Loading Effect Correction for Real-Time Aethalometer Measurements of Fresh Diesel Soot

In this study, a correction was developed for the aethalometer to measure real-time black carbon (BC) concentrations in an environment dominated by fresh diesel soot. The relationship between the actual mass-specific absorption co-efficient for BC and the BC-dependent attenuation coefficients was determined from experiments conducted in a diesel exposure chamber that provided constant concentrations of fine particulate matter (PM; PM_2.5; PM <2.5 μm aerodynamic diameter) from diesel exhaust. The aethalometer reported BC concentrations decreasing with time from 48.1 to 31.5 μg m^-3 when exposed to constant PM_2.5 concentrations of 55 ± 1 μg m^-3 and b_scat 95 ± 3Mm^-1 from diesel exhaust. This apparent decrease in reported light-absorbing PM concentration was used to derive a correction K (ATN) for loading of strong light-absorbing particles onto or into the aethalometer filter tape, which was a function of attenuation of light at 880 nm by the embedded particles.