Isotopic constraints on heterogeneous sulfate production in Beijing haze
Discerning mechanisms of sulfate formation during fine-particle pollution (referred to as haze hereafter) in Beijing is important for understanding the rapid evolution of haze and for developing cost-effective air pollution mitigation strategies. Here we present observations of the oxygen-17 exce...
| Main Authors: | , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2018-04-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/18/5515/2018/acp-18-5515-2018.pdf |
| _version_ | 1818560123351597056 |
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| author | P. He B. Alexander L. Geng X. Chi S. Fan H. Zhan H. Kang G. Zheng G. Zheng Y. Cheng Y. Cheng H. Su H. Su C. Liu C. Liu C. Liu Z. Xie Z. Xie Z. Xie |
| author_facet | P. He B. Alexander L. Geng X. Chi S. Fan H. Zhan H. Kang G. Zheng G. Zheng Y. Cheng Y. Cheng H. Su H. Su C. Liu C. Liu C. Liu Z. Xie Z. Xie Z. Xie |
| author_sort | P. He |
| collection | DOAJ |
| description | Discerning mechanisms of sulfate formation during fine-particle pollution
(referred to as haze hereafter) in Beijing is important for understanding the
rapid evolution of haze and for developing cost-effective air pollution
mitigation strategies. Here we present observations of the oxygen-17 excess
of PM<sub>2.5</sub> sulfate (Δ<sup>17</sup>O(SO<sub>4</sub><sup>2−</sup>)) collected in Beijing
haze from October 2014 to January 2015 to constrain possible sulfate
formation pathways. Throughout the sampling campaign, the 12-hourly
averaged PM<sub>2.5</sub> concentrations ranged from 16 to
323 µg m<sup>−3</sup> with a mean of (141 ± 88
(1<i>σ</i>)) µg m<sup>−3</sup>, with SO<sub>4</sub><sup>2−</sup> representing
8–25 % of PM<sub>2.5</sub> mass. The observed Δ<sup>17</sup>O(SO<sub>4</sub><sup>2−</sup>)
varied from 0.1 to 1.6 ‰ with a mean of
(0.9 ± 0.3) ‰. Δ<sup>17</sup>O(SO<sub>4</sub><sup>2−</sup>) increased with
PM<sub>2.5</sub> levels in October 2014 while the opposite trend was observed from
November 2014 to January 2015. Our estimate suggested that in-cloud reactions
dominated sulfate production on polluted days (PDs,
PM<sub>2.5</sub> ≥ 75 µg m<sup>−3</sup>) of Case II in October 2014 due to
the relatively high cloud liquid water content, with a fractional
contribution of up to 68 %. During PDs of Cases I and III–V,
heterogeneous sulfate production (<i>P</i><sub>het</sub>) was estimated to
contribute 41–54 % to total sulfate formation with a mean of
(48 ± 5) %. For the specific mechanisms of heterogeneous oxidation
of SO<sub>2</sub>, chemical reaction kinetics calculations suggested S(IV)
( = SO<sub>2</sub> ⚫ H<sub>2</sub>O + HSO<sub>3</sub><sup>−</sup> + SO<sub>3</sub><sup>2−</sup>)
oxidation by H<sub>2</sub>O<sub>2</sub> in aerosol water accounted for 5–13 % of
<i>P</i><sub>het</sub>. The relative importance of heterogeneous sulfate production
by other mechanisms was constrained by our observed
Δ<sup>17</sup>O(SO<sub>4</sub><sup>2−</sup>). Heterogeneous sulfate production via S(IV)
oxidation by O<sub>3</sub> was estimated to contribute 21–22 % of
<i>P</i><sub>het</sub> on average. Heterogeneous sulfate production pathways that
result in zero-Δ<sup>17</sup>O(SO<sub>4</sub><sup>2−</sup>), such as S(IV) oxidation by
NO<sub>2</sub> in aerosol water and/or by O<sub>2</sub> via a radical chain mechanism,
contributed the remaining 66–73 % of <i>P</i><sub>het</sub>. The assumption
about the thermodynamic state of aerosols (stable or metastable) was found to
significantly influence the calculated aerosol pH (7.6 ± 0.1 or
4.7 ± 1.1, respectively), and thus influence the relative importance of
heterogeneous sulfate production via S(IV) oxidation by NO<sub>2</sub> and by
O<sub>2</sub>. Our local atmospheric conditions-based calculations suggest sulfate
formation via NO<sub>2</sub> oxidation can be the dominant pathway in aerosols at
high-pH conditions calculated assuming stable state while S(IV) oxidation by
O<sub>2</sub> can be the dominant pathway providing that highly acidic aerosols
(pH ≤ 3) exist. Our local atmospheric-conditions-based calculations
illustrate the utility of Δ<sup>17</sup>O(SO<sub>4</sub><sup>2−</sup>) for quantifying
sulfate formation pathways, but this estimate may be further improved with
future regional modeling work. |
| first_indexed | 2024-12-14T00:34:22Z |
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| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-14T00:34:22Z |
| publishDate | 2018-04-01 |
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| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-637ede2859ca424f8eb8c1dc8874bc7d2022-12-21T23:24:44ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242018-04-01185515552810.5194/acp-18-5515-2018Isotopic constraints on heterogeneous sulfate production in Beijing hazeP. He0B. Alexander1L. Geng2X. Chi3S. Fan4H. Zhan5H. Kang6G. Zheng7G. Zheng8Y. Cheng9Y. Cheng10H. Su11H. Su12C. Liu13C. Liu14C. Liu15Z. Xie16Z. Xie17Z. Xie18Anhui Province Key Laboratory of Polar Environment and Global Change, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, ChinaDepartment of Atmospheric Sciences, University of Washington, Seattle, WA 98195, USAAnhui Province Key Laboratory of Polar Environment and Global Change, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, ChinaAnhui Province Key Laboratory of Polar Environment and Global Change, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, ChinaAnhui Province Key Laboratory of Polar Environment and Global Change, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, ChinaAnhui Province Key Laboratory of Polar Environment and Global Change, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, ChinaAnhui Province Key Laboratory of Polar Environment and Global Change, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, ChinaMultiphase Chemistry Department, Max Planck Institute for Chemistry, Mainz 55128, Germanynow at: Atmospheric Sciences Division, Brookhaven National Laboratory, Upton, NY 11973, USAMultiphase Chemistry Department, Max Planck Institute for Chemistry, Mainz 55128, GermanyJinan University, Institute for Environment and Climate Research, Guangzhou, Guangdong 511443, ChinaMultiphase Chemistry Department, Max Planck Institute for Chemistry, Mainz 55128, GermanyJinan University, Institute for Environment and Climate Research, Guangzhou, Guangdong 511443, ChinaAnhui Province Key Laboratory of Polar Environment and Global Change, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, ChinaKey Lab of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei, Anhui 230031, ChinaCenter for Excellence in Urban Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, Fujian 361021, ChinaAnhui Province Key Laboratory of Polar Environment and Global Change, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, ChinaKey Lab of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei, Anhui 230031, ChinaCenter for Excellence in Urban Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, Fujian 361021, ChinaDiscerning mechanisms of sulfate formation during fine-particle pollution (referred to as haze hereafter) in Beijing is important for understanding the rapid evolution of haze and for developing cost-effective air pollution mitigation strategies. Here we present observations of the oxygen-17 excess of PM<sub>2.5</sub> sulfate (Δ<sup>17</sup>O(SO<sub>4</sub><sup>2−</sup>)) collected in Beijing haze from October 2014 to January 2015 to constrain possible sulfate formation pathways. Throughout the sampling campaign, the 12-hourly averaged PM<sub>2.5</sub> concentrations ranged from 16 to 323 µg m<sup>−3</sup> with a mean of (141 ± 88 (1<i>σ</i>)) µg m<sup>−3</sup>, with SO<sub>4</sub><sup>2−</sup> representing 8–25 % of PM<sub>2.5</sub> mass. The observed Δ<sup>17</sup>O(SO<sub>4</sub><sup>2−</sup>) varied from 0.1 to 1.6 ‰ with a mean of (0.9 ± 0.3) ‰. Δ<sup>17</sup>O(SO<sub>4</sub><sup>2−</sup>) increased with PM<sub>2.5</sub> levels in October 2014 while the opposite trend was observed from November 2014 to January 2015. Our estimate suggested that in-cloud reactions dominated sulfate production on polluted days (PDs, PM<sub>2.5</sub> ≥ 75 µg m<sup>−3</sup>) of Case II in October 2014 due to the relatively high cloud liquid water content, with a fractional contribution of up to 68 %. During PDs of Cases I and III–V, heterogeneous sulfate production (<i>P</i><sub>het</sub>) was estimated to contribute 41–54 % to total sulfate formation with a mean of (48 ± 5) %. For the specific mechanisms of heterogeneous oxidation of SO<sub>2</sub>, chemical reaction kinetics calculations suggested S(IV) ( = SO<sub>2</sub> ⚫ H<sub>2</sub>O + HSO<sub>3</sub><sup>−</sup> + SO<sub>3</sub><sup>2−</sup>) oxidation by H<sub>2</sub>O<sub>2</sub> in aerosol water accounted for 5–13 % of <i>P</i><sub>het</sub>. The relative importance of heterogeneous sulfate production by other mechanisms was constrained by our observed Δ<sup>17</sup>O(SO<sub>4</sub><sup>2−</sup>). Heterogeneous sulfate production via S(IV) oxidation by O<sub>3</sub> was estimated to contribute 21–22 % of <i>P</i><sub>het</sub> on average. Heterogeneous sulfate production pathways that result in zero-Δ<sup>17</sup>O(SO<sub>4</sub><sup>2−</sup>), such as S(IV) oxidation by NO<sub>2</sub> in aerosol water and/or by O<sub>2</sub> via a radical chain mechanism, contributed the remaining 66–73 % of <i>P</i><sub>het</sub>. The assumption about the thermodynamic state of aerosols (stable or metastable) was found to significantly influence the calculated aerosol pH (7.6 ± 0.1 or 4.7 ± 1.1, respectively), and thus influence the relative importance of heterogeneous sulfate production via S(IV) oxidation by NO<sub>2</sub> and by O<sub>2</sub>. Our local atmospheric conditions-based calculations suggest sulfate formation via NO<sub>2</sub> oxidation can be the dominant pathway in aerosols at high-pH conditions calculated assuming stable state while S(IV) oxidation by O<sub>2</sub> can be the dominant pathway providing that highly acidic aerosols (pH ≤ 3) exist. Our local atmospheric-conditions-based calculations illustrate the utility of Δ<sup>17</sup>O(SO<sub>4</sub><sup>2−</sup>) for quantifying sulfate formation pathways, but this estimate may be further improved with future regional modeling work.https://www.atmos-chem-phys.net/18/5515/2018/acp-18-5515-2018.pdf |
| spellingShingle | P. He B. Alexander L. Geng X. Chi S. Fan H. Zhan H. Kang G. Zheng G. Zheng Y. Cheng Y. Cheng H. Su H. Su C. Liu C. Liu C. Liu Z. Xie Z. Xie Z. Xie Isotopic constraints on heterogeneous sulfate production in Beijing haze Atmospheric Chemistry and Physics |
| title | Isotopic constraints on heterogeneous sulfate production in Beijing haze |
| title_full | Isotopic constraints on heterogeneous sulfate production in Beijing haze |
| title_fullStr | Isotopic constraints on heterogeneous sulfate production in Beijing haze |
| title_full_unstemmed | Isotopic constraints on heterogeneous sulfate production in Beijing haze |
| title_short | Isotopic constraints on heterogeneous sulfate production in Beijing haze |
| title_sort | isotopic constraints on heterogeneous sulfate production in beijing haze |
| url | https://www.atmos-chem-phys.net/18/5515/2018/acp-18-5515-2018.pdf |
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