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Relationship Between Surface Ozone Concentrations and Other Pollutants
(Continued)

Co-occurrence of Ozone and Daily PM2.5

Using 2001 data from the EPA AQS database, the daily co-occurrence PM2.5 and O3 over a 24-h period was characterized. There were 362 sites where PM2.5 and O3 monitors were co-located. As described in the Introduction, a daily co-occurrence of O3 and PM2.5 was subjectively defined as when an hourly average O3 concentration greater than or equal to 0.05 ppm and a PM2.5 24-h concentration equal to or greater than 40 ug/m3 occurred over the same 24-h period. Figure 5 illustrates the daily co-occurrence patterns observed. Using 2001 data from the AQS database, the daily co-occurrence of PM2.5 and O3 was infrequent.

Figure 5. The co-occurrence pattern for ozone and PM2.5 using 2001 data from AQS.

 

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