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Worst 20% Hazes Across the Country. Based on IMPROVE Speciation Data by Marc Pitchford August 2001. What Causes Worst Day & When do the Occur. Southeastern US Sulfate dominates worst case days Most worst case days are in the late summer, rare to have any during cold periods
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Worst 20% Hazes Across the Country Based on IMPROVE Speciation Data by Marc Pitchford August 2001
What Causes Worst Day & When do the Occur • Southeastern US • Sulfate dominates worst case days • Most worst case days are in the late summer, rare to have any during cold periods • Northeastern US • Sulfates dominate with occasional high nitrate • Many worst days are in the summer, but every season has some worst days
What Causes Worst Day & When do the Occur • Northern Tier • Sulfates contribute any time of year • Nitrates contribute primarily in the Winter • Organics are occasionally important in the Summer
What Causes Worst Day & When do the Occur • Interior Western US • Sulfates, Organics, & Coarse Mass share the blame on most worst case days • Apparent fire emissions (very high organic & elemental carbon) are sporadically responsible for unusually high haze levels • Apparent dust storms (very high coarse mass & fine soil) are occasionally responsible for unusually high haze levels
What Causes Worst Day & When do the Occur • California • Nitrate, sulfate, & organic species contribute most on worst days • Worst days are distributed throughout the year
What Causes Worst Day & When do the Occur • Alaska • Sulfate is important especially in the cold seasons (arctic haze from Eurasia?) • Organic is important especially in the warm seasons (apparently from forest fires)