BRET1 (Breton NWR, LA, Lat. 29.1189, Long. -89.2066, Alt. 11)
IMPROVE sampling started on 8/22/2000 at Breton NWR. Only 9 sampling days have data available in 2000. Although not as many as in 2000, there are still lots of days without any concentration data available during 2001 - 2004. Based on the regional haze rule version 2, zero year of complete aerosol data is available in Breton during the baseline period of 2000-2004. Table 1 lists the number of valid sampling days in each month during 2001-2004.
Table 1. Number of measurements available in each month during 2001-2004
Location | Month | 2000 | 2001 | 2002 | 2003 | 2004 | Total |
---|---|---|---|---|---|---|---|
BRET1 | 1 | 1 | 9 | 9 | 10 | 29 | |
BRET1 | 2 | 3 | 10 | 9 | 9 | 31 | |
BRET1 | 3 | 7 | 10 | 11 | 11 | 39 | |
BRET1 | 4 | 6 | 5 | 10 | 10 | 31 | |
BRET1 | 5 | 7 | 3 | 10 | 6 | 26 | |
BRET1 | 6 | 9 | 2 | 10 | 9 | 30 | |
BRET1 | 7 | 10 | 3 | 10 | 9 | 32 | |
BRET1 | 8 | 10 | 10 | 11 | 11 | 42 | |
BRET1 | 9 | 10 | 8 | 2 | 2 | 22 | |
BRET1 | 10 | 8 | 10 | 18 | |||
BRET1 | 11 | 10 | 10 | 4 | 24 | ||
BRET1 | 12 | 10 | 11 | 10 | 31 |
The discussion below is based on all the valid measurements during 2001-2004 in Breton NWR. As shown in Figure 1, the overall average total light extinction coefficient (Bext) at Breton NWR is 77.8 Mm-1 (Visual Range ~ 62 Km; Deciview ~ 20). The average PM2.5 mass concentration is 8.2 mg/m3. The average contributions of the major aerosol components to Breton haze are particulate sulfate 58.1%, nitrate 7.7%, organic matter (OMC) 7.9%, elemental carbon (light absorbing carbon, LAC) 4.0%, fine soil 1.0%, sea salt 1.8%, and coarse mass (CM) 5.3%.
Figure 3 Average contributions of major aerosol chemical components to light extinction (Based on data available in 2001-2004)
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)
As Figure 2 indicates, the average light extinction coefficient during the 20% worst days is 137.8 Mm-1, which is about 3.4 times of the value of 40.9 Mm-1 during the 20% best days and 2.0 times of the value of 69.1 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 ~ 68%.
Figure 3 suggests that the highest occurrence of the 20% worst days happened in September, in which ~ 50% of the sampling days are the 20% haziest days at Breton. As shown in Figure 6, in the 20% worst visibility days, sulfate is the largest aerosol contributor to haze with a contribution from ~50% in the winter to ~80% in the summer. Nitrate and OMC each contributes about 10-20% to light extinction in the 20% worst days during the winter and early spring.
Figure 5 Percentage of sampling days that are 20% worst days in each month (Based on data available in 2001-2004)
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)