Evaluation of a Heated-Inlet for Calibration of the SP2

Abstract

Black carbon (BC) calibration standards, such as fullerene soot, are routinely used to calibrate single-particle soot photometer (SP2) instruments. Impurities in BC standards create uncertainties in these calibrations, and thus it is desirable to remove non-BC compounds from the aerosol, though removal processes must not significantly alter BC microphysical properties. We present a series of experiments using mobility- and mass-selected fullerene soot particles to assess the performance of a high-temperature denuder system for treating BC prior to SP2 analysis. Particle mass, incandescence, and scattering properties were measured by tandem aerosol particle mass analyzers and an SP2, after thermal treatment at a range of temperatures and residence times (RT). For a longer RT (e.g., ∼6 s at 300°C), monodisperse fullerene soot particles of initial mass 1.4 fg decreased in mass with increasing temperature, by 3% at 300°C to 15% at 600°C. Mass losses were similar for fullerene soot particles of initial mass 10.7 fg. The peak height of the particle laser-induced incandescence (LII) and scattering intensities of the 10.7 fg fullerene soot increased by 7% and 3%, respectively, at 300°C, and by over 15% and 10% at 400°C, possibly due to microphysical changes after heating. When sampling through a 300°C denuder with a particle RT of 2.5 s, the LII intensity of ambient BC particles of initial mass 1.1 fg increased by 8%. In light of these results, denuder temperatures of ∼300°C with 0.4 s ≤ RT ≤ 2.5 s are recommended for SP2 calibration. Copyright 2013 American Association for Aerosol Research