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Pinal County Air Quality. October 27, 2008 PM 10 Exceptional/Natural Event. October 27, 2008.
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Pinal County Air Quality October 27, 2008 PM10 Exceptional/Natural Event
October 27, 2008 • Winds associated with abnormally tight pressure gradient caused by high pressure and a back door cold front to the east. The tight pressure gradient caused significant areas of blowing dust. The Maximum winds reached 28 mph and three PCAQCD monitors exceeded the 24-hr PM10 NAAQS. PM10 24-hr Site AQS Site# Conc. (ug/m3) • Stanfield 04-021-3008(3) 212.6 • Stanfield 04-021-3008(1) 201.0 • Maricopa 04-021-3010(3) 159.4
Strong high pressure & “back door” cold front Result in a strong pressure gradient
Casa Grande Airport NWS Observations Sustained wind speed/gust & Visibility
10/27/08 “But for” Test • Stanfield (TEOM) had the following 24-hr PM10 concentrations before/after the 10/27/08 exceptional/natural event • 10/26/08 – 86.2 ug/m3 • 10/28/08 – 87.8 ug/m3 • Maricopa (TEOM) had the following 24-hr PM10 concentrations before/after the 10/27/08 exceptional/natural event • 10/26/08 – 84.0 ug/m3 • 10/28/08 – 72.6 ug/m3