Portable calibrator for NO based on the photolysis of N₂O and a combined NO₂∕NO∕O₃ source for field calibrations of air pollution monitors

• Main Authors: J. W. Birks, A. A. Turnipseed, P. C. Andersen, C. J. Williford, S. Strunk, B. Carpenter, C. A. Ennis
• Format: Article
• Language: English
• Published: Copernicus Publications 2020-03-01
• Series: Atmospheric Measurement Techniques
• Online Access: https://www.atmos-meas-tech.net/13/1001/2020/amt-13-1001-2020.pdf

<p>A highly portable calibration source of nitric oxide (NO) based on the photolysis of nitrous oxide (<span class="inline-formula">N₂O</span>) supplied by 8 or 16&thinsp;g disposable cartridges is demonstrated to serve as an accurate and reliable transfer standard for the calibration of NO monitors in the field. The instrument provides output mixing ratios in the range 0–1000&thinsp;ppb with a precision and accuracy better than the greater of 3&thinsp;ppb or 3&thinsp;% of the target NO mixing ratio over a wide range of environmental conditions of ambient temperature (8.5–35.0&thinsp;<span class="inline-formula">^∘</span>C), pressure (745–1015&thinsp;mbar corresponding to 2.7–0.0&thinsp;km of elevation), and relative humidity (0&thinsp;%–100&thinsp;%&thinsp;RH). The combination of the NO calibration source with a previously described ozone calibration source based on the photolysis of oxygen in air provides a new instrument capable of outputting calibrated mixing ratios of NO, ozone (<span class="inline-formula">O₃</span>), and nitrogen dioxide (<span class="inline-formula">NO₂</span>), where the <span class="inline-formula">NO₂</span> is produced by the stoichiometric gas-phase reaction of NO with <span class="inline-formula">O₃</span>. The portable <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M9" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msub><mi mathvariant="normal">NO</mi><mn mathvariant="normal">2</mn></msub><mo>/</mo><mi mathvariant="normal">NO</mi><mo>/</mo><msub><mi mathvariant="normal">O</mi><mn mathvariant="normal">3</mn></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="65pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="1de30a4787f90cc6b8f7a18095c3f554"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-13-1001-2020-ie00003.svg" width="65pt" height="14pt" src="amt-13-1001-2020-ie00003.png"/></svg:svg></span></span> calibration source requires no external gas cylinders and can be used for calibrations of NO, <span class="inline-formula">NO₂</span>, and <span class="inline-formula">O₃</span> instruments for mixing ratios up to 1000, 500, and 1000&thinsp;ppb, respectively. This portable calibrator may serve as a convenient transfer standard for field calibrations of ozone and <span class="inline-formula">NO_<i>x</i></span> air pollution monitors.</p>