Technical note: Chemical composition and source identification of fluorescent components in atmospheric water-soluble brown carbon by excitation–emission matrix spectroscopy with parallel factor analysis – potential limitations and applications
<p>Three-dimensional excitation–emission matrix (EEM) fluorescence spectroscopy is an important method for the identification of the occurrence, chemical composition, and source of atmospheric chromophores. However, current knowledge on the identification and interpretation of fluorescent comp...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-02-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/23/2613/2023/acp-23-2613-2023.pdf |
| Summary: | <p>Three-dimensional excitation–emission matrix (EEM) fluorescence spectroscopy
is an important method for the identification of the occurrence, chemical
composition, and source of atmospheric chromophores. However, current
knowledge on the identification and interpretation of fluorescent components
is mainly based on aquatic dissolved organic matter and might not be
applicable to atmospheric samples. Therefore, this study comprehensively
investigated EEM data of different types of strong light-absorbing organic
compounds, water-soluble organic matter (WSOM) in different aerosol samples
(combustion source samples and ambient aerosols), soil dust, and purified
fulvic and humic acids supplemented by parallel factor (PARAFAC) modeling.
The results demonstrated that organic compounds with high aromaticity and
strong electron-donating groups generally present strong fluorescence
spectra at longer emission wavelengths, whereas organic compounds
substituted with electron-withdrawing groups have relatively weaker
fluorescence intensity. In particular, aromatic compounds containing nitro
groups (i.e., nitrophenols), which show strong absorption and are the major
component of atmospheric brown carbon, exhibited no significant
fluorescence. The EEM–PARAFAC method identified three fluorescent components (i.e., C1,
C2, and C3) in ambient WSOM. Although EEM–PARAFAC-derived C1 (Ex<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="1b4178c77ca0d4bfee6c9ddd864f3a43"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-23-2613-2023-ie00001.svg" width="8pt" height="14pt" src="acp-23-2613-2023-ie00001.png"/></svg:svg></span></span>Em <span class="inline-formula">=</span> 235, <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">270</mn><mo>/</mo><mn mathvariant="normal">330</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="45pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="4095a45018ee4f06801f0232da2e1364"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-23-2613-2023-ie00002.svg" width="45pt" height="14pt" src="acp-23-2613-2023-ie00002.png"/></svg:svg></span></span> nm) in ambient WSOM is generally considered to be protein-like groups, our
findings suggested that it is mainly composed of aromatic acids, phenolic
compounds, and their derivatives, with only traces of amino acids. C2 is
associated with the atmospheric chemical reaction of biomass burning and/or
biogenic organic molecules, with a relatively lower degree of oxidation, which
are more abundant in Guangzhou WSOM (56 %–69 %). C3, in contrast, is mainly
attributed to highly oxygenated organic molecules derived from soil and
atmospheric aging processes and has a relatively higher contribution in
Chuzhou WSOM (23 %). These findings provide new insights into the analysis
of chemical properties and sources of atmospheric fluorophores using the EEM
method.</p> |
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| ISSN: | 1680-7316 1680-7324 |