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| Spokane |
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| Chemical components
responsible for haze |
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|
The average PM2.5 mass
concentration during the years 1997-2002 is 7.0 µg/m3, and the average total
light extinction coefficient (Bext) is 48.9 Mm-1 (Visual Range ~ 80 Km; Deciview ~ 15.9). As illustrated in Figure 2, the average
contributions of the major aerosol components to the Spokane haze
are particulate sulfate 16.9%, nitrate 12.5%, organic matter (OMC) 28.6%,
elemental carbon (light absorbing carbon, LAC) 7.2%, fine soil 4.1% and
coarse mass (CM) 10.2%. |
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| Figure 2. Average
contributions of major aerosol chemical components to light extinction
(Based on data available in 1997-2002) |
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Figure 3 suggests that the
highest occurrence of the 20% worst days happened in November and December
during which approximately 50 to 60% of the sampling days are the 20%
haziest days at the Spokane site. |
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 |
| Figure 3. Percentage of
sampling days that are 20% worst days in each month (Based on data available
in 1997-2002) |
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| As shown in Figure 4, OMC is
the largest aerosol contributor to haze during the 20% worst days the whole
year except February and May. Nitrate and CM are the largest aerosol
contributors to haze in the 20% worst days in February and May,
respectively. |
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 |
| Figure 4. Average
contributions of major aerosol chemical components to light extinction
during 20% worst days in each month (Based on data available in 1997-2002) |
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| For a detailed examination of
the aerosol characteristics at Spokane site consult the
aerosol description web page. |
