Simultaneous detection of ozone and nitrogen dioxide by oxygen anion chemical ionization mass spectrometry: a fast-time-response sensor suitable for eddy covariance measurements
<p>We report on the development, characterization, and field deployment of a fast-time-response sensor for measuring ozone (<span class="inline-formula">O<sub>3</sub></span>) and nitrogen dioxide (<span class="inline-formula">NO<sub>2<...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-04-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://www.atmos-meas-tech.net/13/1887/2020/amt-13-1887-2020.pdf |
| Summary: | <p>We report on the development, characterization, and field
deployment of a fast-time-response sensor for measuring ozone (<span class="inline-formula">O<sub>3</sub></span>) and
nitrogen dioxide (<span class="inline-formula">NO<sub>2</sub></span>) concentrations utilizing chemical ionization
time-of-flight mass spectrometry (CI-ToFMS) with oxygen anion
(<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">O</mi><mn mathvariant="normal">2</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="17pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="26d368ad2bb5d49e9b215b03d31563a9"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-13-1887-2020-ie00001.svg" width="17pt" height="16pt" src="amt-13-1887-2020-ie00001.png"/></svg:svg></span></span>) reagent ion chemistry. We
demonstrate that the oxygen anion chemical ionization mass spectrometer
(Ox-CIMS) is highly sensitive to both <span class="inline-formula">O<sub>3</sub></span> (180 counts s<span class="inline-formula"><sup>−1</sup></span> pptv<span class="inline-formula"><sup>−1</sup></span>) and <span class="inline-formula">NO<sub>2</sub></span> (97 counts s<span class="inline-formula"><sup>−1</sup></span> pptv<span class="inline-formula"><sup>−1</sup></span>), corresponding to
detection limits (<span class="inline-formula">3<i>σ</i></span>, 1 s averages) of 13 and 9.9 pptv,
respectively. In both cases, the detection threshold is limited by the
magnitude and variability in the background determination. The short-term
precision (1 s averages) is better than 0.3 % at 10 ppbv <span class="inline-formula">O<sub>3</sub></span> and 4 %
at 10 pptv <span class="inline-formula">NO<sub>2</sub></span>. We demonstrate that the sensitivity of the <span class="inline-formula">O<sub>3</sub></span>
measurement to fluctuations in ambient water vapor and carbon dioxide is
negligible for typical conditions encountered in the troposphere. The
application of the Ox-CIMS to the measurement of <span class="inline-formula">O<sub>3</sub></span> vertical fluxes
over the coastal ocean, via eddy covariance (EC), was tested during the summer of
2018 at Scripps Pier, La Jolla, CA. The observed mean ozone deposition
velocity (<span class="inline-formula"><i>v</i><sub>d</sub></span>(<span class="inline-formula">O<sub>3</sub></span>)) was 0.013 cm s<span class="inline-formula"><sup>−1</sup></span> with a campaign ensemble
limit of detection (LOD) of 0.0027 cm s<span class="inline-formula"><sup>−1</sup></span> at the 95 % confidence
level, from each 27 min sampling period LOD. The campaign mean and 1
standard deviation range of <span class="inline-formula">O<sub>3</sub></span> mixing ratios was <span class="inline-formula">41.2±10.1</span> ppbv. Several fast ozone titration events from local NO emissions were
sampled where unit conversion of <span class="inline-formula">O<sub>3</sub></span> to <span class="inline-formula">NO<sub>2</sub></span> was observed,
highlighting instrument utility as a total odd-oxygen (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M23" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msub><mi mathvariant="normal">O</mi><mi>x</mi></msub><mspace width="0.125em" linebreak="nobreak"/><mo>=</mo><mspace linebreak="nobreak" width="0.125em"/><msub><mi mathvariant="normal">O</mi><mn mathvariant="normal">3</mn></msub><mspace width="0.125em" linebreak="nobreak"/><mo>+</mo><mspace linebreak="nobreak" width="0.125em"/><msub><mi mathvariant="normal">NO</mi><mn mathvariant="normal">2</mn></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="75pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="d5b8caa296edd90f045d885f0525d6c6"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-13-1887-2020-ie00002.svg" width="75pt" height="13pt" src="amt-13-1887-2020-ie00002.png"/></svg:svg></span></span>) sensor. The demonstrated precision, sensitivity, and time
resolution of this instrument highlight its potential for direct
measurements of <span class="inline-formula">O<sub>3</sub></span> ocean–atmosphere and biosphere–atmosphere exchange
from both stationary and mobile sampling platforms.</p> |
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| ISSN: | 1867-1381 1867-8548 |