Worst 20% Hazes Across the Country

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Worst 20 Hazes Across the Country

• Based on IMPROVE Speciation Data
• by Marc Pitchford
• August 2001

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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

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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

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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

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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

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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)

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