Demonstration of the CPMA-Electrometer System for Calibrating Black Carbon Particulate Mass Instruments

Closure between particulate matter concentrations measured ex situ by thermal–optical analysis and in situ by the CPMA–electrometer reference mass system

“…The CPMA was operated at a mass resolution of 2.5 (the inverse of the normalized fullwidth half maximum) for all MISG-and NRC-IFB measurements, and 2 or 3 for the miniCAST burner. These resolutions are slightly lower than typical operation for the CPMA used in a CERMS (typically >4; Dickau et al 2015) but were adequate. (Note that a mass resolution of 3 would correspond to a size resolution of 9 if our experiment had involved classifying spheres.)…”

“…Also, as the CPMA does not actively remove uncharged particles from its sample flow, the absence of any uncharged particles must be verified experimentally for the above equation to hold (Symonds, Reavell, and Olfert 2013). M classified is generated and measured in the CERMS from traceable quantities (Dickau et al 2015). Unlike TOA, no chemical transformation of the sample is required by CERMS, so the PM mass reported by CERMS is not dependent on sample composition.…”

“…A custom-built inverted flame soot generator (Coderre et al 2011) was designed at the National Research Council (NRC) Canada based on that reported by Stipe et al (2005) and is referred to here as the NRC inverted flame burner (NRC-IFB). The NRC-IFB was operated with methane and air flows of 1.210 and 18.5 standard liters per minute (SLPM, defined at 101.325 kPa and 273 K), respectively, a setpoint with a global equivalence ratio within the range previously determined (Dickau et al 2015) to produce soot particles with a high EC/TC. For one test point, the NRC-IFB soot was diluted with a Dekati ejector dilutor (DI-1000) with preheated and preconditioned dilution air from an in-house compressed-air supply.…”

“…These techniques may be calibrated optically in some cases, but in practice may also be calibrated against an external mass standard. For example, the rBC signals reported by the Artium LII 300 instrument (Artium Technologies Inc., CA, USA) may be calibrated against the nonvolatile mass concentration of soot particles (Dickau et al 2015). Similarly, the signals measured by the single-particle soot photometer (SP2) are exclusively calibrated against the single-particle mass of thermally denuded soot particles (Laborde, Mertes, et al 2012).…”

“…Using silicone diffusion pump oil, Symonds, Reavell, and Olfert (2013) demonstrated closure between the CERMS and gravimetric mass collected on quartz filters to within 6%. Using an inverted-flame diffusion burner, Dickau et al (2015) demonstrated the CERMS method for the calibration of an LII 300 and an MSS for soot-BC mass over concentrations of 5-120 mg m À3 . Also using an inverted-flame burner, Titosky et al (2019) systematically investigated the experimental uncertainty of CERMS and determined its repeatability and intermediate precision (a component of reproducibility) as 1.1% and 2.1%, respectively.…”