Enhancing characterization of organic nitrogen components in aerosols and droplets using high-resolution aerosol mass spectrometry
<p>This study aims to enhance the understanding and application of the Aerodyne high-resolution aerosol mass spectrometer (HR-AMS) for the comprehensive characterization of organic nitrogen (<span class="inline-formula">ON</span>) compounds in aerosol particles and atmosp...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2024-01-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://amt.copernicus.org/articles/17/423/2024/amt-17-423-2024.pdf |
| Summary: | <p>This study aims to enhance the understanding and application of the Aerodyne high-resolution aerosol mass spectrometer (HR-AMS) for the comprehensive characterization of organic nitrogen (<span class="inline-formula">ON</span>) compounds in aerosol particles and atmospheric droplets. To achieve this goal, we analyzed 75 <span class="inline-formula">N</span>-containing organic compounds, representing a diverse range of ambient non-organonitrate ON (NOON) types, including amines, amides, amino acids, <span class="inline-formula">N</span> heterocycles, protein, and humic acids. Our results show that NOON compounds can produce significant levels of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">NH</mi><mi>x</mi><mo>+</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="24pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="109c69e71ff23ae7ccceca2ac1c708ff"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-17-423-2024-ie00001.svg" width="24pt" height="14pt" src="amt-17-423-2024-ie00001.png"/></svg:svg></span></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M5" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">NO</mi><mi>x</mi><mo>+</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="24pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="028ac11a5d00255f5cd2bebfa53fb902"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-17-423-2024-ie00002.svg" width="24pt" height="14pt" src="amt-17-423-2024-ie00002.png"/></svg:svg></span></span> ion fragments, which are typically recognized as ions representative of inorganic nitrogen species. We also identified the presence of <span class="inline-formula">CH<sub>2</sub>N<sup>+</sup></span> at <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M7" 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="82359dc0e2bbce7906032009eb1b5089"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-17-423-2024-ie00003.svg" width="23pt" height="14pt" src="amt-17-423-2024-ie00003.png"/></svg:svg></span></span> <span class="inline-formula">=</span> 28.0187, an ion fragment rarely quantified in ambient datasets due to substantial interference from <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M9" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">N</mi><mn mathvariant="normal">2</mn><mo>+</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="16pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="652e67b731236e9e6b59191f38018732"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-17-423-2024-ie00004.svg" width="16pt" height="15pt" src="amt-17-423-2024-ie00004.png"/></svg:svg></span></span>. As a result, the utilization of an updated calibration factor of 0.79 is necessary for accurate NOON quantification via the HR-AMS. We also assessed the relative ionization efficiencies (RIEs) for various NOON species and found that the average RIE for NOON compounds (1.52 <span class="inline-formula">±</span> 0.58) aligns with the commonly used default value of 1.40 for organic aerosol. Moreover, through a careful examination of the HR-AMS mass spectral features of various NOON types, we propose fingerprint ion series that can aid the NOON speciation analysis. For instance, the presence of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M11" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msub><mi mathvariant="normal">C</mi><mi>n</mi></msub><msub><mi mathvariant="normal">H</mi><mrow><mn mathvariant="normal">2</mn><mi>n</mi><mo>+</mo><mn mathvariant="normal">2</mn></mrow></msub><msup><mi mathvariant="normal">N</mi><mo>+</mo></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="56pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="fc2232c7321250cabd8bb3e785ce7f4d"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-17-423-2024-ie00005.svg" width="56pt" height="14pt" src="amt-17-423-2024-ie00005.png"/></svg:svg></span></span> ions is closely linked with amines, with <span class="inline-formula">CH<sub>4</sub>N<sup>+</sup></span> indicating primary amines, <span class="inline-formula">C<sub>2</sub>H<sub>6</sub>N<sup>+</sup></span> suggesting secondary amines, and <span class="inline-formula">C<sub>3</sub>H<sub>8</sub>N<sup>+</sup></span> representing tertiary amines. <span class="inline-formula">C<sub><i>n</i></sub>H<sub>2<i>n</i></sub>NO<sup>+</sup></span> ions (especially for <span class="inline-formula"><i>n</i></span> values of 1–4) are very likely derived from amides. The co-existence of three ions, <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M17" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msub><mi mathvariant="normal">C</mi><mn mathvariant="normal">2</mn></msub><msub><mi mathvariant="normal">H</mi><mn mathvariant="normal">4</mn></msub><msubsup><mi mathvariant="normal">NO</mi><mn mathvariant="normal">2</mn><mo>+</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="50pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="4ff6666caf854b8daca7ecc73fffd2a2"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-17-423-2024-ie00006.svg" width="50pt" height="15pt" src="amt-17-423-2024-ie00006.png"/></svg:svg></span></span>, <span class="inline-formula">C<sub>2</sub>H<sub>3</sub>NO<sup>+</sup></span>, and <span class="inline-formula">CH<sub>4</sub>NO<sup>+</sup></span>, serves as an indicator for the presence of amino acids. Additionally, the presence of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M20" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msub><mi mathvariant="normal">C</mi><mi>x</mi></msub><msub><mi mathvariant="normal">H</mi><mi>y</mi></msub><msubsup><mi mathvariant="normal">N</mi><mn mathvariant="normal">2</mn><mo>+</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="42pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="cabf41e55f333f84ea7943c3040185a0"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-17-423-2024-ie00007.svg" width="42pt" height="16pt" src="amt-17-423-2024-ie00007.png"/></svg:svg></span></span> ions indicates the occurrence of 2<span class="inline-formula">N</span>-heterocyclic compounds. Notably, an elevated abundance of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M22" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">NH</mi><mn mathvariant="normal">4</mn><mo>+</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="24pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="44642da34e3da1fffc83c720c465c894"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-17-423-2024-ie00008.svg" width="24pt" height="15pt" src="amt-17-423-2024-ie00008.png"/></svg:svg></span></span> is a distinct signature for amines and amino acids, as inorganic ammonium salts produce only negligible amounts of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M23" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">NH</mi><mn mathvariant="normal">4</mn><mo>+</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="24pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="7e9bce7dd5b43b642d42082f2f6f1206"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-17-423-2024-ie00009.svg" width="24pt" height="15pt" src="amt-17-423-2024-ie00009.png"/></svg:svg></span></span> in the HR-AMS.</p>
<p>Finally, we quantified the NOON contents in submicron particles (<span class="inline-formula">PM<sub>1</sub></span>) and fog water in Fresno, California, and <span class="inline-formula">PM<sub>1</sub></span> in New York City (NYC). Our results revealed the substantial presence of amino compounds in both Fresno and NYC aerosols, whereas concurrently collected fog water in Fresno contained a broader range of NOON species, including <span class="inline-formula">N</span>-containing aromatic heterocycle (e.g., imidazoles) and amides. These findings highlight the significant potential of employing the widespread HR-AMS measurements of ambient aerosols and droplets to enhance our understanding of the sources, transformation processes, and environmental impacts associated with NOON compounds in the atmosphere.</p> |
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| ISSN: | 1867-1381 1867-8548 |