Dynamic changes in optical and chemical properties of tar ball aerosols by atmospheric photochemical aging
<p>Following wood pyrolysis, tar ball aerosols were laboratory generated from wood tar separated into polar and nonpolar phases. Chemical information of fresh tar balls was obtained from a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and single-particle laser desorptio...
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Copernicus Publications
2019-01-01
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Series: | Atmospheric Chemistry and Physics |
Online Access: | https://www.atmos-chem-phys.net/19/139/2019/acp-19-139-2019.pdf |
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record_format |
Article |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
C. Li Q. He J. Schade J. Passig J. Passig R. Zimmermann R. Zimmermann D. Meidan A. Laskin Y. Rudich |
spellingShingle |
C. Li Q. He J. Schade J. Passig J. Passig R. Zimmermann R. Zimmermann D. Meidan A. Laskin Y. Rudich Dynamic changes in optical and chemical properties of tar ball aerosols by atmospheric photochemical aging Atmospheric Chemistry and Physics |
author_facet |
C. Li Q. He J. Schade J. Passig J. Passig R. Zimmermann R. Zimmermann D. Meidan A. Laskin Y. Rudich |
author_sort |
C. Li |
title |
Dynamic changes in optical and chemical properties of tar ball aerosols by atmospheric photochemical aging |
title_short |
Dynamic changes in optical and chemical properties of tar ball aerosols by atmospheric photochemical aging |
title_full |
Dynamic changes in optical and chemical properties of tar ball aerosols by atmospheric photochemical aging |
title_fullStr |
Dynamic changes in optical and chemical properties of tar ball aerosols by atmospheric photochemical aging |
title_full_unstemmed |
Dynamic changes in optical and chemical properties of tar ball aerosols by atmospheric photochemical aging |
title_sort |
dynamic changes in optical and chemical properties of tar ball aerosols by atmospheric photochemical aging |
publisher |
Copernicus Publications |
series |
Atmospheric Chemistry and Physics |
issn |
1680-7316 1680-7324 |
publishDate |
2019-01-01 |
description |
<p>Following wood pyrolysis, tar ball aerosols were laboratory generated from
wood tar separated into polar and nonpolar phases. Chemical information of
fresh tar balls was obtained from a high-resolution time-of-flight aerosol
mass spectrometer (HR-ToF-AMS) and single-particle laser desorption/resonance
enhanced multiphoton ionization mass spectrometry (SP-LD-REMPI-MS). Their
continuous refractive index (RI) between 365 and 425 nm was retrieved using
a broadband cavity enhanced spectroscopy (BBCES). Dynamic changes in the
optical and chemical properties for the nonpolar tar ball aerosols in
<span class="inline-formula">NO<sub><i>x</i></sub></span>-dependent photochemical process were investigated in an
oxidation flow reactor (OFR). Distinct differences in the chemical
composition of the fresh polar and nonpolar tar aerosols were identified.
Nonpolar tar aerosols contain predominantly high-molecular weight
unsubstituted and alkyl-substituted polycylic aromatic hydrocarbons (PAHs),
while polar tar aerosols consist of a high number of oxidized aromatic
substances (e.g., methoxy-phenols, benzenediol) with higher O : C ratios
and carbon oxidation states. Fresh tar balls have light absorption
characteristics similar to atmospheric brown carbon (BrC) aerosol with higher
absorption efficiency towards the UV wavelengths. The average retrieved RI is
<span class="inline-formula">1.661+0.020<i>i</i></span> and <span class="inline-formula">1.635+0.003<i>i</i></span> for the nonpolar and polar tar aerosols,
respectively, with an absorption Ångström exponent (AAE) between 5.7
and 7.8 in the detected wavelength range. The RI fits a volume mixing rule
for internally mixed nonpolar/polar tar balls. The RI of the tar ball
aerosols decreased with increasing wavelength under photochemical oxidation.
Photolysis by UV light (254 nm), without strong oxidants in the system,
slightly decreased the RI and increased the oxidation state of the tar balls.
Oxidation under varying OH exposure levels and in the absence of
<span class="inline-formula">NO<sub><i>x</i></sub></span> diminished the absorption (bleaching) and increased the
O : C ratio of the tar balls. The photobleaching via OH radical initiated
oxidation is mainly attributed to decomposition of chromophoric aromatics,
nitrogen-containing organics, and high-molecular weight components in the
aged particles. Photolysis of nitrous oxide (<span class="inline-formula">N<sub>2</sub>O</span>) was used to
simulate <span class="inline-formula">NO<sub><i>x</i></sub></span>-dependent photochemical aging of tar balls in
the OFR. Under high-<span class="inline-formula">NO<sub><i>x</i></sub></span> conditions with similar OH exposure,
photochemical aging led to the formation of organic nitrates, and increased
both oxidation degree and light absorption for the aged tar ball aerosols.
These observations suggest that secondary organic nitrate formation
counteracts the bleaching by OH radical photooxidation to eventually regain
some absorption of the aged tar ball aerosols. The atmospheric implication
and climate effects from tar balls upon various oxidation processes are
briefly discussed.</p> |
url |
https://www.atmos-chem-phys.net/19/139/2019/acp-19-139-2019.pdf |
work_keys_str_mv |
AT cli dynamicchangesinopticalandchemicalpropertiesoftarballaerosolsbyatmosphericphotochemicalaging AT qhe dynamicchangesinopticalandchemicalpropertiesoftarballaerosolsbyatmosphericphotochemicalaging AT jschade dynamicchangesinopticalandchemicalpropertiesoftarballaerosolsbyatmosphericphotochemicalaging AT jpassig dynamicchangesinopticalandchemicalpropertiesoftarballaerosolsbyatmosphericphotochemicalaging AT jpassig dynamicchangesinopticalandchemicalpropertiesoftarballaerosolsbyatmosphericphotochemicalaging AT rzimmermann dynamicchangesinopticalandchemicalpropertiesoftarballaerosolsbyatmosphericphotochemicalaging AT rzimmermann dynamicchangesinopticalandchemicalpropertiesoftarballaerosolsbyatmosphericphotochemicalaging AT dmeidan dynamicchangesinopticalandchemicalpropertiesoftarballaerosolsbyatmosphericphotochemicalaging AT alaskin dynamicchangesinopticalandchemicalpropertiesoftarballaerosolsbyatmosphericphotochemicalaging AT yrudich dynamicchangesinopticalandchemicalpropertiesoftarballaerosolsbyatmosphericphotochemicalaging |
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1725845621009547264 |
spelling |
doaj-6b5f21fc5d7d4cb68774fe2fd9cecd3d2020-11-24T22:00:04ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242019-01-011913916310.5194/acp-19-139-2019Dynamic changes in optical and chemical properties of tar ball aerosols by atmospheric photochemical agingC. Li0Q. He1J. Schade2J. Passig3J. Passig4R. Zimmermann5R. Zimmermann6D. Meidan7A. Laskin8Y. Rudich9Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot 76100, IsraelDepartment of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot 76100, IsraelJoint Mass Spectrometry Centre, University of Rostock, Dr.-Lorenz-Weg 2, 18059 Rostock, GermanyJoint Mass Spectrometry Centre, University of Rostock, Dr.-Lorenz-Weg 2, 18059 Rostock, GermanyJoint Mass Spectrometry Centre, Cooperation Group “Comprehensive Molecular Analytics” (CMA), Helmholtz Zentrum München, Ingolstädter Landstrasse 1, 85764 Neuherberg, GermanyJoint Mass Spectrometry Centre, University of Rostock, Dr.-Lorenz-Weg 2, 18059 Rostock, GermanyJoint Mass Spectrometry Centre, Cooperation Group “Comprehensive Molecular Analytics” (CMA), Helmholtz Zentrum München, Ingolstädter Landstrasse 1, 85764 Neuherberg, GermanyDepartment of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot 76100, IsraelDepartment of Chemistry, Purdue University, West Lafayette, Indiana 47907, USADepartment of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot 76100, Israel<p>Following wood pyrolysis, tar ball aerosols were laboratory generated from wood tar separated into polar and nonpolar phases. Chemical information of fresh tar balls was obtained from a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and single-particle laser desorption/resonance enhanced multiphoton ionization mass spectrometry (SP-LD-REMPI-MS). Their continuous refractive index (RI) between 365 and 425 nm was retrieved using a broadband cavity enhanced spectroscopy (BBCES). Dynamic changes in the optical and chemical properties for the nonpolar tar ball aerosols in <span class="inline-formula">NO<sub><i>x</i></sub></span>-dependent photochemical process were investigated in an oxidation flow reactor (OFR). Distinct differences in the chemical composition of the fresh polar and nonpolar tar aerosols were identified. Nonpolar tar aerosols contain predominantly high-molecular weight unsubstituted and alkyl-substituted polycylic aromatic hydrocarbons (PAHs), while polar tar aerosols consist of a high number of oxidized aromatic substances (e.g., methoxy-phenols, benzenediol) with higher O : C ratios and carbon oxidation states. Fresh tar balls have light absorption characteristics similar to atmospheric brown carbon (BrC) aerosol with higher absorption efficiency towards the UV wavelengths. The average retrieved RI is <span class="inline-formula">1.661+0.020<i>i</i></span> and <span class="inline-formula">1.635+0.003<i>i</i></span> for the nonpolar and polar tar aerosols, respectively, with an absorption Ångström exponent (AAE) between 5.7 and 7.8 in the detected wavelength range. The RI fits a volume mixing rule for internally mixed nonpolar/polar tar balls. The RI of the tar ball aerosols decreased with increasing wavelength under photochemical oxidation. Photolysis by UV light (254 nm), without strong oxidants in the system, slightly decreased the RI and increased the oxidation state of the tar balls. Oxidation under varying OH exposure levels and in the absence of <span class="inline-formula">NO<sub><i>x</i></sub></span> diminished the absorption (bleaching) and increased the O : C ratio of the tar balls. The photobleaching via OH radical initiated oxidation is mainly attributed to decomposition of chromophoric aromatics, nitrogen-containing organics, and high-molecular weight components in the aged particles. Photolysis of nitrous oxide (<span class="inline-formula">N<sub>2</sub>O</span>) was used to simulate <span class="inline-formula">NO<sub><i>x</i></sub></span>-dependent photochemical aging of tar balls in the OFR. Under high-<span class="inline-formula">NO<sub><i>x</i></sub></span> conditions with similar OH exposure, photochemical aging led to the formation of organic nitrates, and increased both oxidation degree and light absorption for the aged tar ball aerosols. These observations suggest that secondary organic nitrate formation counteracts the bleaching by OH radical photooxidation to eventually regain some absorption of the aged tar ball aerosols. The atmospheric implication and climate effects from tar balls upon various oxidation processes are briefly discussed.</p>https://www.atmos-chem-phys.net/19/139/2019/acp-19-139-2019.pdf |