MING1 (Mingo NWR, MO, Lat. 36.9717, Long. -90.1432, Alt. 111.3) Print-Friendly Version Print-Friendly Version (B&W)
IMPROVE sampling started on 6/3/2000 at Mingo NWR. Therefore, no complete aerosol data is available in 2000. From 6/1/2002 to the end of 2004, OC/EC concentrations are missing due to possible problems with the channel C sampler, although concentrations of the other major components are available most of the time during this period. Based on the regional haze rule version 2, only 1 year (2001) of complete aerosol data are available in Mingo during the baseline period of 2000-2004. The "Guidance for tracking progress under the regional haze rule" states that "if maximum data recovery is not achieved, EPA believes that a minimum of 3 years of data meeting these completeness requirements is sufficient to calculate the 5-year averages within each 5-year period. This recommendation for at least 3 years out of 5 is consistent with the policy established in EPA’s regulations governing monitoring and analysis of PM2.5, which establishes minimum data requirements for PM2.5 NAAQS comparisons". Because only OC/EC concentrations are missing from 6/1/2002 to the end of 2004, we tried to estimate the missing OC/EC concentrations using the measured concentrations of other components such as hydrogen (H) and Sulfur (S). Based on the data in 2001, a nice correlation has been found between the so-called organic hydrogen (H-1/4*S) and measured OC as shown in Figure 1. Therefore, the missing OC concentrations in 2004 may be estimated as 8.0 times organic H concentrations based on measured H and S concentrations during these days (OC is set to be zero if the calculated organic H is negative). Figure 2 suggests that the EC to OC ratio is about 0.2 during 2001. So, the missing EC concentrations in 2004 can be estimated as 0.2 times calculated OC concentrations.
Figure 1 Relationship between organic H and measured OC in 2001
Figure 2 Relationship between measured OC and EC in 2001
After substituting the missing OC/EC data in 2002-2004 using the methodology described above, 4 years of complete aerosol data (2001-2004) are available in Mingo NWR during the baseline period of 2000 - 2004. As shown in Figure 3, the overall average total light extinction coefficient (Bext) at Mingo NWR is 92.8 Mm-1 (Visual Range ~ 54 Km; Deciview ~ 21). The average PM2.5 mass concentration is 11.0 mg/m3. The average contributions of the major aerosol components to Mingo haze are particulate sulfate 47.8%, nitrate 15.7%, organic matter (OMC) 13.3%, elemental carbon (light absorbing carbon, LAC) 4.2%, fine soil 0.9%, sea salt 0.3%, and coarse mass (CM) 4.9%.
Figure 3 Average contributions of major aerosol chemical components to light extinction (Based on data available in 2001-2004) (B&W)
Figure 4 Average contributions of major aerosol chemical components to light extinction in 20% best, middle 60% and 20% worst days (Based on data available in 2001-2004) (Data Table) (B&W)
As Figure 4 indicates, the average light extinction coefficient during the 20% worst days is 170.3 Mm-1, which is about 4.1 times of the value of 41.2 Mm-1 during the 20% best days and 2.0 times of the value of 83.2 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 ~ 57%. Nitrate and OMC contribute about 16% and 12%, respectively, to light extinction during the 20% worst visibility days.
Figure 5 suggests that the highest occurrence of the 20% worst days happened in September, in which ~ 42% of the sampling days are the 20% haziest days at Mingo. As shown in Figure 6, in the 20% worst visibility days, sulfate is the largest aerosol contributor to haze (from ~30% in November to ~80% in July) except in January and December when nitrate dominates the aerosol light extinction with a contribution of ~50%. Nitrate also contributes about 25-35% during the 20% worst days in February and March, and OMC contributes about 20-30% during the 20% worst days in October and November.
Figure 5 Percentage of sampling days that are 20% worst days in each month (Based on data available in 2001-2004) (Data Table) (B&W)
Figure 6 Average contributions of major aerosol chemical components to light extinction during 20% worst days in each month (Based on data available in 2001-2004) (Data Table) (B&W)
List of Tables:
1. Number of measurements available in each month during 2001-2004
4. Percentage of worst days happened in each month based on data available during 2001-2004
