PEFO1 (Petrified Forest National Park, AZ, Lat. 35.078, Long. -109.7683, Alt. 1767)
6 years aerosol data are available in Petrified Forest National Park during the sampling period of 1997 - 2002. As shown in Figure 1, the overall average total light extinction coefficient (Bext) is 28.2 Mm-1 (Visual Range ~ 139 Km; Deciview ~ 10.4). The average PM2.5 mass concentration is 4.0 mg/m3. The average contributions of the major aerosol components to Petrified Forest National Park haze are particulate sulfate 19.1%, nitrate 4.6%, organic matter (OMC) 19.4%, elemental carbon (light absorbing carbon, LAC) 8.5%, fine soil 3.4% and coarse mass (CM) 9.4%.
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 35.0 Mm-1, which is about 4.0 times of the value of 8.8 Mm-1 during the 20% best days and 2.3 times of the value of 15.5 Mm-1 during the middle 60% days. OMC is the largest contributor to aerosol light extinction during the 20% worst days, and the contribution of OMC to aerosol light extinction is ~ 38% in worst days. Sulfate also contributes about 24% in the worst days.
Figure 3 suggests that the occurrence of the 20% worst days is pretty constant from April to November, in which ~ 20 - 30% of the sampling days are the 20% haziest days at Petrified Forest National Park. As shown in Figure 4, both sulfate and OMC contribute ~ 20 - 30% to haze in the 20% worst days from July to December. CM is the largest haze contributor in March and April. Relatively high CM and fine soil loadings are found in March, which may be due to occasionally happened dust storm events. OC / EC loadings are much higher than usual during the 20% worst days in June, suggesting that specific pollution events such as forest fires may be responsible for the haziest days in June.
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)