were found to be on the order of 5–8 and 4–5 %, respectively. The corrected observational data were used to derive isoprene emission potentials at each site in a two-step process. Firstly, six commonly used emission algorithms were inverted to back out time series of isoprene emission potential, and then an “average” isoprene emission potential was calculated for each site with an associated uncertainty. We used these data to assess how the derived emission potentials change depending upon the specific emission algorithm used and, importantly, on the particular approach adopted to derive an average site-specific emission potential. Our results show that isoprene emission potentials can vary by up to a factor of 4 depending on the specific algorithm used and whether or not it is used in a “big-leaf” or “canopy environment (CE) model” format. When using the same algorithm, the calculated average isoprene emission potential was found to vary by as much as 34 % depending on how the average was derived. Using a consistent approach with version 2.1 of the Model for Emissions of Gases and Aerosols from Nature (MEGAN), we derive new ecosystem-scale isoprene emission potentials for the five measurement sites: Alice Holt, UK (10 500 ± 2500 µg m−2 h−1); Bosco Fontana, Italy (1610
- Published
- 2017
68. Supplementary material to "Isoprene emission potentials from European oak forests derived from canopy flux measurements: An assessment of uncertainties and inter-algorithm variability"
- Author
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Langford, Ben, primary, Cash, James, additional, Acton, W. Joe F., additional, Valach, Amy C., additional, Hewitt, C. Nicholas, additional, Fares, Silvano, additional, Goded, Ignacio, additional, Gruening, Carsten, additional, House, Emily, additional, Kalogridis, Athina-Cerise, additional, Gros, Valérie, additional, Schafers, Richard, additional, Thomas, Rick, additional, Broadmeadow, Mark, additional, and Nemitz, Eiko, additional
- Published
- 2017
- Full Text
- View/download PDF
69. Canopy-scale flux measurements and bottom-up emission estimates of volatile organic compounds from a mixed oak and hornbeam forest in northern Italy
- Author
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Acton, W. Joe. F, Schallhart, Simon, Langford, Ben, Valach, Amy, Rantala, Pekka, Fares, Silvano, Carriero, Giulia, Tillmann, Ralf, Tomlinson, Sam J., Dragosits, Ulrike, Gianelle, Damiano, Hewitt, C. Nicholas, Nemitz, Eiko, Acton, W. Joe. F, Schallhart, Simon, Langford, Ben, Valach, Amy, Rantala, Pekka, Fares, Silvano, Carriero, Giulia, Tillmann, Ralf, Tomlinson, Sam J., Dragosits, Ulrike, Gianelle, Damiano, Hewitt, C. Nicholas, and Nemitz, Eiko
- Abstract
This paper reports the fluxes and mixing ratios of biogenically emitted volatile organic compounds (BVOCs) 4 m above a mixed oak and hornbeam forest in northern Italy. Fluxes of methanol, acetaldehyde, isoprene, methyl vinyl ketone + methacrolein, methyl ethyl ketone and monoterpenes were obtained using both a proton-transfer-reaction mass spectrometer (PTR-MS) and a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) together with the methods of virtual disjunct eddy covariance (using PTR-MS) and eddy covariance (using PTR-ToF-MS). Isoprene was the dominant emitted compound with a mean daytime flux of 1.9 mg m−2 h−1. Mixing ratios, recorded 4 m above the canopy, were dominated by methanol with a mean value of 6.2 ppbv over the 28-day measurement period. Comparison of isoprene fluxes calculated using the PTR-MS and PTR-ToF-MS showed very good agreement while comparison of the monoterpene fluxes suggested a slight over estimation of the flux by the PTR-MS. A basal isoprene emission rate for the forest of 1.7 mg m−2 h−1 was calculated using the Model of Emissions of Gases and Aerosols from Nature (MEGAN) isoprene emission algorithms (Guenther et al., 2006). A detailed tree-species distribution map for the site enabled the leaf-level emission of isoprene and monoterpenes recorded using gas-chromatography mass spectrometry (GC–MS) to be scaled up to produce a bottom-up canopy-scale flux. This was compared with the top-down canopy-scale flux obtained by measurements. For monoterpenes, the two estimates were closely correlated and this correlation improved when the plant-species composition in the individual flux footprint was taken into account. However, the bottom-up approach significantly underestimated the isoprene flux, compared with the top-down measurements, suggesting that the leaf-level measurements were not representative of actual emission rates.
- Published
- 2016
70. Canopy-scale flux measurements and bottom-up emission estimates of volatile organic compounds from a mixed oak and hornbeam forest in northern Italy
- Author
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Acton, W. Joe F., primary, Schallhart, Simon, additional, Langford, Ben, additional, Valach, Amy, additional, Rantala, Pekka, additional, Fares, Silvano, additional, Carriero, Giulia, additional, Tillmann, Ralf, additional, Tomlinson, Sam J., additional, Dragosits, Ulrike, additional, Gianelle, Damiano, additional, Hewitt, C. Nicholas, additional, and Nemitz, Eiko, additional
- Published
- 2016
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71. Validity and limitations of simple reaction kinetics to calculate concentrations of organic compounds from ion counts in PTR-MS
- Author
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Holzinger, Rupert, Acton, W. Joe F., Bloss, William J., Breitenlechner, Martin, Crilley, Leigh R., Dusanter, Sebastien, Gonin, Marc, Gros, Valerie, Keutsch, Frank N., Kiendler-Scharr, Astrid, Kramer, Louisa J., Krechmer, Jordan E., Languille, Baptiste, Locoge, Nadine, Lopez-Hilfiker, Felipe, Materic, Dusan, Moreno, Sergi, Nemitz, Eiko, Quelever, Lauriane L. J., Esteve, Roland Sarda, Sauvage, Stephane, Schallhart, Simon, Sommariva, Roberto, Tillmann, Ralf, Wedel, Sergej, Worton, David R., Xu, Kangming, Zaytsev, Alexander, Sub Atmospheric physics and chemistry, Marine and Atmospheric Research, INAR Physics, Polar and arctic atmospheric research (PANDA), Sub Atmospheric physics and chemistry, Marine and Atmospheric Research, University of Birmingham, Institut für Ionenphysik und Angewandte Physik - Institute for Ion Physics and Applied Physics [Innsbruck], Leopold Franzens Universität Innsbruck - University of Innsbruck, Centre for Energy and Environment (CERI EE - IMT Nord Europe), Ecole nationale supérieure Mines-Télécom Lille Douai (IMT Nord Europe), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), Tofwerk AG, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Chimie Atmosphérique Expérimentale (CAE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Centre for Energy and Environment (CERI EE), Ecole nationale supérieure Mines-Télécom Lille Douai (IMT Lille Douai), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), and Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)
- Subjects
Atmospheric Science ,Materials science ,010504 meteorology & atmospheric sciences ,Proton ,Hydronium ,H3O+ ,TRACE GASES ,Analytical chemistry ,010501 environmental sciences ,01 natural sciences ,114 Physical sciences ,Atmospheric Sciences ,Ion ,Chemical kinetics ,chemistry.chemical_compound ,Reaction rate constant ,RATE CONSTANTS ,Calibration ,ddc:550 ,lcsh:TA170-171 ,ComputingMilieux_MISCELLANEOUS ,0105 earth and related environmental sciences ,[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere ,CALIBRATION ,Range (particle radiation) ,lcsh:TA715-787 ,AIR ,lcsh:Earthwork. Foundations ,010401 analytical chemistry ,lcsh:Environmental engineering ,0104 chemical sciences ,Trace gas ,chemistry ,[SDU]Sciences of the Universe [physics] ,TOF-MS ,REACTION MASS-SPECTROMETRY ,SENSITIVITY - Abstract
In September 2017, we conducted a proton-transfer-reaction mass-spectrometry (PTR-MS) intercomparison campaign at the CESAR observatory, a rural site in the central Netherlands near the village of Cabauw. Nine research groups deployed a total of 11 instruments covering a wide range of instrument types and performance. We applied a new calibration method based on fast injection of a gas standard through a sample loop. This approach allows calibrations on timescales of seconds, and within a few minutes an automated sequence can be run allowing one to retrieve diagnostic parameters that indicate the performance status. We developed a method to retrieve the mass-dependent transmission from the fast calibrations, which is an essential characteristic of PTR-MS instruments, limiting the potential to calculate concentrations based on counting statistics and simple reaction kinetics in the reactor/drift tube. Our measurements show that PTR-MS instruments follow the simple reaction kinetics if operated in the standard range for pressures and temperature of the reaction chamber (i.e. 1–4 mbar, 30–120∘, respectively), as well as a reduced field strength E∕N in the range of 100–160 Td. If artefacts can be ruled out, it becomes possible to quantify the signals of uncalibrated organics with accuracies better than ±30 %. The simple reaction kinetics approach produces less accurate results at E∕N levels below 100 Td, because significant fractions of primary ions form water hydronium clusters. Deprotonation through reactive collisions of protonated organics with water molecules needs to be considered when the collision energy is a substantial fraction of the exoergicity of the proton transfer reaction and/or if protonated organics undergo many collisions with water molecules.
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72. Extreme Concentrations of Nitric Oxide Control Daytime Oxidation and Quench Nocturnal Oxidation Chemistry in Delhi during Highly Polluted Episodes.
- Author
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Nelson BS, Bryant DJ, Alam MS, Sommariva R, Bloss WJ, Newland MJ, Drysdale WS, Vaughan AR, Acton WJF, Hewitt CN, Crilley LR, Swift SJ, Edwards PM, Lewis AC, Langford B, Nemitz E, Shivani, Gadi R, Gurjar BR, Heard DE, Whalley LK, Şahin ÜA, Beddows DCS, Hopkins JR, Lee JD, Rickard AR, and Hamilton JF
- Abstract
Delhi, India, suffers from periods of very poor air quality, but little is known about the chemical production of secondary pollutants in this highly polluted environment. During the postmonsoon period in 2018, extremely high nighttime concentrations of NO
x (NO and NO2 ) and volatile organic compounds (VOCs) were observed, with median NOx mixing ratios of ∼200 ppbV (maximum of ∼700 ppbV). A detailed chemical box model constrained to a comprehensive suite of speciated VOC and NOx measurements revealed very low nighttime concentrations of oxidants, NO3 , O3 , and OH, driven by high nighttime NO concentrations. This results in an atypical NO3 diel profile, not previously reported in other highly polluted urban environments, significantly perturbing nighttime radical oxidation chemistry. Low concentrations of oxidants and high nocturnal primary emissions coupled with a shallow boundary layer led to enhanced early morning photo-oxidation chemistry. This results in a temporal shift in peak O3 concentrations when compared to the premonsoon period (12:00 and 15:00 local time, respectively). This shift will likely have important implications on local air quality, and effective urban air quality management should consider the impacts of nighttime emission sources during the postmonsoon period., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)- Published
- 2023
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73. Sources of non-methane hydrocarbons in surface air in Delhi, India.
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Stewart GJ, Nelson BS, Drysdale WS, Acton WJF, Vaughan AR, Hopkins JR, Dunmore RE, Hewitt CN, Nemitz E, Mullinger N, Langford B, Shivani, Reyes-Villegas E, Gadi R, Rickard AR, Lee JD, and Hamilton JF
- Abstract
Rapid economic growth and development have exacerbated air quality problems across India, driven by many poorly understood pollution sources and understanding their relative importance remains critical to characterising the key drivers of air pollution. A comprehensive suite of measurements of 90 non-methane hydrocarbons (NMHCs) (C
2 -C14 ), including 12 speciated monoterpenes and higher molecular weight monoaromatics, were made at an urban site in Old Delhi during the pre-monsoon (28-May to 05-Jun 2018) and post-monsoon (11 to 27-Oct 2018) seasons using dual-channel gas chromatography (DC-GC-FID) and two-dimensional gas chromatography (GC×GC-FID). Significantly higher mixing ratios of NMHCs were measured during the post-monsoon campaign, with a mean night-time enhancement of around 6. Like with NOx and CO, strong diurnal profiles were observed for all NMHCs, except isoprene, with very high NMHC mixing ratios between 35-1485 ppbv. The sum of mixing ratios of benzene, toluene, ethylbenzene and xylenes (BTEX) routinely exceeded 100 ppbv at night during the post-monsoon period, with a maximum measured mixing ratio of monoaromatic species of 370 ppbv. The mixing ratio of highly reactive monoterpenes peaked at around 6 ppbv in the post-monsoon campaign and correlated strongly with anthropogenic NMHCs, suggesting a strong non-biogenic source in Delhi. A detailed source apportionment study was conducted which included regression analysis to CO, acetylene and other NMHCs, hierarchical cluster analysis, EPA UNMIX 6.0, principal component analysis/absolute principal component scores (PCA/APCS) and comparison with NMHC ratios (benzene/toluene and i-/n-pentane) in ambient samples to liquid and solid fuels. These analyses suggested the primary source of anthropogenic NMHCs in Delhi was from traffic emissions (petrol and diesel), with average mixing ratio contributions from Unmix and PCA/APCS models of 38% from petrol, 14% from diesel and 32% from liquified petroleum gas (LPG) with a smaller contribution (16%) from solid fuel combustion. Detailed consideration of the underlying meteorology during the campaigns showed that the extreme night-time mixing ratios of NMHCs during the post-monsoon campaign were the result of emissions into a very shallow and stagnant boundary layer. The results of this study suggest that despite widespread open burning in India, traffic-related petrol and diesel emissions remain the key drivers of gas-phase urban air pollution in Delhi.- Published
- 2021
- Full Text
- View/download PDF
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