Development of a portable laser-flash photolysis Faraday rotation spectrometer for measuring atmospheric total OH reactivity
<p>Quantitative measurements of atmospheric total OH reactivity (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow><msu...
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| Main Authors: | , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-03-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://amt.copernicus.org/articles/18/1243/2025/amt-18-1243-2025.pdf |
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| Summary: | <p>Quantitative measurements of atmospheric total OH reactivity (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi>k</mi><mrow class="chem"><mi mathvariant="normal">OH</mi></mrow><mo>′</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="20pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="3849a30c9dc911b94a681f63125e5695"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-18-1243-2025-ie00001.svg" width="20pt" height="15pt" src="amt-18-1243-2025-ie00001.png"/></svg:svg></span></span>) provide crucial insights into atmospheric photochemistry. However, widespread application of total OH reactivity measurements is challenging due to insufficient equipment and the complexity of existing instrumentation. In this work, we report the development of a portable laser-flash photolysis Faraday rotation spectroscopy (LP-FRS) instrument for real-time and in situ measurement of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M2" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi>k</mi><mrow class="chem"><mi mathvariant="normal">OH</mi></mrow><mo>′</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="20pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="552e0d3a2315ba1d60d16278bb83421d"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-18-1243-2025-ie00002.svg" width="20pt" height="15pt" src="amt-18-1243-2025-ie00002.png"/></svg:svg></span></span>. To achieve efficient overlapping between the pump and probe laser and realize a long effective absorption path length, thus enabling high-sensitivity measurement, a specific Herriott-type pump–probe optical multi-pass cell was designed. The instrument's optical box dimensions were 130 <span class="inline-formula">cm</span> <span class="inline-formula">×</span> 40 <span class="inline-formula">cm</span> <span class="inline-formula">×</span> 35 <span class="inline-formula">cm</span>. The obtained effective absorption path was <span class="inline-formula">∼</span> 28.5 <span class="inline-formula">m</span> in a base length of 77.2 <span class="inline-formula">cm</span>. The <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M11" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi>k</mi><mrow class="chem"><mi mathvariant="normal">OH</mi></mrow><mo>′</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="20pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="1e833a76ffad29bbe2689e71e449b546"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-18-1243-2025-ie00003.svg" width="20pt" height="15pt" src="amt-18-1243-2025-ie00003.png"/></svg:svg></span></span> detection precisions of the LP-FRS instrument were 2.3 and 1.0 <span class="inline-formula">s<sup>−1</sup></span> with averaging times of 60 and 300 <span class="inline-formula">s</span>, respectively. The <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M14" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi>k</mi><mrow class="chem"><mi mathvariant="normal">OH</mi></mrow><mo>′</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="20pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="a7c6690b6bac039d666646c5b5e9ae58"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-18-1243-2025-ie00004.svg" width="20pt" height="15pt" src="amt-18-1243-2025-ie00004.png"/></svg:svg></span></span> measurement uncertainty was evaluated to be within 2 <span class="inline-formula">s<sup>−1</sup></span>. Field measurement was performed, and the difference between the measured <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M16" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi>k</mi><mrow class="chem"><mi mathvariant="normal">OH</mi></mrow><mo>′</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="20pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="781901bd9c68959a83d524b46f5cae82"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-18-1243-2025-ie00005.svg" width="20pt" height="15pt" src="amt-18-1243-2025-ie00005.png"/></svg:svg></span></span> and the model simulated from the measured reactive species was analysed. The developed portable LP-FRS instrument extends the measurement methods of atmospheric total OH reactivity and has certain advantages in terms of cost, operation, and transportation, which will play an increasingly important role in future atmospheric chemistry research.</p> |
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| ISSN: | 1867-1381 1867-8548 |