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Event Evidence Analysis
During the July 6-18 event period, chemical data are available for July 7, 10,16, and 18. On July 7 the SmokeBioMass concentration show extreme levels covering New England and Virginia, clearly attributable to the Quebec fire event. Moderate SmokeBioMass concentrations are observed throughout the southeast including SC. In comparison, the sulfate concentration is also high throughout the southeastern U.S. as well as through much of the Midwest. These high sulfate levels arose from stagnation that occurred prior to July 6.
On July 7, the SmokeBioMass concentration at Greenville, SC was 12.6 mg/m3, which is 47% of the PM2.5 mass concentration. This fraction is higher than the long-term average of 45% at Greenville. Thus, on July 7, at Greenville the above average SmokeBioMass is an indication of smoke impact on PM2.5 mass.
Fire and Transport:
The source region of the Quebec smoke is well documented through fire pixels and satellite detected smoke. The transport pattern toward New England is best documented through the satellite images. From the daily satellite data it is evident that the Quebec smoke did not reach South Carolina, but drifted southeastward to the Atlantic. On July 7, sources of smoke are evident from the numerous satellite pixels. The largest density of fire pixels is in northern Quebec caused by the well documented boreal forest fires. Less dense fire pixels are also visible in the S.E. US over the LA/GA corridor. The five day back trajectory to Greenville, SC (July 7) indicates air mass transport from the northwestern U.S. and passage over the Great Lakes. Over that transport path there is no evidence of fire pixels. In fact, the same transport path is evident for four days, July 6-9 period of the Quebec smoke event.
On July 7, the surface winds over the NE were from northeast direction clearly indicating the direction of the Quebec smoke transport in the surface layer. The same transport path is followed by the upper air ATAD trajectories. On the other hand, the SE U.S. was under a stagnating air mass for much of early July, which was conducive for the accumulation of local emissions. Thus, from the point of view of smoke sources and transport there is no evidence that the Quebec smoke has impacted S.C.
On July 7, 2002 the daily average PM2.5 contours from the EPA FRM and IMPROVE samplers indicate two regions of elevated PM2.5: the extreme high smoke region in the northeastern U.S. and another in the southeastern U.S. and the Gulf of Mexico. The SeaWiFS satellite AOT also shows the separate northeastern (Quebec smoke) and southeastern "haze blob" as separate entities. Hence, the southeastern haze is of different origin than the Quebec smoke.
The time series of PM2.5 at Greenville, SC indicate 20-25 mg/m3 throughout the July 6-18, 2002 period.
During July 6-9, 2002 the Quebec smoke event has produced record PM2.5 concentrations throughout the Northeast and Southeastern Canada . The moderate PM2.5 (20-25 mg/m3) concentration at Greenville, SC was influenced by a major stagnating episode that accumulated sulfate in the southeastern US since July 4, 2002. In addition, the stagnation resulted in the accumulation of SmokeBioMass from local sources, within South Carolina and neighboring states in the Southeast. There is no evidence that would point to the Quebec Smoke as a significant contributor to the episode in any part of South Carolina..