Distributions and sources of low-molecular-weight monocarboxylic acids in gas and particles from a deciduous broadleaf forest in northern Japan
<p>To better understand the distributions and sources of low-molecular-weight (LMW) monocarboxylic acids (monoacids) in the forest atmosphere, we conducted simultaneous collection of gaseous and particulate samples at a deciduous broadleaf forest site in northern Japan. LMW normal (C<span c...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-02-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/19/2421/2019/acp-19-2421-2019.pdf |
| Summary: | <p>To better understand the distributions and sources of
low-molecular-weight (LMW) monocarboxylic acids (monoacids) in the forest
atmosphere, we conducted simultaneous collection of gaseous and particulate
samples at a deciduous broadleaf forest site in northern Japan. LMW normal
(C<span class="inline-formula"><sub>1</sub></span>–C<span class="inline-formula"><sub>10</sub></span>), branched (iC<span class="inline-formula"><sub>4</sub></span>–iC<span class="inline-formula"><sub>6</sub></span>), hydroxyl (glycolic and
lactic) and aromatic (benzoic) monoacids were detected in the gas and
particle phases. The dominant LMW monoacids in gas phase were formic (mean:
953 ng m<span class="inline-formula"><sup>−3</sup></span>) and acetic (528 ng m<span class="inline-formula"><sup>−3</sup></span>) acids followed by propionic
(37 ng m<span class="inline-formula"><sup>−3</sup></span>) or isopentanoic (42 ng m<span class="inline-formula"><sup>−3</sup></span>) acid. In the particle
phase, isopentanoic (159 ng m<span class="inline-formula"><sup>−3</sup></span>) was dominant, followed by acetic
(104 ng m<span class="inline-formula"><sup>−3</sup></span>) and formic (71 ng m<span class="inline-formula"><sup>−3</sup></span>) or lactic
(65 ng m<span class="inline-formula"><sup>−3</sup></span>) acids. Concentrations of LMW monoacids did not show
correlations with anthropogenic tracers such as nss-<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M13" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">SO</mi><mn mathvariant="normal">4</mn><mrow><mn mathvariant="normal">2</mn><mo>-</mo></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="29pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="2216394d525831533871aea4983d93c3"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-2421-2019-ie00001.svg" width="29pt" height="17pt" src="acp-19-2421-2019-ie00001.png"/></svg:svg></span></span> and
<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M14" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">NO</mi><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="25pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="c5e3e0772eea57309f236de17ca43cb8"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-2421-2019-ie00002.svg" width="25pt" height="16pt" src="acp-19-2421-2019-ie00002.png"/></svg:svg></span></span>, indicating that anthropogenic contribution is not important.
Concentrations of C<span class="inline-formula"><sub>1</sub></span>–C<span class="inline-formula"><sub>6</sub></span> monoacids in the gas phase showed positive
correlations (<span class="inline-formula"><i>r</i><sup>2</sup>=0.21</span>–0.91) with isobutyric acid (iC<span class="inline-formula"><sub>4</sub></span>), which
may be produced by microbial activity in soil. The forest soil may be a
source of gaseous C<span class="inline-formula"><sub>1</sub></span>–C<span class="inline-formula"><sub>6</sub></span> monoacids in the forest atmosphere. Acetic
acid in the particle phase positively correlated with nonanoic acid (C<span class="inline-formula"><sub>9</sub></span>)
(<span class="inline-formula"><i>r</i><sup>2</sup>=0.63</span>), suggesting that formation of acetic and nonanoic acids is
associated with the oxidation of biogenic unsaturated fatty acids in the
aerosol phase, in addition to photochemical oxidation of biogenic volatile
organic compounds. The particle-phase fractions (<span class="inline-formula"><i>F</i><sub>p</sub></span>) of formic
and acetic acids showed negative correlation with ambient temperature
(C<span class="inline-formula"><sub>1</sub></span>: <span class="inline-formula"><i>r</i><sup>2</sup>=0.49</span>, C<span class="inline-formula"><sub>2</sub></span>: <span class="inline-formula"><i>r</i><sup>2</sup>=0.60</span>) but showed positive
correlation with relative humidity (C<span class="inline-formula"><sub>1</sub></span>: <span class="inline-formula"><i>r</i><sup>2</sup>=0.30</span>, C<span class="inline-formula"><sub>2</sub></span>: <span class="inline-formula"><i>r</i><sup>2</sup>=0.55</span>) in daytime, suggesting that these meteorological parameters are
important for the gas and particle portioning of monoacids in the forest
atmosphere.</p> |
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| ISSN: | 1680-7316 1680-7324 |