Capability of CI-Orbitrap for Gas-Phase Analysis in Atmospheric Chemistry: A Comparison with the CI-APi-TOF Technique

Chemisorption of ethylene was studied on thin polycrystalline layers of nickel prepared by metal deposition in high vacuum and modified by preadsorbed oxygen. The volumetric method combined with the gas-phase analysis and the measurement of the electrical resistance changes of these layers were used. Already small amounts of preadsorbed oxygen of the order of 10-2 of the monolayer affect rather substantially the extent of ethylene chemisorption. The extent of the initial irreversible chemisorption and also the total adsorption of ethylene as a function of the amount of preadsorbed oxygen have a maximum at the surface oxygen concentration of 3 . 1013 molecule cm-2. The adsorption accompanied by the extensive dissociation of ethylene C-H bonds proceeds predominantly on nickel atoms with lower coordination (atoms on the microcrystal edges, corner atoms, etc.), where also oxygen chemisorption proceeds preferentially.

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Application of random forest regression to the calculation of gas-phase chemistry within the GEOS-Chem chemistry model v10

Geoscientific Model Development ◽

10.5194/gmd-12-1209-2019 ◽

2019 ◽

Vol 12 (3) ◽

pp. 1209-1225 ◽

Cited By ~ 15

Author(s):

Christoph A. Keller ◽

Mat J. Evans

Keyword(s):

Machine Learning ◽

Random Forest ◽

Gas Phase ◽

Atmospheric Chemistry ◽

Random Forest Regression ◽

Data Set ◽

Gas Phase Chemistry ◽

Chemical Conditions ◽

Phase Chemistry ◽

The Impact

Abstract. Atmospheric chemistry models are a central tool to study the impact of chemical constituents on the environment, vegetation and human health. These models are numerically intense, and previous attempts to reduce the numerical cost of chemistry solvers have not delivered transformative change. We show here the potential of a machine learning (in this case random forest regression) replacement for the gas-phase chemistry in atmospheric chemistry transport models. Our training data consist of 1 month (July 2013) of output of chemical conditions together with the model physical state, produced from the GEOS-Chem chemistry model v10. From this data set we train random forest regression models to predict the concentration of each transported species after the integrator, based on the physical and chemical conditions before the integrator. The choice of prediction type has a strong impact on the skill of the regression model. We find best results from predicting the change in concentration for long-lived species and the absolute concentration for short-lived species. We also find improvements from a simple implementation of chemical families (NOx = NO + NO2). We then implement the trained random forest predictors back into GEOS-Chem to replace the numerical integrator. The machine-learning-driven GEOS-Chem model compares well to the standard simulation. For ozone (O3), errors from using the random forests (compared to the reference simulation) grow slowly and after 5 days the normalized mean bias (NMB), root mean square error (RMSE) and R2 are 4.2 %, 35 % and 0.9, respectively; after 30 days the errors increase to 13 %, 67 % and 0.75, respectively. The biases become largest in remote areas such as the tropical Pacific where errors in the chemistry can accumulate with little balancing influence from emissions or deposition. Over polluted regions the model error is less than 10 % and has significant fidelity in following the time series of the full model. Modelled NOx shows similar features, with the most significant errors occurring in remote locations far from recent emissions. For other species such as inorganic bromine species and short-lived nitrogen species, errors become large, with NMB, RMSE and R2 reaching >2100 % >400 % and <0.1, respectively. This proof-of-concept implementation takes 1.8 times more time than the direct integration of the differential equations, but optimization and software engineering should allow substantial increases in speed. We discuss potential improvements in the implementation, some of its advantages from both a software and hardware perspective, its limitations, and its applicability to operational air quality activities.

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Atmospheric chemistry of trans-CF3CHCHCl: Kinetics of the gas-phase reactions with Cl atoms, OH radicals, and O3

Journal of Photochemistry and Photobiology A Chemistry ◽

10.1016/j.jphotochem.2008.05.013 ◽

2008 ◽

Vol 199 (1) ◽

pp. 92-97 ◽

Cited By ~ 35

Author(s):

M.P. Sulbaek Andersen ◽

E.J.K. Nilsson ◽

O.J. Nielsen ◽

M.S. Johnson ◽

M.D. Hurley ◽

...

Keyword(s):

Gas Phase ◽

Atmospheric Chemistry ◽

Oh Radicals ◽

Gas Phase Reactions ◽

Kinetics Of ◽

Cl Atoms

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Four-wave mixing of picosecond pulses in hollow fibers: expanding the possibilities of gas-phase analysis

Applied Physics B ◽

10.1007/s003400100555 ◽

2001 ◽

Vol 72 (5) ◽

pp. 575-582 ◽

Cited By ~ 34

Author(s):

A.B. Fedotov ◽

F. Giammanco ◽

A.N. Naumov ◽

P. Marsili ◽

A. Ruffini ◽

...

Keyword(s):

Gas Phase ◽

Phase Analysis ◽

Four Wave Mixing ◽

Hollow Fibers ◽

Wave Mixing ◽

Picosecond Pulses

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Newly developed instrumentation for measuring highly oxidized molecules at atmospheric pressure

10.5194/egusphere-egu21-12911 ◽

2021 ◽

Author(s):

Paap Koemets ◽

Sander Mirme ◽

Kuno Kooser ◽

Heikki Junninen

Keyword(s):

Gas Phase ◽

Atmospheric Chemistry ◽

Atmospheric Pressure ◽

Chemical Ionization ◽

Measurement Technology ◽

Differential Mobility Analyzer ◽

Neutral Cluster ◽

Differential Mobility ◽

Alpha Pinene ◽

Ambient Measurements

The Highly Oxidized Molecule Ion Spectrometer (HOMIS) is a novel instrument for measuring the total concentration of highly oxidized molecules (HOM-s) (Bianchi et al., 2019) at atmospheric pressure. The device combines a chemical ionization charger with a multi-channel differential mobility analyzer. The chemical ionization charger is based on the principles outlined by Eisele and Tanner (1993). The charger is attached to a parallel differential mobility analyzer identical to the ones used in the Neutral cluster and Air Ion Spectrometer (NAIS, Mirme 2011), but with modified sample and sheath air flow rates to improve the mobility resolution of the device. The complete mobility distribution in the range from 3.2 to 0.056 cm2/V/s is measured simultaneously by 25 electrometers. The range captures the charger ions, monomers, dimers, trimers but also extends far towards larger particles to possibly detect larger HOM-s that have not been measured with existing instrumentation. The maximum time resolution of the device is 1 second allowing it to detect rapid changes in the sample. The device has been designed to be easy to use, require little maintenance and work reliably in various environments during long term measurements.First results of the prototype were acquired from laboratory experiments and ambient measurements. Experiments were conducted at the Laboratory of Environmental Physics, University of Tartu. The sample was drawn from a reaction chamber where alpha-pinene and ozone were introduced. Initial results show a good response when concentrations of alpha-pinene and ozone were changed.&#160;Ambient measurements were conducted at the SMEAR Estonia measurement station in a hemiboreal forest for 10 days in the spring and two months in the winter of 2020. The HOMIS measurements were performed together with a CI-APi-TOF (Jokinen et al., 2012).&#160;References:Bianchi, F., Kurt&#233;n, T., Riva, M., Mohr, C., Rissanen, M. P., Roldin, P., Berndt, T., Crounse, J. D., Wennberg, P. O., Mentel, T. F., Wildt, J., Junninen, H., Jokinen, T., Kulmala, M., Worsnop, D. R., Thornton, J. A., Donahue, N., Kjaergaard, H. G. and Ehn, M. (2019), &#8220;Highly Oxygenated Organic Molecules (HOM) from Gas-Phase Autoxidation Involving Peroxy Radicals: A Key Contributor to Atmospheric Aerosol&#8221;, Chemical Reviews, 119, 6, 3472&#8211;3509Eisele, F. L., Tanner D. J. (1993), &#8220;Measurement of the gas phase concentration of H2SO4 and methane sulfonic acid and estimates of H2SO4 production and loss in the atmosphere&#8221;, JGR: Atmospheres, 98, 9001-9010Jokinen T., Sipil&#228; M., Junninen H., Ehn M., L&#246;nn G., Hakala J., Pet&#228;j&#228; T., Mauldin III R. L., Kulmala M., and Worsnop D. R. (2012), &#8220;Atmospheric sulphuric acid and neutral cluster measurements using CI-APi-TOF&#8221;, Atmospheric Chemistry and Physics, 12, 4117&#8211;4125Mirme, S. (2011), &#8220;Development of nanometer aerosol measurement technology&#8221;, Doctoral thesis, University of Tartu

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Evaluated kinetic and photochemical data for atmospheric chemistry: Volume II – reactions of organic species

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-5-6295-2005 ◽

2005 ◽

Vol 5 (4) ◽

pp. 6295-7168 ◽

Cited By ~ 18

Author(s):

R. Atkinson ◽

D. L. Baulch ◽

R. A. Cox ◽

J. N. Crowley ◽

R. F. Hampson ◽

...

Keyword(s):

Kinetic Parameters ◽

Gas Phase ◽

Atmospheric Chemistry ◽

Kinetic Data ◽

Photochemical Reactions ◽

Data Evaluation ◽

Organic Species ◽

Summary Sheet

Abstract. This article, the second in the series, presents kinetic and photochemical data evaluated by the IUPAC Subcommittee on Gas Kinetic Data Evaluation for Atmospheric Chemistry. It covers the gas phase and photochemical reactions of Organic species, which were last published in 1999, and were updated on the IUPAC website in late 2002. The article consists of a summary sheet, containing the recommended kinetic parameters for the evaluated reactions, and eight appendices containing the data sheets, which provide information upon which the recommendations are made.

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Basicity of Amines in the Gas Phase – Analysis of the Base-Strengthening Effect of anN-Trityl Group by Use of a Triadic Formula

European Journal of Organic Chemistry ◽

10.1002/ejoc.200500994 ◽

2006 ◽

Vol 2006 (11) ◽

pp. 2581-2589 ◽

Cited By ~ 7

Author(s):

Robert Vianello ◽

Howard Maskill ◽

Zvonimir B. Maksić

Keyword(s):

Gas Phase ◽

Phase Analysis ◽

Strengthening Effect

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The role of platinum on the NOx storage and desorption behavior of ceria: An online FT-IR study combined with in situ Raman and UV-Vis spectroscopy

Physical Chemistry Chemical Physics ◽

10.1039/d0cp05800a ◽

2020 ◽

Author(s):

Anastasia Filtschew ◽

Pablo Beato ◽

Søren Birk Rasmussen ◽

Christian Hess

Keyword(s):

Gas Phase ◽

Phase Analysis ◽

Room Temperature ◽

Storage Mechanism ◽

In Situ Raman ◽

Vis Spectroscopy ◽

Ft Ir ◽

Ir Study

The role of platinum on the room temperature NOx storage mechanism and the NOx desorption behavior of ceria was investigated by combining online FT-IR gas-phase analysis with in situ Raman...

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Do organic surface films on sea salt aerosols influence atmospheric chemistry? – a model study

Atmospheric Chemistry and Physics ◽

10.5194/acp-7-5555-2007 ◽

2007 ◽

Vol 7 (21) ◽

pp. 5555-5567 ◽

Cited By ~ 27

Author(s):

L. Smoydzin ◽

R. von Glasow

Keyword(s):

Mass Transfer ◽

Liquid Phase ◽

Gas Phase ◽

Aqueous Phase ◽

Atmospheric Chemistry ◽

Organic Coating ◽

Sea Salt ◽

Tropospheric Chemistry ◽

Special Focus ◽

Sea Salt Aerosols

Abstract. Organic material from the ocean's surface can be incorporated into sea salt aerosol particles often producing a surface film on the aerosol. Such an organic coating can reduce the mass transfer between the gas phase and the aerosol phase influencing sea salt chemistry in the marine atmosphere. To investigate these effects and their importance for the marine boundary layer (MBL) we used the one-dimensional numerical model MISTRA. We considered the uncertainties regarding the magnitude of uptake reduction, the concentrations of organic compounds in sea salt aerosols and the oxidation rate of the organics to analyse the possible influence of organic surfactants on gas and liquid phase chemistry with a special focus on halogen chemistry. By assuming destruction rates for the organic coating based on laboratory measurements we get a rapid destruction of the organic monolayer within the first meters of the MBL. Larger organic initial concentrations lead to a longer lifetime of the coating but lead also to an unrealistically strong decrease of O3 concentrations as the organic film is destroyed by reaction with O3. The lifetime of the film is increased by assuming smaller reactive uptake coefficients for O3 or by assuming that a part of the organic surfactants react with OH. With regard to tropospheric chemistry we found that gas phase concentrations for chlorine and bromine species decreased due to the decreased mass transfer between gas phase and aerosol phase. Aqueous phase chlorine concentrations also decreased but aqueous phase bromine concentrations increased. Differences for gas phase concentrations are in general smaller than for liquid phase concentrations. The effect on gas phase NO2 or NO is very small (reduction less than 5%) whereas liquid phase NO2 concentrations increased in some cases by nearly 100%. We list suggestions for further laboratory studies which are needed for improved model studies.

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