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Mariano A. Teruel - One of the best experts on this subject based on the ideXlab platform.
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Atmospheric Sink of β-ocimene and camphene initiated by Cl atoms: kinetics and products at NOx free-air
RSC Advances, 2018Co-Authors: Elizabeth Gaona-colmán, María B. Blanco, Ian Barnes, Peter Wiesen, Mariano A. TeruelAbstract:Rate coefficients for the gas-phase reactions of Cl atoms with β-ocimene and camphene were determined to be (in units of 10−10 cm3 per molecule per s) 5.5 ± 0.7 and 3.3 ± 0.4, respectively. The experiments were performed by the relative technique in an environmental chamber with FTIR detection of the reactants at 298 K and 760 torr. Product identification experiments were carried out by gas chromatography with mass spectrometry detection (GC-MS) using the solid-phase microextraction (SPME) method employing on-fiber carbonyl compound derivatization with o-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine hydrochloride. An analysis of the available rates of addition of Cl atoms and OH radicals to the double bond of alkenes and cyclic and acyclic terpenes with a conjugated double bond at 298 K is presented. The Atmospheric persistence of these compounds was calculated taking into account the measured rate coefficients. In addition, tropospheric chemical mechanisms for the title reactions are postulated.
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Atmospheric Sink of methyl chlorodifluoroacetate and ethyl chlorodifluoroacetate temperature dependent rate coefficients product distribution of their reactions with cl atoms and cf2clc o oh formation
RSC Advances, 2016Co-Authors: María B. Blanco, Ian Barnes, Peter Wiesen, Mariano A. TeruelAbstract:Rate coefficients as a function of temperature have been measured for the first time for the gas-phase reactions of chlorine atoms with methyl chlorodifluoracetate (k1) and ethyl chlorodifluoroacetate (k2) using the relative rate technique. The experiments were carried out in a 1080 L photoreactor over the temperature range 287–313 K at a total pressure of 1000 ± 10 mbar of synthetic air using in situ FTIR spectroscopy to monitor reactants and products. The following Arrhenius expressions were obtained: k(MCDFA+Cl) = (9.6 ± 5.1) × 10−12 exp[−(1363 ± 79)/T] and k(ECDFA+Cl) = (64.4 ± 29.7) × 10−12 exp[−(1110 ± 68)/T]. The kinetic results are compared with previous experimental and theoretical studies. In addition, a product study of the reactions of Cl with methyl chlorodifluoracetate and ethyl chlorodifluoroacetate is reported. The results indicate that in the absence of NOx the main fate of the alkoxy radicals formed after H-atom abstraction by Cl from the –CH3 group in methyl chlorodifluoroacetate is reaction of the radical with O2 to form the mixed anhydride CF2ClC(O)OC(O)H. In the case of ethyl chlorodifluoroacetate the main fate of the alkoxy formed via H-atom abstraction by Cl from the –CH2– entity in the ethyl group is α-ester rearrangement to produce chlorodifluoroacetic acid and the corresponding radical. The yields of chlorofluoracetic acid (CF2ClC(O)OH) obtained were as follows: (34 ± 5)% and (86 ± 8)% for the reactions of Cl with CF2ClC(O)OCH3 and CF2ClC(O)OCH2CH3, respectively. The measured yields are rationalized in terms of mechanisms consisting of competitive reaction channels for the formed products in the oxidation, i.e. reaction with O2, α-ester rearrangement and a decomposition pathway. Atmospheric implications are discussed according to the rate coefficients obtained as a function of temperature and altitude, and regarding the formation of chlorofluorocarboxylic acid.
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Atmospheric Sink of methyl chlorodifluoroacetate and ethyl chlorodifluoroacetate: temperature dependent rate coefficients, product distribution of their reactions with Cl atoms and CF2ClC(O)OH formation
RSC Advances, 2016Co-Authors: María B. Blanco, Ian Barnes, Peter Wiesen, Mariano A. TeruelAbstract:Rate coefficients as a function of temperature and product distribution studies have been performed for the first time for the gas-phase reactions of chlorine atoms with methyl chlorodifluoracetate (k1) and ethyl chlorodifluoroacetate (k2) using the relative rate technique.
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Atmospheric Sink of (E)-3-Hexen-1-ol, (Z)-3-Hepten-1-ol, and (Z)-3-Octen-1-ol: Rate Coefficients and Mechanisms of the OH-Radical Initiated Degradation.
Environmental science & technology, 2015Co-Authors: Rodrigo G. Gibilisco, María B. Blanco, Ian Barnes, Peter Wiesen, Iustinian Bejan, Mariano A. TeruelAbstract:A kinetic study of the gas-phase reactions of OH radicals with three unsaturated biogenic alcohols, (E)-3-hexen-1-ol, (Z)-3-hepten-1-ol, and (Z)-3-octen-1-ol, has been performed. The rate coefficients obtained are (in units of 10(-10) cm(3) molecule(-1) s(-1)) k1 (OH + (E)-CH2(OH)CH2CH═CHCH2CH3) = (1.14 ± 0.14), k2 (OH + (Z)-CH2(OH)CH2CH═CHCH2CH2CH3) = (1.28 ± 0.23), and k3 (OH + (Z)-CH2(OH)CH2CH═CHCH2CH2CH2CH3) = (1.49 ± 0.35). In addition, a product study on the reactions of OH with (E)-3-hexen-1-ol and (Z)-3-hepten-1-ol is reported. All the experiments were performed at (298 ± 2) K and 1 atm of NOx-free air in a 1080 L photoreactor with in situ FTIR detection of organics. This work constitutes the first kinetic study of the reactions of OH radicals with (Z)-3-hepten-1-ol and (Z)-3-octen-1-ol as well as the first determination of the fate of the hydroxy alkoxy radicals formed in the title reactions. An analysis of the available rates of addition of OH and Cl to the double bond of different unsaturated alcohols at 298 K has shown that they can be related by the expression log kOH = (0.29 ± 0.04) log kCl - 10.8. The Atmospheric lifetimes of the alcohols studies were estimated to be around 1 h for reaction with OH radicals. The products formed in the title reactions are mainly carbonylic compounds that can contribute to the formation of ozone and PANs-type compounds in the troposphere.
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The Cl-initiated oxidation of CH_3C(O)OCH=CH_2, CH_3C(O)OCH_2CH=CH_2, and CH_2=CHC(O)O(CH_2)_3CH_3 in the troposphere
Environmental Science and Pollution Research, 2009Co-Authors: María B. Blanco, Ian Barnes, Peter Wiesen, Iustinian Bejan, Mariano A. TeruelAbstract:Background, aim, and scope Unsaturated esters are emitted to the atmosphere from biogenic and anthropogenic sources, including those from the polymer industry. Little information exists concerning the Atmospheric degradation of unsaturated esters, which are mainly initiated by OH radicals. Limited information is available on the degradation of alkenes by Cl atoms and almost no data exists for the reactions of unsaturated esters with Cl atoms. This data is necessary to assess the impact of such reactions in maritime environments where, under circumstances, OH radical- and Cl atom-initiated oxidation of the compounds can be important. Rate coefficients for the reactions of chlorine atoms with vinyl acetate, allyl acetate, and n -butyl acrylate have been determined at 298 ± 3 K and Atmospheric pressure. The kinetic data have been used in combination with that for structurally similar compounds to infer the kinetic contributions from the possible reaction channels to the overall reaction rate. Materials and methods The decay of the organics was followed using in situ Fourier transform infrared spectroscopy and the rate coefficients were determined using a relative kinetic method and different hydrocarbon reference compounds. Results The following room temperature rate coefficients (in cm^3 molecule^−1 s^−1) were obtained: k _1 (Cl + CH_3C(O)OCH=CH_2) = (2.68 ± 0.91) × 10^−10, k _2 (Cl + CH_3C(O)OCH_2CH=CH_2) = (1.30 ± 0.45) × 10^−10, and k _3 (Cl + CH_2=CHC(O)O(CH_2)_3CH_3) = (2.50 ± 0.78) × 10^−10, where the uncertainties are a combination of the 2 σ statistical errors from linear regression analyses and a contribution to cover uncertainties in the rate coefficients of the reference hydrocarbons. Discussion This is the first kinetic study of the title reactions under Atmospheric conditions. The kinetic data were analyzed in terms of reactivity trends and used to estimate the Atmospheric lifetimes of the esters and assess their potential importance in the marine atmosphere. Conclusions Although reaction with OH radicals is the major Atmospheric Sink for the unsaturated esters studied, reaction with Cl atoms can compete in the early morning hours in coastal areas where the Cl concentration can reach peak values as high as 1 × 10^5 atoms cm^−3. The calculated residence times show that the chemistry of unsaturated esters will impact air quality locally near their emission sources. Recommendations and perspectives The reactions need to be studied over the range of temperatures and pressures generally encountered in the marine atmosphere. In addition, product studies should also be performed as a function of temperature since this will allow degradation mechanisms to be derived, which are representative for the wide range of conditions occurring in marine environments. Inclusion of the kinetic and product data in tropospheric numerical models will allow an assessment of potential environmental impacts of the esters for different marine pollution scenarios.
Ian Barnes - One of the best experts on this subject based on the ideXlab platform.
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Atmospheric Sink of β-ocimene and camphene initiated by Cl atoms: kinetics and products at NOx free-air
RSC Advances, 2018Co-Authors: Elizabeth Gaona-colmán, María B. Blanco, Ian Barnes, Peter Wiesen, Mariano A. TeruelAbstract:Rate coefficients for the gas-phase reactions of Cl atoms with β-ocimene and camphene were determined to be (in units of 10−10 cm3 per molecule per s) 5.5 ± 0.7 and 3.3 ± 0.4, respectively. The experiments were performed by the relative technique in an environmental chamber with FTIR detection of the reactants at 298 K and 760 torr. Product identification experiments were carried out by gas chromatography with mass spectrometry detection (GC-MS) using the solid-phase microextraction (SPME) method employing on-fiber carbonyl compound derivatization with o-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine hydrochloride. An analysis of the available rates of addition of Cl atoms and OH radicals to the double bond of alkenes and cyclic and acyclic terpenes with a conjugated double bond at 298 K is presented. The Atmospheric persistence of these compounds was calculated taking into account the measured rate coefficients. In addition, tropospheric chemical mechanisms for the title reactions are postulated.
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Atmospheric Sink of methyl chlorodifluoroacetate and ethyl chlorodifluoroacetate temperature dependent rate coefficients product distribution of their reactions with cl atoms and cf2clc o oh formation
RSC Advances, 2016Co-Authors: María B. Blanco, Ian Barnes, Peter Wiesen, Mariano A. TeruelAbstract:Rate coefficients as a function of temperature have been measured for the first time for the gas-phase reactions of chlorine atoms with methyl chlorodifluoracetate (k1) and ethyl chlorodifluoroacetate (k2) using the relative rate technique. The experiments were carried out in a 1080 L photoreactor over the temperature range 287–313 K at a total pressure of 1000 ± 10 mbar of synthetic air using in situ FTIR spectroscopy to monitor reactants and products. The following Arrhenius expressions were obtained: k(MCDFA+Cl) = (9.6 ± 5.1) × 10−12 exp[−(1363 ± 79)/T] and k(ECDFA+Cl) = (64.4 ± 29.7) × 10−12 exp[−(1110 ± 68)/T]. The kinetic results are compared with previous experimental and theoretical studies. In addition, a product study of the reactions of Cl with methyl chlorodifluoracetate and ethyl chlorodifluoroacetate is reported. The results indicate that in the absence of NOx the main fate of the alkoxy radicals formed after H-atom abstraction by Cl from the –CH3 group in methyl chlorodifluoroacetate is reaction of the radical with O2 to form the mixed anhydride CF2ClC(O)OC(O)H. In the case of ethyl chlorodifluoroacetate the main fate of the alkoxy formed via H-atom abstraction by Cl from the –CH2– entity in the ethyl group is α-ester rearrangement to produce chlorodifluoroacetic acid and the corresponding radical. The yields of chlorofluoracetic acid (CF2ClC(O)OH) obtained were as follows: (34 ± 5)% and (86 ± 8)% for the reactions of Cl with CF2ClC(O)OCH3 and CF2ClC(O)OCH2CH3, respectively. The measured yields are rationalized in terms of mechanisms consisting of competitive reaction channels for the formed products in the oxidation, i.e. reaction with O2, α-ester rearrangement and a decomposition pathway. Atmospheric implications are discussed according to the rate coefficients obtained as a function of temperature and altitude, and regarding the formation of chlorofluorocarboxylic acid.
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Atmospheric Sink of methyl chlorodifluoroacetate and ethyl chlorodifluoroacetate: temperature dependent rate coefficients, product distribution of their reactions with Cl atoms and CF2ClC(O)OH formation
RSC Advances, 2016Co-Authors: María B. Blanco, Ian Barnes, Peter Wiesen, Mariano A. TeruelAbstract:Rate coefficients as a function of temperature and product distribution studies have been performed for the first time for the gas-phase reactions of chlorine atoms with methyl chlorodifluoracetate (k1) and ethyl chlorodifluoroacetate (k2) using the relative rate technique.
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Atmospheric Sink of (E)-3-Hexen-1-ol, (Z)-3-Hepten-1-ol, and (Z)-3-Octen-1-ol: Rate Coefficients and Mechanisms of the OH-Radical Initiated Degradation.
Environmental science & technology, 2015Co-Authors: Rodrigo G. Gibilisco, María B. Blanco, Ian Barnes, Peter Wiesen, Iustinian Bejan, Mariano A. TeruelAbstract:A kinetic study of the gas-phase reactions of OH radicals with three unsaturated biogenic alcohols, (E)-3-hexen-1-ol, (Z)-3-hepten-1-ol, and (Z)-3-octen-1-ol, has been performed. The rate coefficients obtained are (in units of 10(-10) cm(3) molecule(-1) s(-1)) k1 (OH + (E)-CH2(OH)CH2CH═CHCH2CH3) = (1.14 ± 0.14), k2 (OH + (Z)-CH2(OH)CH2CH═CHCH2CH2CH3) = (1.28 ± 0.23), and k3 (OH + (Z)-CH2(OH)CH2CH═CHCH2CH2CH2CH3) = (1.49 ± 0.35). In addition, a product study on the reactions of OH with (E)-3-hexen-1-ol and (Z)-3-hepten-1-ol is reported. All the experiments were performed at (298 ± 2) K and 1 atm of NOx-free air in a 1080 L photoreactor with in situ FTIR detection of organics. This work constitutes the first kinetic study of the reactions of OH radicals with (Z)-3-hepten-1-ol and (Z)-3-octen-1-ol as well as the first determination of the fate of the hydroxy alkoxy radicals formed in the title reactions. An analysis of the available rates of addition of OH and Cl to the double bond of different unsaturated alcohols at 298 K has shown that they can be related by the expression log kOH = (0.29 ± 0.04) log kCl - 10.8. The Atmospheric lifetimes of the alcohols studies were estimated to be around 1 h for reaction with OH radicals. The products formed in the title reactions are mainly carbonylic compounds that can contribute to the formation of ozone and PANs-type compounds in the troposphere.
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The Cl-initiated oxidation of CH_3C(O)OCH=CH_2, CH_3C(O)OCH_2CH=CH_2, and CH_2=CHC(O)O(CH_2)_3CH_3 in the troposphere
Environmental Science and Pollution Research, 2009Co-Authors: María B. Blanco, Ian Barnes, Peter Wiesen, Iustinian Bejan, Mariano A. TeruelAbstract:Background, aim, and scope Unsaturated esters are emitted to the atmosphere from biogenic and anthropogenic sources, including those from the polymer industry. Little information exists concerning the Atmospheric degradation of unsaturated esters, which are mainly initiated by OH radicals. Limited information is available on the degradation of alkenes by Cl atoms and almost no data exists for the reactions of unsaturated esters with Cl atoms. This data is necessary to assess the impact of such reactions in maritime environments where, under circumstances, OH radical- and Cl atom-initiated oxidation of the compounds can be important. Rate coefficients for the reactions of chlorine atoms with vinyl acetate, allyl acetate, and n -butyl acrylate have been determined at 298 ± 3 K and Atmospheric pressure. The kinetic data have been used in combination with that for structurally similar compounds to infer the kinetic contributions from the possible reaction channels to the overall reaction rate. Materials and methods The decay of the organics was followed using in situ Fourier transform infrared spectroscopy and the rate coefficients were determined using a relative kinetic method and different hydrocarbon reference compounds. Results The following room temperature rate coefficients (in cm^3 molecule^−1 s^−1) were obtained: k _1 (Cl + CH_3C(O)OCH=CH_2) = (2.68 ± 0.91) × 10^−10, k _2 (Cl + CH_3C(O)OCH_2CH=CH_2) = (1.30 ± 0.45) × 10^−10, and k _3 (Cl + CH_2=CHC(O)O(CH_2)_3CH_3) = (2.50 ± 0.78) × 10^−10, where the uncertainties are a combination of the 2 σ statistical errors from linear regression analyses and a contribution to cover uncertainties in the rate coefficients of the reference hydrocarbons. Discussion This is the first kinetic study of the title reactions under Atmospheric conditions. The kinetic data were analyzed in terms of reactivity trends and used to estimate the Atmospheric lifetimes of the esters and assess their potential importance in the marine atmosphere. Conclusions Although reaction with OH radicals is the major Atmospheric Sink for the unsaturated esters studied, reaction with Cl atoms can compete in the early morning hours in coastal areas where the Cl concentration can reach peak values as high as 1 × 10^5 atoms cm^−3. The calculated residence times show that the chemistry of unsaturated esters will impact air quality locally near their emission sources. Recommendations and perspectives The reactions need to be studied over the range of temperatures and pressures generally encountered in the marine atmosphere. In addition, product studies should also be performed as a function of temperature since this will allow degradation mechanisms to be derived, which are representative for the wide range of conditions occurring in marine environments. Inclusion of the kinetic and product data in tropospheric numerical models will allow an assessment of potential environmental impacts of the esters for different marine pollution scenarios.
María B. Blanco - One of the best experts on this subject based on the ideXlab platform.
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Atmospheric Sink of β-ocimene and camphene initiated by Cl atoms: kinetics and products at NOx free-air
RSC Advances, 2018Co-Authors: Elizabeth Gaona-colmán, María B. Blanco, Ian Barnes, Peter Wiesen, Mariano A. TeruelAbstract:Rate coefficients for the gas-phase reactions of Cl atoms with β-ocimene and camphene were determined to be (in units of 10−10 cm3 per molecule per s) 5.5 ± 0.7 and 3.3 ± 0.4, respectively. The experiments were performed by the relative technique in an environmental chamber with FTIR detection of the reactants at 298 K and 760 torr. Product identification experiments were carried out by gas chromatography with mass spectrometry detection (GC-MS) using the solid-phase microextraction (SPME) method employing on-fiber carbonyl compound derivatization with o-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine hydrochloride. An analysis of the available rates of addition of Cl atoms and OH radicals to the double bond of alkenes and cyclic and acyclic terpenes with a conjugated double bond at 298 K is presented. The Atmospheric persistence of these compounds was calculated taking into account the measured rate coefficients. In addition, tropospheric chemical mechanisms for the title reactions are postulated.
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Atmospheric Sink of methyl chlorodifluoroacetate and ethyl chlorodifluoroacetate temperature dependent rate coefficients product distribution of their reactions with cl atoms and cf2clc o oh formation
RSC Advances, 2016Co-Authors: María B. Blanco, Ian Barnes, Peter Wiesen, Mariano A. TeruelAbstract:Rate coefficients as a function of temperature have been measured for the first time for the gas-phase reactions of chlorine atoms with methyl chlorodifluoracetate (k1) and ethyl chlorodifluoroacetate (k2) using the relative rate technique. The experiments were carried out in a 1080 L photoreactor over the temperature range 287–313 K at a total pressure of 1000 ± 10 mbar of synthetic air using in situ FTIR spectroscopy to monitor reactants and products. The following Arrhenius expressions were obtained: k(MCDFA+Cl) = (9.6 ± 5.1) × 10−12 exp[−(1363 ± 79)/T] and k(ECDFA+Cl) = (64.4 ± 29.7) × 10−12 exp[−(1110 ± 68)/T]. The kinetic results are compared with previous experimental and theoretical studies. In addition, a product study of the reactions of Cl with methyl chlorodifluoracetate and ethyl chlorodifluoroacetate is reported. The results indicate that in the absence of NOx the main fate of the alkoxy radicals formed after H-atom abstraction by Cl from the –CH3 group in methyl chlorodifluoroacetate is reaction of the radical with O2 to form the mixed anhydride CF2ClC(O)OC(O)H. In the case of ethyl chlorodifluoroacetate the main fate of the alkoxy formed via H-atom abstraction by Cl from the –CH2– entity in the ethyl group is α-ester rearrangement to produce chlorodifluoroacetic acid and the corresponding radical. The yields of chlorofluoracetic acid (CF2ClC(O)OH) obtained were as follows: (34 ± 5)% and (86 ± 8)% for the reactions of Cl with CF2ClC(O)OCH3 and CF2ClC(O)OCH2CH3, respectively. The measured yields are rationalized in terms of mechanisms consisting of competitive reaction channels for the formed products in the oxidation, i.e. reaction with O2, α-ester rearrangement and a decomposition pathway. Atmospheric implications are discussed according to the rate coefficients obtained as a function of temperature and altitude, and regarding the formation of chlorofluorocarboxylic acid.
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Atmospheric Sink of methyl chlorodifluoroacetate and ethyl chlorodifluoroacetate: temperature dependent rate coefficients, product distribution of their reactions with Cl atoms and CF2ClC(O)OH formation
RSC Advances, 2016Co-Authors: María B. Blanco, Ian Barnes, Peter Wiesen, Mariano A. TeruelAbstract:Rate coefficients as a function of temperature and product distribution studies have been performed for the first time for the gas-phase reactions of chlorine atoms with methyl chlorodifluoracetate (k1) and ethyl chlorodifluoroacetate (k2) using the relative rate technique.
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Atmospheric Sink of (E)-3-Hexen-1-ol, (Z)-3-Hepten-1-ol, and (Z)-3-Octen-1-ol: Rate Coefficients and Mechanisms of the OH-Radical Initiated Degradation.
Environmental science & technology, 2015Co-Authors: Rodrigo G. Gibilisco, María B. Blanco, Ian Barnes, Peter Wiesen, Iustinian Bejan, Mariano A. TeruelAbstract:A kinetic study of the gas-phase reactions of OH radicals with three unsaturated biogenic alcohols, (E)-3-hexen-1-ol, (Z)-3-hepten-1-ol, and (Z)-3-octen-1-ol, has been performed. The rate coefficients obtained are (in units of 10(-10) cm(3) molecule(-1) s(-1)) k1 (OH + (E)-CH2(OH)CH2CH═CHCH2CH3) = (1.14 ± 0.14), k2 (OH + (Z)-CH2(OH)CH2CH═CHCH2CH2CH3) = (1.28 ± 0.23), and k3 (OH + (Z)-CH2(OH)CH2CH═CHCH2CH2CH2CH3) = (1.49 ± 0.35). In addition, a product study on the reactions of OH with (E)-3-hexen-1-ol and (Z)-3-hepten-1-ol is reported. All the experiments were performed at (298 ± 2) K and 1 atm of NOx-free air in a 1080 L photoreactor with in situ FTIR detection of organics. This work constitutes the first kinetic study of the reactions of OH radicals with (Z)-3-hepten-1-ol and (Z)-3-octen-1-ol as well as the first determination of the fate of the hydroxy alkoxy radicals formed in the title reactions. An analysis of the available rates of addition of OH and Cl to the double bond of different unsaturated alcohols at 298 K has shown that they can be related by the expression log kOH = (0.29 ± 0.04) log kCl - 10.8. The Atmospheric lifetimes of the alcohols studies were estimated to be around 1 h for reaction with OH radicals. The products formed in the title reactions are mainly carbonylic compounds that can contribute to the formation of ozone and PANs-type compounds in the troposphere.
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The Cl-initiated oxidation of CH_3C(O)OCH=CH_2, CH_3C(O)OCH_2CH=CH_2, and CH_2=CHC(O)O(CH_2)_3CH_3 in the troposphere
Environmental Science and Pollution Research, 2009Co-Authors: María B. Blanco, Ian Barnes, Peter Wiesen, Iustinian Bejan, Mariano A. TeruelAbstract:Background, aim, and scope Unsaturated esters are emitted to the atmosphere from biogenic and anthropogenic sources, including those from the polymer industry. Little information exists concerning the Atmospheric degradation of unsaturated esters, which are mainly initiated by OH radicals. Limited information is available on the degradation of alkenes by Cl atoms and almost no data exists for the reactions of unsaturated esters with Cl atoms. This data is necessary to assess the impact of such reactions in maritime environments where, under circumstances, OH radical- and Cl atom-initiated oxidation of the compounds can be important. Rate coefficients for the reactions of chlorine atoms with vinyl acetate, allyl acetate, and n -butyl acrylate have been determined at 298 ± 3 K and Atmospheric pressure. The kinetic data have been used in combination with that for structurally similar compounds to infer the kinetic contributions from the possible reaction channels to the overall reaction rate. Materials and methods The decay of the organics was followed using in situ Fourier transform infrared spectroscopy and the rate coefficients were determined using a relative kinetic method and different hydrocarbon reference compounds. Results The following room temperature rate coefficients (in cm^3 molecule^−1 s^−1) were obtained: k _1 (Cl + CH_3C(O)OCH=CH_2) = (2.68 ± 0.91) × 10^−10, k _2 (Cl + CH_3C(O)OCH_2CH=CH_2) = (1.30 ± 0.45) × 10^−10, and k _3 (Cl + CH_2=CHC(O)O(CH_2)_3CH_3) = (2.50 ± 0.78) × 10^−10, where the uncertainties are a combination of the 2 σ statistical errors from linear regression analyses and a contribution to cover uncertainties in the rate coefficients of the reference hydrocarbons. Discussion This is the first kinetic study of the title reactions under Atmospheric conditions. The kinetic data were analyzed in terms of reactivity trends and used to estimate the Atmospheric lifetimes of the esters and assess their potential importance in the marine atmosphere. Conclusions Although reaction with OH radicals is the major Atmospheric Sink for the unsaturated esters studied, reaction with Cl atoms can compete in the early morning hours in coastal areas where the Cl concentration can reach peak values as high as 1 × 10^5 atoms cm^−3. The calculated residence times show that the chemistry of unsaturated esters will impact air quality locally near their emission sources. Recommendations and perspectives The reactions need to be studied over the range of temperatures and pressures generally encountered in the marine atmosphere. In addition, product studies should also be performed as a function of temperature since this will allow degradation mechanisms to be derived, which are representative for the wide range of conditions occurring in marine environments. Inclusion of the kinetic and product data in tropospheric numerical models will allow an assessment of potential environmental impacts of the esters for different marine pollution scenarios.
Mark A. Young - One of the best experts on this subject based on the ideXlab platform.
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Heterogeneous interactions of calcite aerosol with sulfur dioxide and sulfur dioxide nitric acid mixtures
Physical chemistry chemical physics : PCCP, 2007Co-Authors: A. Preszler Prince, Paul D. Kleiber, Vicki H. Grassian, Mark A. YoungAbstract:The heterogeneous chemistry of sulfur dioxide with CaCO(3) (calcite) aerosol as a function of relative humidity (RH) has been studied under isolated particle conditions in an Atmospheric reaction chamber using infrared absorption spectroscopy. The reaction of SO(2) with calcite produced gas phase CO(2) as a product in addition to the conversion of the particulate carbonate to sulfite. The reaction extent was found to increase with elevated RH, as has been observed for the similar reaction with HNO(3), but much higher relative humidities were needed to significantly enhance the reaction. Mixed experiments in which calcite aerosol was exposed to both HNO(3) and SO(2) were also performed. The overall reaction extent at a given relative humidity did not appear to be increased by having both reactant gases present. The role of carbonate aerosol as an Atmospheric Sink for sulfur dioxide and particulate nitrogen and sulfur correlations are discussed.
Henri Wortham - One of the best experts on this subject based on the ideXlab platform.
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Photodegradation of Molecular Iodine on SiO2 Particles: Influence of Temperature and Relative Humidity
Journal of Nuclear Engineering and Radiation Science, 2020Co-Authors: Alexandre Figueiredo, Rafal Strekowski, L. Bosland, Amandine Durand, Henri WorthamAbstract:Abstract The heterogeneous photo-degradation of I2 was studied as a function of temperature and relative humidity in synthetic air to better understand its environmental fate. Two sets of experiments were carried out. In the first set of experiments, the temperature was T = (298±1)K and relative humidity was varied from ţ 2% to 75% RH under given experimental conditions. In the second set of experiments, the relative humidity within the Pyrex bulb was 40%RH and the temperature was varied from 283±1 ţ T(K) ţ 323±1. The obtained results show a considerably enhanced Atmospheric lifetime of molecular iodine adsorbed on solid media that does not depend on relative humidity of the environment. The obtained results show that the rate constant for the photolysis of molecular iodine adsorbed on model SiO2 particles depends on temperature and is reported to be J(T) = (1.24±1.4)×10(-2) × exp[(1482±345)/T]/s-1 over the measured temperature range. The heterogeneous Atmospheric residence time (T) of I2 adsorbed on solid media is calculated to range from 2 to 4.1 hours. The experimentally obtained heterogeneous lifetime of I2 is shown to be considerably longer than its destruction by its principal Atmospheric Sink, photolysis. The observed enhanced Atmospheric lifetime of I2 on heterogeneous media will likely have direct consequences on the Atmospheric transport of I2 that influences the toxicity or the oxidative capacity of the atmosphere.
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Photolytic degradation of molecular iodine adsorbed on model SiO2 particles.
The Science of the total environment, 2020Co-Authors: Alexandre Figueiredo, Rafal Strekowski, L. Bosland, Amandine Durand, Henri WorthamAbstract:Abstract A molecular derivatization method followed by gas chromatographic separation coupled with mass spectrometric detection was used to study photolytic degradation of I2 adsorbed on solid SiO2 particles. This heterogeneous photodegradation of I2 is studied at ambient temperature in synthetic air to better understand I2 Atmospheric dispersion and environmental fate. The obtained laboratory results show a considerably enhanced Atmospheric lifetime of molecular iodine adsorbed on solid media. The heterogeneous Atmospheric residence time (τ) of I2 is calculated to be τ ≈ 187 min, i.e., τ ≈ 3 h. The obtained heterogeneous lifetime of I2 is shown to be considerably longer than its destruction by its principal Atmospheric Sink, namely, photolysis. The observed enhanced Atmospheric lifetime of I2 on heterogeneous media will likely have direct consequences on the Atmospheric transport of I2 that influences the toxicity or the oxidative capacity of the atmosphere.