Evaluation of ogawa passive sampling devices as an alternative measurement method for the nitrogen dioxide annual standard in El Paso, Texas

Nitrogen Dioxide (NO2) is a common urban air pollutant that results from the combustion of fossil fuels. It causes serious human health effects, is a precursor to the formation of ground level ozone, another serious air pollutant, and is one of the six criteria air pollutants established by the United States (U.S.) Clean Air Act (CAA). Ogawa Passive Sampling Devices (PSDs) for NO2 were collocated and operated at six NO2 Federal Reference Method (FRM) monitor locations in the El Paso, Texas area for the 2004 calendar year. Passive samples were taken at 2-week, 3-week, and 4-week intervals and compared against the continuously operating FRM monitors. Results showed that the collective NO2 annual arithmetic mean for all passive monitors was identical to the NO2 mean for all FRM monitors. Of the individual locations, three passive annual NO2 means were identical to their corresponding FRM means, and three passive annual NO2 means differed from their corresponding FRM means by only one part per billion (ppb). Linear correlation analysis between all readings of the individual NO2 PSDs and FRM values showed an average absolute difference of 1.2 ppb with an r2 of 0.95. Paired comparison between high and low concentration annual NO2 sites, seasonal considerations, and interlab quality control comparisons all showed excellent results. The ease of deployment, reliability, and the cost-savings that can be realized with NO2 PSDs could make them an attractive alternative to FRM monitors for screening purposes, and even possibly an equivalent method for annual NO2 monitoring. More tests of the Ogawa NO2 PSD are recommended for different ecosystem and climate regimes.