Technical note: Measurement of chemically resolved volume equivalent diameter and effective density of particles by AAC-SPAMS
oleh: L. Peng, L. Peng, L. Li, G. Zhang, G. Zhang, X. Du, X. Wang, X. Wang, P. Peng, P. Peng, G. Sheng, X. Bi, X. Bi
| Format: | Article |
|---|---|
| Diterbitkan: | Copernicus Publications 2021-04-01 |
Deskripsi
<p>Size and effective density (<span class="inline-formula"><i>ρ</i><sub>e</sub></span>) are important properties of aerosol particles and are related to their influences on human health and the global climate. The volume equivalent diameter (<span class="inline-formula"><i>D</i><sub>ve</sub></span>) is an intrinsic property that is used to evaluate particle size. Three definitions of <span class="inline-formula"><i>ρ</i><sub>e</sub></span> are generally used to characterize the physical property of a particle as an alternative to particle density, in which only the <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi mathvariant="italic">ρ</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">II</mi></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="14pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="1a17b9e0552e0e7c3fdb2931431fe114"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-5605-2021-ie00001.svg" width="14pt" height="16pt" src="acp-21-5605-2021-ie00001.png"/></svg:svg></span></span>, defined as the ratio of particle density (<span class="inline-formula"><i>ρ</i><sub>p</sub></span>) to a dynamic shape factor (<span class="inline-formula"><i>χ</i></span>), has the characteristic of being independent of particle size. However, it is still challenging to simultaneously characterize the <span class="inline-formula"><i>D</i><sub>ve</sub></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi mathvariant="italic">ρ</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">II</mi></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="14pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="9fefa5b72e47e5fd2a78d03cf2677c7a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-5605-2021-ie00002.svg" width="14pt" height="16pt" src="acp-21-5605-2021-ie00002.png"/></svg:svg></span></span> of aspherical particles. Here, we present a novel system that classifies particles with their aerodynamic diameter (<span class="inline-formula"><i>D</i><sub>a</sub></span>) by aerodynamic aerosol classifier (AAC) and determines their vacuum aerodynamic diameter (<span class="inline-formula"><i>D</i><sub>va</sub></span>) by single-particle aerosol mass spectrometry (SPAMS) to achieve a measurement of <span class="inline-formula"><i>D</i><sub>ve</sub></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M12" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi mathvariant="italic">ρ</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">II</mi></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="14pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="62b1dfcd2e48a9ed55bc4e1301c3dc4b"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-5605-2021-ie00003.svg" width="14pt" height="16pt" src="acp-21-5605-2021-ie00003.png"/></svg:svg></span></span>. The reliability of the AAC-SPAMS system for accurately obtaining <span class="inline-formula"><i>D</i><sub>ve</sub></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M14" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi mathvariant="italic">ρ</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">II</mi></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="14pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="4892aa3ac68c36effb219e5c5d9b16f5"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-5605-2021-ie00004.svg" width="14pt" height="16pt" src="acp-21-5605-2021-ie00004.png"/></svg:svg></span></span> is verified based on the result that the deviation between the measured and theoretical values is less than 6 % for the size-resolved spherical polystyrene latex (PSL). The AAC-SPAMS system was applied to characterize the <span class="inline-formula"><i>D</i><sub>ve</sub></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M16" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi mathvariant="italic">ρ</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">II</mi></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="14pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="2b2a12659865b803cc30d80e87964d70"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-5605-2021-ie00005.svg" width="14pt" height="16pt" src="acp-21-5605-2021-ie00005.png"/></svg:svg></span></span> of (NH<span class="inline-formula"><sub>4</sub></span>)<span class="inline-formula"><sub>2</sub></span>SO<span class="inline-formula"><sub>4</sub></span> and NaNO<span class="inline-formula"><sub>3</sub></span> particles, suggesting that these particles are aspherical and their <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M21" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi mathvariant="italic">ρ</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">II</mi></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="14pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="7a8d32bd49762f8790d19ee17b9c3a57"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-5605-2021-ie00006.svg" width="14pt" height="16pt" src="acp-21-5605-2021-ie00006.png"/></svg:svg></span></span> is independent of particle size. Finally, the AAC-SPAMS system was deployed in a field measurement, showing that it is a powerful technique to characterize the chemically resolved <span class="inline-formula"><i>D</i><sub>ve</sub></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M23" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi mathvariant="italic">ρ</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">II</mi></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="14pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="c6c4e04de00b4f177f25ad00955616f5"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-5605-2021-ie00007.svg" width="14pt" height="16pt" src="acp-21-5605-2021-ie00007.png"/></svg:svg></span></span> of particles in real time.</p>