ZION1 (Zion, UT, Lat. 37.459, Long. -113.2234, Alt. 1545)
2 year and 10 month aerosol data are available in Zion during the sampling period of 1997 - 2002. As shown in Figure 1, the overall average total light extinction coefficient (Bext) is 26.4 Mm-1 (Visual Range ~ 148 Km; Deciview ~ 9.7). The average PM2.5 mass concentration is 3.5 mg/m3. The average contributions of the major aerosol components to Zion haze are particulate sulfate 16.9%, nitrate 10.4%, organic matter (OMC) 13.0%, elemental carbon (light absorbing carbon, LAC) 6.8%, fine soil 3.4% and coarse mass (CM) 11.6%.
Figure 1 Average contributions of major aerosol chemical components to light extinction (Based on data available in 1997-2002)
Figure 2 Average contributions of major aerosol chemical components to light extinction in 20% best, middle 60% and 20% worst days (Based on data available in 1997-2002)
As Figure 2 indicates, the average aerosol light extinction coefficient (Bext – Rayleigh Scattering (10 Mm-1)) during the 20% worst days is 29.5 Mm-1, which is about 3.8 times of the value of 7.7 Mm-1 during the 20% best days and 1.9 times of the value of 15.2 Mm-1 during the middle 60% days. Nitrate is the largest contributor to aerosol light extinction, with a contribution of 26% in the 20% worst days. Sulfate, OMC and CM each contributes about 20% to the aerosol light extinction in the 20% worst days.
Figure 3 suggests that the highest occurrence of the 20% worst days happened in August, in which ~ 33% of the sampling days are the 20% haziest days at Zion. As shown in Figure 4, OMC is the largest aerosol contributor to haze in the 20% worst days in July and August, with a contribution of ~ 26%. Nitrate is the largest aerosol contributor in January, February, November and December, with a contribution of 35 - 45% in the worst days. CM contributes about 20% - 25% to haze from April to September. Sulfate is the largest aerosol contributor in March and October, with a contribution of ~ 25% in the worst days.
Figure 3 Percentage of sampling days that are 20% worst days in each month (Based on data available in 1997-2002)
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)