ROMA1 (Cape Romain NWR, SC, Lat. 32.941, Long. -79.6572, Alt. 4.7)      

Based on the regional haze rule version 2, 5 years of complete aerosol data are available in Cape Romain NWR during the baseline period of 2000 - 2004. As shown in Figure 1, the overall average total light extinction coefficient (Bext) is 84.5 Mm-1 (Visual Range ~  59 Km; Deciview ~ 20). The average PM2.5 mass concentration is 9.0 mg/m3. The average contributions of the major aerosol components to Cape Romain haze are particulate sulfate 55.2%, nitrate 5.7%, organic matter (OMC) 14.5%, elemental carbon (light absorbing carbon, LAC) 4.6%, fine soil 0.6%, sea salt 1.5%, and coarse mass (CM) 3.8%. 

Bext = 84.5 Mm-1

Figure 1 Average contributions of major aerosol chemical components to light extinction (Based on data available in 2000-2004)

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 2000-2004)

As Figure 2 indicates, the average light extinction coefficient during the 20% worst days is 147.3 Mm-1, which is about 3.5 times of the value of 42.4 Mm-1 during the 20% best days and 1.9 times of the value of 76.9 Mm-1 during the middle 60% days. Sulfate is the largest aerosol contributor to light extinction during the 20% worst days, with a contribution of  ~ 66%. OMC also contributes about 16% to light extinction during the 20% worst visibility days.

Figure 3 suggests that the highest occurrence of the 20% worst days happened in July, in which ~ 45% of the sampling days are the 20% haziest days at Cape Romain. As shown in Figure 4, in the 20% worst visibility days, sulfate is the largest aerosol contributor to haze throughout the year, with a contribution from ~ 40% in the first quarter to ~ 75% in the third quarter. OMC also contributes ~23-36% during the 20% worst days in the winter and spring (January to April, November to December).

Figure 3 Percentage of sampling days that are 20% worst days in each month (Based on data available in 2000-2004)

 

Figure 4 Average contributions of major aerosol chemical components to light extinction during 20% worst days in each month (Based on data available in 2000-2004)