Transport-driven aerosol differences above and below the canopy of a mixed deciduous forest

<p>Exchanges of energy and mass between the surrounding air and plant surfaces occur below, within, and above a forest's vegetative canopy. The canopy also can lead to vertical gradients in light, trace gases, oxidant availability, turbulent mixing, and properties and concentrations of or...

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Autores principales:	A. A. T. Bui, H. W. Wallace, S. Kavassalis, H. D. Alwe, J. H. Flynn, M. H. Erickson, S. Alvarez, D. B. Millet, A. L. Steiner, R. J. Griffin
Formato:	article
Lenguaje:	EN
Publicado:	Copernicus Publications 2021
Materias:	Physics QC1-999 Chemistry QD1-999
Acceso en línea:	https://doaj.org/article/4b44fcfba9b74e1aa91f651bb2c398b7
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spelling	oai:doaj.org-article:4b44fcfba9b74e1aa91f651bb2c398b72021-11-24T11:23:08ZTransport-driven aerosol differences above and below the canopy of a mixed deciduous forest10.5194/acp-21-17031-20211680-73161680-7324https://doaj.org/article/4b44fcfba9b74e1aa91f651bb2c398b72021-11-01T00:00:00Zhttps://acp.copernicus.org/articles/21/17031/2021/acp-21-17031-2021.pdfhttps://doaj.org/toc/1680-7316https://doaj.org/toc/1680-7324<p>Exchanges of energy and mass between the surrounding air and plant surfaces occur below, within, and above a forest's vegetative canopy. The canopy also can lead to vertical gradients in light, trace gases, oxidant availability, turbulent mixing, and properties and concentrations of organic aerosol (OA). In this study, a high-resolution time-of-flight aerosol mass spectrometer was used to measure non-refractory submicron aerosol composition and concentration above (30 m) and below (6 m) a forest canopy in a mixed deciduous forest at the Program for Research on Oxidants: PHotochemistry, Emissions, and Transport tower in northern Michigan during the summer of 2016. Three OA factors are resolved using positive matrix factorization: more-oxidized oxygenated organic aerosol (MO-OOA), isoprene-epoxydiol-derived organic aerosol (IEPOX-OA), and 91Fac (a factor characterized with a distinct fragment ion at <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>m</mi><mo>/</mo><mi>z</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="23pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="91270dba487782af7360c80516416e4b"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-17031-2021-ie00001.svg" width="23pt" height="14pt" src="acp-21-17031-2021-ie00001.png"/></svg:svg></span></span> 91) from both the above- and the below-canopy inlets. MO-OOA was most strongly associated with long-range transport from more polluted regions to the south, while IEPOX-OA and 91Fac were associated with shorter-range transport and local oxidation chemistry. Overall vertical similarity in aerosol composition, degrees of oxidation, and diurnal profiles between the two inlets was observed throughout the campaign, which implies that rapid in-canopy transport of aerosols is efficient enough to cause relatively consistent vertical distributions of aerosols at this scale. However, four distinct vertical gradient episodes are identified for OA, with vertical concentration differences (above-canopy minus below-canopy concentrations) in total OA of up to 0.8 <span class="inline-formula">µ</span>g m<span class="inline-formula"><sup>−3</sup></span>, a value that is 42 % of the campaign average OA concentration of 1.9 <span class="inline-formula">µ</span>g m<span class="inline-formula"><sup>−3</sup></span>. The magnitude of these differences correlated with concurrent vertical differences in either sulfate aerosol or ozone. These differences are likely driven by a combination of long-range transport mechanisms, canopy-scale mixing, and local chemistry. These results emphasize the importance of including vertical and horizontal transport mechanisms when interpreting trace gas and aerosol data in forested environments.</p>A. A. T. BuiH. W. WallaceH. W. WallaceS. KavassalisH. D. AlweJ. H. FlynnM. H. EricksonM. H. EricksonS. AlvarezD. B. MilletA. L. SteinerR. J. GriffinR. J. GriffinCopernicus PublicationsarticlePhysicsQC1-999ChemistryQD1-999ENAtmospheric Chemistry and Physics, Vol 21, Pp 17031-17050 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Physics QC1-999 Chemistry QD1-999
spellingShingle	Physics QC1-999 Chemistry QD1-999 A. A. T. Bui H. W. Wallace H. W. Wallace S. Kavassalis H. D. Alwe J. H. Flynn M. H. Erickson M. H. Erickson S. Alvarez D. B. Millet A. L. Steiner R. J. Griffin R. J. Griffin Transport-driven aerosol differences above and below the canopy of a mixed deciduous forest
description	<p>Exchanges of energy and mass between the surrounding air and plant surfaces occur below, within, and above a forest's vegetative canopy. The canopy also can lead to vertical gradients in light, trace gases, oxidant availability, turbulent mixing, and properties and concentrations of organic aerosol (OA). In this study, a high-resolution time-of-flight aerosol mass spectrometer was used to measure non-refractory submicron aerosol composition and concentration above (30 m) and below (6 m) a forest canopy in a mixed deciduous forest at the Program for Research on Oxidants: PHotochemistry, Emissions, and Transport tower in northern Michigan during the summer of 2016. Three OA factors are resolved using positive matrix factorization: more-oxidized oxygenated organic aerosol (MO-OOA), isoprene-epoxydiol-derived organic aerosol (IEPOX-OA), and 91Fac (a factor characterized with a distinct fragment ion at <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>m</mi><mo>/</mo><mi>z</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="23pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="91270dba487782af7360c80516416e4b"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-17031-2021-ie00001.svg" width="23pt" height="14pt" src="acp-21-17031-2021-ie00001.png"/></svg:svg></span></span> 91) from both the above- and the below-canopy inlets. MO-OOA was most strongly associated with long-range transport from more polluted regions to the south, while IEPOX-OA and 91Fac were associated with shorter-range transport and local oxidation chemistry. Overall vertical similarity in aerosol composition, degrees of oxidation, and diurnal profiles between the two inlets was observed throughout the campaign, which implies that rapid in-canopy transport of aerosols is efficient enough to cause relatively consistent vertical distributions of aerosols at this scale. However, four distinct vertical gradient episodes are identified for OA, with vertical concentration differences (above-canopy minus below-canopy concentrations) in total OA of up to 0.8 <span class="inline-formula">µ</span>g m<span class="inline-formula"><sup>−3</sup></span>, a value that is 42 % of the campaign average OA concentration of 1.9 <span class="inline-formula">µ</span>g m<span class="inline-formula"><sup>−3</sup></span>. The magnitude of these differences correlated with concurrent vertical differences in either sulfate aerosol or ozone. These differences are likely driven by a combination of long-range transport mechanisms, canopy-scale mixing, and local chemistry. These results emphasize the importance of including vertical and horizontal transport mechanisms when interpreting trace gas and aerosol data in forested environments.</p>
format	article
author	A. A. T. Bui H. W. Wallace H. W. Wallace S. Kavassalis H. D. Alwe J. H. Flynn M. H. Erickson M. H. Erickson S. Alvarez D. B. Millet A. L. Steiner R. J. Griffin R. J. Griffin
author_facet	A. A. T. Bui H. W. Wallace H. W. Wallace S. Kavassalis H. D. Alwe J. H. Flynn M. H. Erickson M. H. Erickson S. Alvarez D. B. Millet A. L. Steiner R. J. Griffin R. J. Griffin
author_sort	A. A. T. Bui
title	Transport-driven aerosol differences above and below the canopy of a mixed deciduous forest
title_short	Transport-driven aerosol differences above and below the canopy of a mixed deciduous forest
title_full	Transport-driven aerosol differences above and below the canopy of a mixed deciduous forest
title_fullStr	Transport-driven aerosol differences above and below the canopy of a mixed deciduous forest
title_full_unstemmed	Transport-driven aerosol differences above and below the canopy of a mixed deciduous forest
title_sort	transport-driven aerosol differences above and below the canopy of a mixed deciduous forest
publisher	Copernicus Publications
publishDate	2021
url	https://doaj.org/article/4b44fcfba9b74e1aa91f651bb2c398b7
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Transport-driven aerosol differences above and below the canopy of a mixed deciduous forest

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