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Measurement of black carbon (BC) by an optical method and a thermal-optical method: Intercomparison for four sites

2009-12-01
Tanveer, Ahmed
Vincent Ahmed, Dutkiewicz
Akhtar, Shareef
Tuncel, Süleyman Gürdal
TUNCEL, SEMRA
Liaquat, Husain
Comparison of black carbon (BC) measurements obtained by two methods was performed for aerosols samples collected on Whatman 41 (W-41) filters, using an optical method (Magee Scientific Optical Transmissometer Model OT-21) and a thermal-optical method (Sunset Laboratory Thermal-optical analyzer). Samples were collected from four sites: Albany (a small urban site, NY), Antalya (coastal site, Turkey), Whiteface Mountain (remote site, NY) and Mayville (rural site, NY). At Albany, comparison between the two methods showed excellent agreement; a least-squares regression line yielded a slope of 1.02, and r(2) = 0.88. Similar comparisons at Antalya (slope of 1.02, r(2) = 0.5) and Whiteface Mountain (slope of 0.92 and r(2) = 0.58) also gave very good relationship. At Mayville, the relationship between the two methods yielded somewhat lower regression: a slope of 0.75, and r(2) = 0.44. The data from the four locations, when plotted together, yielded an excellent agreement: a slope of 0.91, and r(2) of 0.84. Based on our measurements, it appears that optical measurement using the OT-21 can be successfully applied to determination of BC in W-41 filters. However, because of the variability in the chemical composition of BC aerosol at different locations, it is suggested that the calibration of OT-21 when using W-41 filters should be performed with a statistically significant numbers of samples for specific sites.