AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Calibrating Black Carbon Mass Measurement Instruments Using the CPMA-electrometer System
MATTHEW DICKAU, Tyler Johnson, Kevin Thomson, Gregory Smallwood, Jason S. Olfert, University of Alberta
Abstract Number: 647 Working Group: Instrumentation and Methods
Abstract Previously, it has been shown that a centrifugal particle mass analyzer (CPMA, Cambustion) can be used in conjunction with an aerosol electrometer to measure the mass concentration of a charged aerosol in real time (Symonds et al 2013). The CPMA selects the aerosol by mass-to-charge ratio and the electrometer measures the charge concentration. This system can be used to rapidly calibrate less traceable mass measurement instruments.
Soot from an inverted burner, with a median mobility diameter of 270 nm, was passed through a denuder to eliminate organic carbon (verified by EC/OC analysis), and then through a unipolar diffusion aerosol charger (UDAC, Cambustion) before passing through the CPMA. Downstream of the CPMA, the flow was split between the electrometer and the challenge instrument. The mass concentration was varied from around 5 µg/m$^3 to 150 µg/m$^3 by manipulating the CPMA setpoint. This experiment compared the results of the CPMA-electrometer system with those of two laser-induced incandescence instruments (LII 300, Artium Technologies) and two Micro-Soot Sensor photoacoustic instruments (MSS, AVL). The challenge instruments had been previously calibrated to the NIOSH 5040 standard, which has a stated uncertainty of 16% at concentrations of 23 µg/m$^3.
The correlations between the CPMA-electrometer system and the challenge instrument were highly linear for both the LII and the MSS, and agreed well with the previous calibration. The LII models both had a slope of 0.956, and had R$^2 values of 0.999 and 0.996. The MSS models had slopes of 1.05 and 1.09, both with R$^2 values of 0.999. The uncertainty in the CPMA-electrometer system averaged 7% and was as low as 3% for some measurements. The lower uncertainty and speed of measurement support the use of the CPMA-electrometer system as a mass measurement calibration method for nanoparticulate black carbon.
References:
Symonds, J., Reavell, K., & Olfert, J. (2013). The CPMA-Electrometer System - A Suspended Particle Mass Concentration Standard. Aerosol Science and Technology, Vol. 47, Iss. 8.