BRET1 (Breton NWR, LA, Lat. 29.1189, Long. -89.2066, Alt. 11)          Print-Friendly Version         Print-Friendly Version (B&W)

IMPROVE sampling started on 8/28/2000 at Breton NWR. However, only 9 sampling days have data available in 2000. Although not as many as in 2000, there are still many days without 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

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 PM_2.5 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%. 

Bext = 77.8 Mm^-1

Figure 1 Average contributions of major aerosol chemical components to light extinction (Based on data available in 2001-2004)    (B&W)

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 2001-2004)  (Data Table)    (B&W)

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 4, 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 3 Percentage of sampling days that are 20% worst days in each month (Based on data available in 2001-2004)  (Data Table)    (B&W)

Figure 4 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

2. Average light extinction coefficients (1/Mm) and mass concentrations (mg/m³) of the major aerosol chemical components in 20% best, middle 60% and 20% worst days based on data available during 2001-2004

3. Average light extinction coefficients (1/Mm) and percentage contributions to the aerosol light extinction coefficients (without Rayleigh scattering) of the major aerosol chemical components in 20% best, middle 60%, and 20% worst days based on data available during 2001-2004

4. Percentage of worst days happened in each month based on data available during 2001-2004

5. Average light extinction coefficients (1/Mm) of the major aerosol chemical components during the 20% worst days in each month based on data available during 2001-2004

6. Average light extinction coefficients (1/Mm) of the major aerosol chemical components in each month based on all data available during 2001-2004

Back to Previous Page