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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Volume 10, issue 6 | Copyright
Atmos. Meas. Tech., 10, 2253-2269, 2017
https://doi.org/10.5194/amt-10-2253-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 15 Jun 2017

Research article | 15 Jun 2017

Use of a heated graphite scrubber as a means of reducing interferences in UV-absorbance measurements of atmospheric ozone

Andrew A. Turnipseed, Peter C. Andersen, Craig J. Williford, Christine A. Ennis, and John W. Birks Andrew A. Turnipseed et al.
  • 2B Technologies, Inc., 2100 Central Ave., Boulder, CO 80301, USA

Abstract. A new solid-phase scrubber for use in conventional ozone (O3) photometers was investigated as a means of reducing interferences from other UV-absorbing species and water vapor. It was found that when heated to 100–130°C, a tubular graphite scrubber efficiently removed up to 500ppb ozone and ozone monitors using the heated graphite scrubber were found to be less susceptible to interferences from water vapor, mercury vapor, and aromatic volatile organic compounds (VOCs) compared to conventional metal oxide scrubbers. Ambient measurements from a graphite scrubber-equipped photometer and a co-located Federal equivalent method (FEM) ozone analyzer showed excellent agreement over 38 days of measurements and indicated no loss in the scrubber's ability to remove ozone when operated at 130°C. The use of a heated graphite scrubber was found to reduce the interference from mercury vapor to ≤3% of that obtained using a packed-bed Hopcalite scrubber. For a series of substituted aromatic compounds (ranging in volatility and absorption cross section at 253.7nm), the graphite scrubber was observed to consistently exhibit reduced levels of interference, typically by factors of 2.5 to 20 less than with Hopcalite. Conventional solid-phase scrubbers also exhibited complex VOC adsorption and desorption characteristics that were dependent upon the relative humidity (RH), volatility of the VOC, and the available surface area of the scrubber. This complex behavior involving humidity is avoided by use of a heated graphite scrubber. These results suggest that heated graphite scrubbers could be substituted in most ozone photometers as a means of reducing interferences from other UV-absorbing species found in the atmosphere. This could be particularly important in ozone monitoring for compliance with the United States (U.S.) Clean Air Act or for use in VOC-rich environments such as in smog chambers and monitoring indoor air quality.

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We investigated a new solid-phase scrubber for use in conventional ozone UV-absorption photometers. A heated graphite scrubber efficiently removed ozone and was less susceptible to interference from water vapor, mercury vapor, and aromatic hydrocarbons compared to conventional metal oxide scrubbers. Reducing interferences from these atmospheric species in conventional ozone photometers could lead to more accurate ozone measurements in compliance monitoring or for indoor air quality.
We investigated a new solid-phase scrubber for use in conventional ozone UV-absorption...
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