2002 Annual

Tuesday, 15 January 2002: 4:00 PM
Interpretation of NOy, O3, and CO Data from Northeast Oxidant and Particle Study
J. William Munger, Harvard University, Division of Engineering and Applied Sciences, Cambridge, MA; and B. G. Doddridge and R. D. Clark
Poster PDF (178.0 kB)
As part of the Northeast oxidant and particle study (NE-OPS) field campaign in the summers of 1999 and 2001, NO/NOy, CO, and O3 were measured in the surface layer at the Baxter field site in Northeast Philadelphia. These data will be compared to a climatology of aged air pollutants in a rural setting developed from similar measurements made at the Harvard Forest site in central Massachusetts since 1990.

We address three major questions using this subset of the NE-OPS data. The covariance of NOy and CO in ambient air yields an estimate of the primary emission ratios for urban pollution sources, and provides a test of emission inventories. Apparent depletion of NOy relative to CO provides a measure of pollutant aging. Background ozone levels can be estimated by selecting data with the lowest levels of primary pollutants NOy and CO. By background, we mean the concentration of O3 in air not significantly impacted by recent addition of pollutants.

We infer an emission ratio of 0.18 molecule NOy per molecule of CO in the Philadelphia source region. Periods of intense NOy removal are evident in the data. These periods indicate significant contribution from aged pollutants or very rapid processing of local emissions. An episode of maximum NOy loss stands out as a period having the highest O3 concentrations (30-min. average O3 up to 150 ppb).. The O3 concentration during mid-day periods with the lowest 10% of CO or NOy concentrations is 47 ppb at the Baxter site. The corresponding value for Harvard Forest is 41 ppb.

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