Exceptional Event Analysis Draft, July 13, 2005

Exceptional PM25 Events Exceptional air pollution events are due to sources outside the jurisdiction of control agencies (??) Exceptional PM25 events are primarily due to biomass (forest,grass) smoke and windblown dust The composition of smoke is dominated by organic carbon (OCf) as shown in the pie chart Windblown dust is composed of crustal elements, Si, Al, FE, Ca etc. A robust way of identifying smoke events is by the unusually high OC fraction of PM25 mass, such as the Quebec Smoke event, compared to the average.

Event Dates and Locations IMPROVE and STN chemical data available for 2003 Events are analyzed using three station configurations: –STN site , Chattanooga –IMPROVE site COHU1 –Aggregate of 14 IMP&STN sites COHU IMP & STN 14 site avg

Chemical Pattern at Chattanooga STN In 2003, at Chattanooga STN site, the chemical data are available for four ‘event’ days The four days represent high PM2.5 concentrations (>40 ug/m3) at the Chattanooga site The time series for total organics shows that the ‘event’ days are among the highest for the period On the same event days, the fine particle sulfate concentration is also high except on April 15, 2003 The organic fraction of PM2.5 during the event days was below 20% except on April 15, 2003 OC/PM25 PM25 SO4 OC

IMPROVE COHU1 OC/PM25SO4 OCPM25 The closest IMPROVE site to Chattanooga is at Cohu which has six “event days” in The six days represent high PM2.5 concentrations (~30 ug/m3) at the Cohu site The time series for total organics shows that the ‘event’ days are among the highest for the period On the same event days, the fine particle sulfate concentration is also high (~15 ug/m3) The organic fraction of PM2.5 during the event days was below 20%

IMPROVE & STN 14 Sites OC/PM25SO4 OCPM25 The regional aerosol chemistry pattern is examined by aggregating 14 IMPROVE/STN sites. The seven event days in 2003 have high PM2.5 concentrations (20-40 ug/m3) The total organics data show moderate to high regional OC levels (5-10ug/m3) during the ‘event’ days On the same event days, sulfate concentration is also high (8-16ug/m3) The organic fraction of PM2.5 during the event days was about 20% except on April 15, 2003 (~30%) Thus, it is evident, that the regional OC is relatively low,

Individual Event Analyses Individual Event Analyses (only seven days so far) There will be a set pattern for the individual exceptional day analysis, e.g. the list of images and discussion at the left for April 15, 2003 Each image is linked to the viewer for more detailed browsing, comparison etc., as shown below The structured ‘story’ for each exceptional day/event will be added to the images April 15, 2003 The use of the tools is/will be explained through web-based tutorials, e.g. Introduction to DataFed Catalog and browser (Flash presentation with sound) Introduction to DataFed Catalog and browser