Evaluating the sensitivity of radical chemistry and ozone formation to ambient VOCs and NO.sub.x in Beijing
Measurements of OH, HO.sub.2, complex RO.sub.2 (alkene- and aromatic-related RO.sub.2) and total RO.sub.2 radicals taken during the integrated Study of AIR Pollution PROcesses in Beijing (AIRPRO) campaign in central Beijing in the summer of 2017, alongside observations of OH reactivity, are presente...
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| creator | Whalley, Lisa K Slater, Eloise J Woodward-Massey, Robert Ye, Chunxiang Lee, James D Squires, Freya Hopkins, James R Dunmore, Rachel E Shaw, Marvin Hamilton, Jacqueline F Lewis, Alastair C Mehra, Archit Worrall, Stephen D Bacak, Asan Bannan, Thomas J Coe, Hugh Percival, Carl J Ouyang, Bin Jones, Roderic L Crilley, Leigh R Kramer, Louisa J Bloss, William J Vu, Tuan Kotthaus, Simone Grimmond, Sue Sun, Yele Xu, Weiqi Yue, Siyao Ren, Lujie Acton, W. Joe F Hewitt, C. Nicholas Wang, Xinming Fu, Pingqing Heard, Dwayne E |
| description | Measurements of OH, HO.sub.2, complex RO.sub.2 (alkene- and aromatic-related RO.sub.2) and total RO.sub.2 radicals taken during the integrated Study of AIR Pollution PROcesses in Beijing (AIRPRO) campaign in central Beijing in the summer of 2017, alongside observations of OH reactivity, are presented. The concentrations of radicals were elevated, with OH reaching up to 2.8x107moleculecm-3, HO.sub.2 peaking at 1x109moleculecm-3 and the total RO.sub.2 concentration reaching 5.5x109moleculecm-3. OH reactivity (k(OH)) peaked at 89 s.sup.-1 during the night, with a minimum during the afternoon of â22s-1 on average. An experimental budget analysis, in which the rates of production and destruction of the radicals are compared, highlighted that although the sources and sinks of OH were balanced under high NO concentrations, the OH sinks exceeded the known sources (by 15 ppbv h.sup.-1) under the very low NO conditions ( |
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Joe F ; Hewitt, C. Nicholas ; Wang, Xinming ; Fu, Pingqing ; Heard, Dwayne E</creator><creatorcontrib>Whalley, Lisa K ; Slater, Eloise J ; Woodward-Massey, Robert ; Ye, Chunxiang ; Lee, James D ; Squires, Freya ; Hopkins, James R ; Dunmore, Rachel E ; Shaw, Marvin ; Hamilton, Jacqueline F ; Lewis, Alastair C ; Mehra, Archit ; Worrall, Stephen D ; Bacak, Asan ; Bannan, Thomas J ; Coe, Hugh ; Percival, Carl J ; Ouyang, Bin ; Jones, Roderic L ; Crilley, Leigh R ; Kramer, Louisa J ; Bloss, William J ; Vu, Tuan ; Kotthaus, Simone ; Grimmond, Sue ; Sun, Yele ; Xu, Weiqi ; Yue, Siyao ; Ren, Lujie ; Acton, W. Joe F ; Hewitt, C. Nicholas ; Wang, Xinming ; Fu, Pingqing ; Heard, Dwayne E</creatorcontrib><description>Measurements of OH, HO.sub.2, complex RO.sub.2 (alkene- and aromatic-related RO.sub.2) and total RO.sub.2 radicals taken during the integrated Study of AIR Pollution PROcesses in Beijing (AIRPRO) campaign in central Beijing in the summer of 2017, alongside observations of OH reactivity, are presented. The concentrations of radicals were elevated, with OH reaching up to 2.8x107moleculecm-3, HO.sub.2 peaking at 1x109moleculecm-3 and the total RO.sub.2 concentration reaching 5.5x109moleculecm-3. OH reactivity (k(OH)) peaked at 89 s.sup.-1 during the night, with a minimum during the afternoon of â22s-1 on average. An experimental budget analysis, in which the rates of production and destruction of the radicals are compared, highlighted that although the sources and sinks of OH were balanced under high NO concentrations, the OH sinks exceeded the known sources (by 15 ppbv h.sup.-1) under the very low NO conditions (<0.5 ppbv) experienced in the afternoons, demonstrating a missing OH source consistent with previous studies under high volatile organic compound (VOC) emissions and low NO loadings. Under the highest NO mixing ratios (104 ppbv), the HO.sub.2 production rate exceeded the rate of destruction by â50ppbvh-1, whilst the rate of destruction of total RO.sub.2 exceeded the production by the same rate, indicating that the net propagation rate of RO.sub.2 to HO.sub.2 may be substantially slower than assumed. If just 10 % of the RO.sub.2 radicals propagate to HO.sub.2 upon reaction with NO, the HO.sub.2 and RO.sub.2 budgets could be closed at high NO, but at low NO this lower RO.sub.2 to HO.sub.2 propagation rate revealed a missing RO.sub.2 sink that was similar in magnitude to the missing OH source. A detailed box model that incorporated the latest Master Chemical Mechanism (MCM3.3.1) reproduced the observed OH concentrations well but over-predicted the observed HO.sub.2 under low concentrations of NO (<1 ppbv) and under-predicted RO.sub.2 (both the complex RO.sub.2 fraction and other RO.sub.2 types which we classify as simple RO.sub.2) most significantly at the highest NO concentrations. The model also under-predicted the observed k(OH) consistently by â10s-1 across all NO.sub.x levels, highlighting that the good agreement for OH was fortuitous due to a cancellation of missing OH source and sink terms in its budget. Including heterogeneous loss of HO.sub.2 to aerosol surfaces did reduce the modelled HO.sub.2 concentrations in line with the observations but only at NO mixing ratios <0.3 ppbv. The inclusion of Cl atoms, formed from the photolysis of nitryl chloride, enhanced the modelled RO.sub.2 concentration on several mornings when the Cl atom concentration was calculated to exceed 1x104atomscm-3 and could reconcile the modelled and measured RO.sub.2 concentrations at these times. However, on other mornings, when the Cl atom concentration was lower, large under-predictions in total RO.sub.2 remained. Furthermore, the inclusion of Cl atom chemistry did not enhance the modelled RO.sub.2 beyond the first few hours after sunrise and so was unable to resolve the modelled under-prediction in RO.sub.2 observed at other times of the day. Model scenarios, in which missing VOC reactivity was included as an additional reaction that converted OH to RO.sub.2, highlighted that the modelled OH, HO.sub.2 and RO.sub.2 concentrations were sensitive to the choice of RO.sub.2 product. The level of modelled to measured agreement for HO.sub.2 and RO.sub.2 (both complex and simple) could be improved if the missing OH reactivity formed a larger RO.sub.2 species that was able to undergo reaction with NO, followed by isomerisation reactions reforming other RO.sub.2 species, before eventually generating HO.sub.2 . In this work an α-pinene-derived RO.sub.2 species was used as an example. In this simulation, consistent with the experimental budget analysis, the model underestimated the observed OH, indicating a missing OH source. The model uncertainty, with regards to the types of RO.sub.2 species present and the radicals they form upon reaction with NO (HO.sub.2 directly or another RO.sub.2 species), leads to over an order of magnitude less O.sub.3 production calculated from the predicted peroxy radicals than calculated from the observed peroxy radicals at the highest NO concentrations. This demonstrates the rate at which the larger RO.sub.2 species propagate to HO.sub.2, to another RO.sub.2 or indeed to OH needs to be understood to accurately simulate the rate of ozone production in environments such as Beijing, where large multifunctional VOCs are likely present.</description><identifier>ISSN: 1680-7316</identifier><identifier>EISSN: 1680-7324</identifier><language>eng</language><publisher>Copernicus GmbH</publisher><subject>Air pollution ; Olefins ; Volatile organic compounds</subject><ispartof>Atmospheric chemistry and physics, 2021-02, Vol.21 (3), p.2125</ispartof><rights>COPYRIGHT 2021 Copernicus GmbH</rights><lds50>peer_reviewed</lds50><woscitedreferencessubscribed>false</woscitedreferencessubscribed></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><link.rule.ids>314,780,784</link.rule.ids></links><search><creatorcontrib>Whalley, Lisa K</creatorcontrib><creatorcontrib>Slater, Eloise J</creatorcontrib><creatorcontrib>Woodward-Massey, Robert</creatorcontrib><creatorcontrib>Ye, Chunxiang</creatorcontrib><creatorcontrib>Lee, James D</creatorcontrib><creatorcontrib>Squires, Freya</creatorcontrib><creatorcontrib>Hopkins, James R</creatorcontrib><creatorcontrib>Dunmore, Rachel E</creatorcontrib><creatorcontrib>Shaw, Marvin</creatorcontrib><creatorcontrib>Hamilton, Jacqueline F</creatorcontrib><creatorcontrib>Lewis, Alastair C</creatorcontrib><creatorcontrib>Mehra, Archit</creatorcontrib><creatorcontrib>Worrall, Stephen D</creatorcontrib><creatorcontrib>Bacak, Asan</creatorcontrib><creatorcontrib>Bannan, Thomas J</creatorcontrib><creatorcontrib>Coe, Hugh</creatorcontrib><creatorcontrib>Percival, Carl J</creatorcontrib><creatorcontrib>Ouyang, Bin</creatorcontrib><creatorcontrib>Jones, Roderic L</creatorcontrib><creatorcontrib>Crilley, Leigh R</creatorcontrib><creatorcontrib>Kramer, Louisa J</creatorcontrib><creatorcontrib>Bloss, William J</creatorcontrib><creatorcontrib>Vu, Tuan</creatorcontrib><creatorcontrib>Kotthaus, Simone</creatorcontrib><creatorcontrib>Grimmond, Sue</creatorcontrib><creatorcontrib>Sun, Yele</creatorcontrib><creatorcontrib>Xu, Weiqi</creatorcontrib><creatorcontrib>Yue, Siyao</creatorcontrib><creatorcontrib>Ren, Lujie</creatorcontrib><creatorcontrib>Acton, W. Joe F</creatorcontrib><creatorcontrib>Hewitt, C. Nicholas</creatorcontrib><creatorcontrib>Wang, Xinming</creatorcontrib><creatorcontrib>Fu, Pingqing</creatorcontrib><creatorcontrib>Heard, Dwayne E</creatorcontrib><title>Evaluating the sensitivity of radical chemistry and ozone formation to ambient VOCs and NO.sub.x in Beijing</title><title>Atmospheric chemistry and physics</title><description>Measurements of OH, HO.sub.2, complex RO.sub.2 (alkene- and aromatic-related RO.sub.2) and total RO.sub.2 radicals taken during the integrated Study of AIR Pollution PROcesses in Beijing (AIRPRO) campaign in central Beijing in the summer of 2017, alongside observations of OH reactivity, are presented. The concentrations of radicals were elevated, with OH reaching up to 2.8x107moleculecm-3, HO.sub.2 peaking at 1x109moleculecm-3 and the total RO.sub.2 concentration reaching 5.5x109moleculecm-3. OH reactivity (k(OH)) peaked at 89 s.sup.-1 during the night, with a minimum during the afternoon of â22s-1 on average. An experimental budget analysis, in which the rates of production and destruction of the radicals are compared, highlighted that although the sources and sinks of OH were balanced under high NO concentrations, the OH sinks exceeded the known sources (by 15 ppbv h.sup.-1) under the very low NO conditions (<0.5 ppbv) experienced in the afternoons, demonstrating a missing OH source consistent with previous studies under high volatile organic compound (VOC) emissions and low NO loadings. Under the highest NO mixing ratios (104 ppbv), the HO.sub.2 production rate exceeded the rate of destruction by â50ppbvh-1, whilst the rate of destruction of total RO.sub.2 exceeded the production by the same rate, indicating that the net propagation rate of RO.sub.2 to HO.sub.2 may be substantially slower than assumed. If just 10 % of the RO.sub.2 radicals propagate to HO.sub.2 upon reaction with NO, the HO.sub.2 and RO.sub.2 budgets could be closed at high NO, but at low NO this lower RO.sub.2 to HO.sub.2 propagation rate revealed a missing RO.sub.2 sink that was similar in magnitude to the missing OH source. A detailed box model that incorporated the latest Master Chemical Mechanism (MCM3.3.1) reproduced the observed OH concentrations well but over-predicted the observed HO.sub.2 under low concentrations of NO (<1 ppbv) and under-predicted RO.sub.2 (both the complex RO.sub.2 fraction and other RO.sub.2 types which we classify as simple RO.sub.2) most significantly at the highest NO concentrations. The model also under-predicted the observed k(OH) consistently by â10s-1 across all NO.sub.x levels, highlighting that the good agreement for OH was fortuitous due to a cancellation of missing OH source and sink terms in its budget. Including heterogeneous loss of HO.sub.2 to aerosol surfaces did reduce the modelled HO.sub.2 concentrations in line with the observations but only at NO mixing ratios <0.3 ppbv. The inclusion of Cl atoms, formed from the photolysis of nitryl chloride, enhanced the modelled RO.sub.2 concentration on several mornings when the Cl atom concentration was calculated to exceed 1x104atomscm-3 and could reconcile the modelled and measured RO.sub.2 concentrations at these times. However, on other mornings, when the Cl atom concentration was lower, large under-predictions in total RO.sub.2 remained. Furthermore, the inclusion of Cl atom chemistry did not enhance the modelled RO.sub.2 beyond the first few hours after sunrise and so was unable to resolve the modelled under-prediction in RO.sub.2 observed at other times of the day. Model scenarios, in which missing VOC reactivity was included as an additional reaction that converted OH to RO.sub.2, highlighted that the modelled OH, HO.sub.2 and RO.sub.2 concentrations were sensitive to the choice of RO.sub.2 product. The level of modelled to measured agreement for HO.sub.2 and RO.sub.2 (both complex and simple) could be improved if the missing OH reactivity formed a larger RO.sub.2 species that was able to undergo reaction with NO, followed by isomerisation reactions reforming other RO.sub.2 species, before eventually generating HO.sub.2 . In this work an α-pinene-derived RO.sub.2 species was used as an example. In this simulation, consistent with the experimental budget analysis, the model underestimated the observed OH, indicating a missing OH source. The model uncertainty, with regards to the types of RO.sub.2 species present and the radicals they form upon reaction with NO (HO.sub.2 directly or another RO.sub.2 species), leads to over an order of magnitude less O.sub.3 production calculated from the predicted peroxy radicals than calculated from the observed peroxy radicals at the highest NO concentrations. This demonstrates the rate at which the larger RO.sub.2 species propagate to HO.sub.2, to another RO.sub.2 or indeed to OH needs to be understood to accurately simulate the rate of ozone production in environments such as Beijing, where large multifunctional VOCs are likely present.</description><subject>Air pollution</subject><subject>Olefins</subject><subject>Volatile organic compounds</subject><issn>1680-7316</issn><issn>1680-7324</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2021</creationdate><recordtype>article</recordtype><recordid>eNptj1tLwzAUx4soOKff4YBPPrQkTRrbxzmmDoYFb68lzaXL7BJosrH56Y0XxIEcDufP4fc_l6NkhFmJ0muS0-Nfjdlpcub9CqG8QJiOkrfZlvcbHoztICwVeGW9CWZrwh6choFLI3gPYqnWxodhD9xKcO_OKtBuWEejsxAc8HVrlA3wWk_9F_NQZ37TZjswFm6UWcUF58mJ5r1XFz91nLzczp6n9-mivptPJ4u0wwizlBBEJUKtkKUsiKpYyTRupcJElznVtNRItJVi7FPItsK8khLTmILltNBknFx-z-14rxpjtQsDF_F-0UxYgRnBJWORyv6hYsj4qogPahP7B4arA0NkgtqFjm-8b-ZPj3_ZD6ZkcyE</recordid><startdate>20210212</startdate><enddate>20210212</enddate><creator>Whalley, Lisa K</creator><creator>Slater, Eloise J</creator><creator>Woodward-Massey, Robert</creator><creator>Ye, Chunxiang</creator><creator>Lee, James D</creator><creator>Squires, Freya</creator><creator>Hopkins, James R</creator><creator>Dunmore, Rachel E</creator><creator>Shaw, Marvin</creator><creator>Hamilton, Jacqueline F</creator><creator>Lewis, Alastair C</creator><creator>Mehra, Archit</creator><creator>Worrall, Stephen D</creator><creator>Bacak, Asan</creator><creator>Bannan, Thomas J</creator><creator>Coe, Hugh</creator><creator>Percival, Carl J</creator><creator>Ouyang, Bin</creator><creator>Jones, Roderic L</creator><creator>Crilley, Leigh R</creator><creator>Kramer, Louisa J</creator><creator>Bloss, William J</creator><creator>Vu, Tuan</creator><creator>Kotthaus, Simone</creator><creator>Grimmond, Sue</creator><creator>Sun, Yele</creator><creator>Xu, Weiqi</creator><creator>Yue, Siyao</creator><creator>Ren, Lujie</creator><creator>Acton, W. Joe F</creator><creator>Hewitt, C. Nicholas</creator><creator>Wang, Xinming</creator><creator>Fu, Pingqing</creator><creator>Heard, Dwayne E</creator><general>Copernicus GmbH</general><scope>ISR</scope></search><sort><creationdate>20210212</creationdate><title>Evaluating the sensitivity of radical chemistry and ozone formation to ambient VOCs and NO.sub.x in Beijing</title><author>Whalley, Lisa K ; Slater, Eloise J ; Woodward-Massey, Robert ; Ye, Chunxiang ; Lee, James D ; Squires, Freya ; Hopkins, James R ; Dunmore, Rachel E ; Shaw, Marvin ; Hamilton, Jacqueline F ; Lewis, Alastair C ; Mehra, Archit ; Worrall, Stephen D ; Bacak, Asan ; Bannan, Thomas J ; Coe, Hugh ; Percival, Carl J ; Ouyang, Bin ; Jones, Roderic L ; Crilley, Leigh R ; Kramer, Louisa J ; Bloss, William J ; Vu, Tuan ; Kotthaus, Simone ; Grimmond, Sue ; Sun, Yele ; Xu, Weiqi ; Yue, Siyao ; Ren, Lujie ; Acton, W. Joe F ; Hewitt, C. Nicholas ; Wang, Xinming ; Fu, Pingqing ; Heard, Dwayne E</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-g1016-3304d00bcd8d53e9686f1bde13f824f48f0cb9e668f0cdb91a9dd14dd1c6245f3</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>2021</creationdate><topic>Air pollution</topic><topic>Olefins</topic><topic>Volatile organic compounds</topic><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Whalley, Lisa K</creatorcontrib><creatorcontrib>Slater, Eloise J</creatorcontrib><creatorcontrib>Woodward-Massey, Robert</creatorcontrib><creatorcontrib>Ye, Chunxiang</creatorcontrib><creatorcontrib>Lee, James D</creatorcontrib><creatorcontrib>Squires, Freya</creatorcontrib><creatorcontrib>Hopkins, James R</creatorcontrib><creatorcontrib>Dunmore, Rachel E</creatorcontrib><creatorcontrib>Shaw, Marvin</creatorcontrib><creatorcontrib>Hamilton, Jacqueline F</creatorcontrib><creatorcontrib>Lewis, Alastair C</creatorcontrib><creatorcontrib>Mehra, Archit</creatorcontrib><creatorcontrib>Worrall, Stephen D</creatorcontrib><creatorcontrib>Bacak, Asan</creatorcontrib><creatorcontrib>Bannan, Thomas J</creatorcontrib><creatorcontrib>Coe, Hugh</creatorcontrib><creatorcontrib>Percival, Carl J</creatorcontrib><creatorcontrib>Ouyang, Bin</creatorcontrib><creatorcontrib>Jones, Roderic L</creatorcontrib><creatorcontrib>Crilley, Leigh R</creatorcontrib><creatorcontrib>Kramer, Louisa J</creatorcontrib><creatorcontrib>Bloss, William J</creatorcontrib><creatorcontrib>Vu, Tuan</creatorcontrib><creatorcontrib>Kotthaus, Simone</creatorcontrib><creatorcontrib>Grimmond, Sue</creatorcontrib><creatorcontrib>Sun, Yele</creatorcontrib><creatorcontrib>Xu, Weiqi</creatorcontrib><creatorcontrib>Yue, Siyao</creatorcontrib><creatorcontrib>Ren, Lujie</creatorcontrib><creatorcontrib>Acton, W. Joe F</creatorcontrib><creatorcontrib>Hewitt, C. Nicholas</creatorcontrib><creatorcontrib>Wang, Xinming</creatorcontrib><creatorcontrib>Fu, Pingqing</creatorcontrib><creatorcontrib>Heard, Dwayne E</creatorcontrib><collection>Gale In Context: Science</collection><jtitle>Atmospheric chemistry and physics</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Whalley, Lisa K</au><au>Slater, Eloise J</au><au>Woodward-Massey, Robert</au><au>Ye, Chunxiang</au><au>Lee, James D</au><au>Squires, Freya</au><au>Hopkins, James R</au><au>Dunmore, Rachel E</au><au>Shaw, Marvin</au><au>Hamilton, Jacqueline F</au><au>Lewis, Alastair C</au><au>Mehra, Archit</au><au>Worrall, Stephen D</au><au>Bacak, Asan</au><au>Bannan, Thomas J</au><au>Coe, Hugh</au><au>Percival, Carl J</au><au>Ouyang, Bin</au><au>Jones, Roderic L</au><au>Crilley, Leigh R</au><au>Kramer, Louisa J</au><au>Bloss, William J</au><au>Vu, Tuan</au><au>Kotthaus, Simone</au><au>Grimmond, Sue</au><au>Sun, Yele</au><au>Xu, Weiqi</au><au>Yue, Siyao</au><au>Ren, Lujie</au><au>Acton, W. Joe F</au><au>Hewitt, C. Nicholas</au><au>Wang, Xinming</au><au>Fu, Pingqing</au><au>Heard, Dwayne E</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Evaluating the sensitivity of radical chemistry and ozone formation to ambient VOCs and NO.sub.x in Beijing</atitle><jtitle>Atmospheric chemistry and physics</jtitle><date>2021-02-12</date><risdate>2021</risdate><volume>21</volume><issue>3</issue><spage>2125</spage><pages>2125-</pages><issn>1680-7316</issn><eissn>1680-7324</eissn><abstract>Measurements of OH, HO.sub.2, complex RO.sub.2 (alkene- and aromatic-related RO.sub.2) and total RO.sub.2 radicals taken during the integrated Study of AIR Pollution PROcesses in Beijing (AIRPRO) campaign in central Beijing in the summer of 2017, alongside observations of OH reactivity, are presented. The concentrations of radicals were elevated, with OH reaching up to 2.8x107moleculecm-3, HO.sub.2 peaking at 1x109moleculecm-3 and the total RO.sub.2 concentration reaching 5.5x109moleculecm-3. OH reactivity (k(OH)) peaked at 89 s.sup.-1 during the night, with a minimum during the afternoon of â22s-1 on average. An experimental budget analysis, in which the rates of production and destruction of the radicals are compared, highlighted that although the sources and sinks of OH were balanced under high NO concentrations, the OH sinks exceeded the known sources (by 15 ppbv h.sup.-1) under the very low NO conditions (<0.5 ppbv) experienced in the afternoons, demonstrating a missing OH source consistent with previous studies under high volatile organic compound (VOC) emissions and low NO loadings. Under the highest NO mixing ratios (104 ppbv), the HO.sub.2 production rate exceeded the rate of destruction by â50ppbvh-1, whilst the rate of destruction of total RO.sub.2 exceeded the production by the same rate, indicating that the net propagation rate of RO.sub.2 to HO.sub.2 may be substantially slower than assumed. If just 10 % of the RO.sub.2 radicals propagate to HO.sub.2 upon reaction with NO, the HO.sub.2 and RO.sub.2 budgets could be closed at high NO, but at low NO this lower RO.sub.2 to HO.sub.2 propagation rate revealed a missing RO.sub.2 sink that was similar in magnitude to the missing OH source. A detailed box model that incorporated the latest Master Chemical Mechanism (MCM3.3.1) reproduced the observed OH concentrations well but over-predicted the observed HO.sub.2 under low concentrations of NO (<1 ppbv) and under-predicted RO.sub.2 (both the complex RO.sub.2 fraction and other RO.sub.2 types which we classify as simple RO.sub.2) most significantly at the highest NO concentrations. The model also under-predicted the observed k(OH) consistently by â10s-1 across all NO.sub.x levels, highlighting that the good agreement for OH was fortuitous due to a cancellation of missing OH source and sink terms in its budget. Including heterogeneous loss of HO.sub.2 to aerosol surfaces did reduce the modelled HO.sub.2 concentrations in line with the observations but only at NO mixing ratios <0.3 ppbv. The inclusion of Cl atoms, formed from the photolysis of nitryl chloride, enhanced the modelled RO.sub.2 concentration on several mornings when the Cl atom concentration was calculated to exceed 1x104atomscm-3 and could reconcile the modelled and measured RO.sub.2 concentrations at these times. However, on other mornings, when the Cl atom concentration was lower, large under-predictions in total RO.sub.2 remained. Furthermore, the inclusion of Cl atom chemistry did not enhance the modelled RO.sub.2 beyond the first few hours after sunrise and so was unable to resolve the modelled under-prediction in RO.sub.2 observed at other times of the day. Model scenarios, in which missing VOC reactivity was included as an additional reaction that converted OH to RO.sub.2, highlighted that the modelled OH, HO.sub.2 and RO.sub.2 concentrations were sensitive to the choice of RO.sub.2 product. The level of modelled to measured agreement for HO.sub.2 and RO.sub.2 (both complex and simple) could be improved if the missing OH reactivity formed a larger RO.sub.2 species that was able to undergo reaction with NO, followed by isomerisation reactions reforming other RO.sub.2 species, before eventually generating HO.sub.2 . In this work an α-pinene-derived RO.sub.2 species was used as an example. In this simulation, consistent with the experimental budget analysis, the model underestimated the observed OH, indicating a missing OH source. The model uncertainty, with regards to the types of RO.sub.2 species present and the radicals they form upon reaction with NO (HO.sub.2 directly or another RO.sub.2 species), leads to over an order of magnitude less O.sub.3 production calculated from the predicted peroxy radicals than calculated from the observed peroxy radicals at the highest NO concentrations. This demonstrates the rate at which the larger RO.sub.2 species propagate to HO.sub.2, to another RO.sub.2 or indeed to OH needs to be understood to accurately simulate the rate of ozone production in environments such as Beijing, where large multifunctional VOCs are likely present.</abstract><pub>Copernicus GmbH</pub><tpages>2125</tpages></addata></record> |
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| identifier | ISSN: 1680-7316 |
| ispartof | Atmospheric chemistry and physics, 2021-02, Vol.21 (3), p.2125 |
| issn | 1680-7316 1680-7324 |
| language | eng |
| recordid | cdi_gale_infotracmisc_A651631866 |
| source | DOAJ Directory of Open Access Journals; EZB-FREE-00999 freely available EZB journals; Free Full-Text Journals in Chemistry |
| subjects | Air pollution Olefins Volatile organic compounds |
| title | Evaluating the sensitivity of radical chemistry and ozone formation to ambient VOCs and NO.sub.x in Beijing |
| url | https://sfx.bib-bvb.de/sfx_tum?ctx_ver=Z39.88-2004&ctx_enc=info:ofi/enc:UTF-8&ctx_tim=2024-12-24T04%3A05%3A08IST&url_ver=Z39.88-2004&url_ctx_fmt=infofi/fmt:kev:mtx:ctx&rfr_id=info:sid/primo.exlibrisgroup.com:primo3-Article-gale&rft_val_fmt=info:ofi/fmt:kev:mtx:journal&rft.genre=article&rft.atitle=Evaluating%20the%20sensitivity%20of%20radical%20chemistry%20and%20ozone%20formation%20to%20ambient%20VOCs%20and%20NO.sub.x%20in%20Beijing&rft.jtitle=Atmospheric%20chemistry%20and%20physics&rft.au=Whalley,%20Lisa%20K&rft.date=2021-02-12&rft.volume=21&rft.issue=3&rft.spage=2125&rft.pages=2125-&rft.issn=1680-7316&rft.eissn=1680-7324&rft_id=info:doi/&rft_dat=%3Cgale%3EA651631866%3C/gale%3E%3Curl%3E%3C/url%3E&disable_directlink=true&sfx.directlink=off&sfx.report_link=0&rft_id=info:oai/&rft_id=info:pmid/&rft_galeid=A651631866&rfr_iscdi=true |