Tropical tropospheric aerosol sources and chemical composition observed at high altitude in the Bolivian Andes
<p><span id="page2838"/>The chemical composition of PM<span class="inline-formula"><sub>10</sub></span> and non-overlapping PM<span class="inline-formula"><sub>2.5</sub></span> was studied at the summit of Mt....
| Main Authors: | , , , , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2024-03-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/24/2837/2024/acp-24-2837-2024.pdf |
| Summary: | <p><span id="page2838"/>The chemical composition of PM<span class="inline-formula"><sub>10</sub></span> and non-overlapping PM<span class="inline-formula"><sub>2.5</sub></span> was studied at the summit of Mt. Chacaltaya (5380 m a.s.l., lat. <span class="inline-formula">−</span>16.346950°, long. <span class="inline-formula">−</span>68.128250°) providing a unique long-term record spanning from December 2011 to March 2020. The chemical composition of aerosol at the Chacaltaya Global Atmosphere Watch (GAW) site is representative of the regional background, seasonally affected by biomass burning practices and by nearby anthropogenic emissions from the metropolitan area of La Paz–El Alto. Concentration levels are clearly influenced by seasons with minima occurring during the wet season (December to March) and maxima occurring during the dry and transition seasons (April to November). Ions, total carbon (EC <span class="inline-formula">+</span> OC), and saccharide interquartile ranges for concentrations are 558–1785, 384–1120, and 4.3–25.5 ng m<span class="inline-formula"><sup>−3</sup></span> for bulk PM<span class="inline-formula"><sub>10</sub></span> and 917–2308, 519–1175, and 3.9–24.1 ng m<span class="inline-formula"><sup>−3</sup></span> for PM<span class="inline-formula"><sub>2.5</sub></span>, respectively, with most of the aerosol seemingly present in the PM<span class="inline-formula"><sub>2.5</sub></span> fraction. Such concentrations are overall lower compared to other high-altitude stations around the globe but higher than Amazonian remote sites (except for OC). For PM<span class="inline-formula"><sub>10</sub></span>, there is dominance of insoluble mineral matter (33 %–56 % of the mass), organic matter (7 %–34 %), and secondary inorganic aerosol (15 %–26 %). Chemical composition profiles were identified for different origins: EC, NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M12" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="9pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="ee54bb0fff66afdafaf51bed1fde360d"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-24-2837-2024-ie00001.svg" width="9pt" height="16pt" src="acp-24-2837-2024-ie00001.png"/></svg:svg></span></span>, NH<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M13" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">4</mn><mo>+</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="f1ca5762abf079d28af10bf21d382d4c"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-24-2837-2024-ie00002.svg" width="8pt" height="15pt" src="acp-24-2837-2024-ie00002.png"/></svg:svg></span></span>, glucose, and C<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M15" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><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="13pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="9def59c1763723bf85d4c029a1ebd14e"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-24-2837-2024-ie00003.svg" width="13pt" height="17pt" src="acp-24-2837-2024-ie00003.png"/></svg:svg></span></span> for the nearby urban and rural areas; OC, EC, NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M16" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="9pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="06954914259a113e7faaa0d01a8ee756"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-24-2837-2024-ie00004.svg" width="9pt" height="16pt" src="acp-24-2837-2024-ie00004.png"/></svg:svg></span></span>, K<span class="inline-formula"><sup>+</sup></span>, acetate, formate, levoglucosan, and some F<span class="inline-formula"><sup>−</sup></span> and Br<span class="inline-formula"><sup>−</sup></span> for biomass burning; MeSO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M20" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="9pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="9a17d6ab4c67d7f6701d29ccd0703b2e"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-24-2837-2024-ie00005.svg" width="9pt" height="16pt" src="acp-24-2837-2024-ie00005.png"/></svg:svg></span></span>, Na<span class="inline-formula"><sup>+</sup></span>, Mg<span class="inline-formula"><sup>2+</sup></span>, K<span class="inline-formula"><sup>+</sup></span>, and Ca<span class="inline-formula"><sup>2+</sup></span> for aged marine emissions from the Pacific Ocean; arabitol, mannitol, and glucose for biogenic emissions; Na<span class="inline-formula"><sup>+</sup></span>, Ca<span class="inline-formula"><sup>2+</sup></span>, Mg<span class="inline-formula"><sup>2+</sup></span>, and K<span class="inline-formula"><sup>+</sup></span> for soil dust; and SO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M29" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><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="13pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="29af680a2c2c3e13b3242191be5b1002"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-24-2837-2024-ie00006.svg" width="13pt" height="17pt" src="acp-24-2837-2024-ie00006.png"/></svg:svg></span></span>, F<span class="inline-formula"><sup>−</sup></span>, and some Cl<span class="inline-formula"><sup>−</sup></span> for volcanism. Regional biomass burning practices influence the soluble fraction of the aerosol between June and November. The organic fraction is present all year round and has both anthropogenic (biomass burning and other combustion sources) and natural (primary and secondary biogenic emissions) origins, with the <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M32" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi mathvariant="normal">OC</mi><mo>/</mo><mi mathvariant="normal">EC</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="40pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="de7a86866b2e8a9da956d9c46cef780c"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-24-2837-2024-ie00007.svg" width="40pt" height="14pt" src="acp-24-2837-2024-ie00007.png"/></svg:svg></span></span> mass ratio being practically constant all year round (10.5 <span class="inline-formula">±</span> 5.7, IQR 8.1–13.3). Peruvian volcanism has dominated the SO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M34" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><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="13pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="23ee1f08807182dc6cd06a1b188c59a7"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-24-2837-2024-ie00008.svg" width="13pt" height="17pt" src="acp-24-2837-2024-ie00008.png"/></svg:svg></span></span> concentration since 2014, though it presents strong temporal variability due to the intermittence of the sources and seasonal changes in the transport patterns. These measurements represent some of the first long-term observations of aerosol chemical composition at a continental high-altitude site in the tropical Southern Hemisphere.</p> |
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| ISSN: | 1680-7316 1680-7324 |