Using particle effective density to determine SMPS-based aerosol mass concentration: application to airborne carbon and titanium nanoparticles

Abstract

To avoid multiple instruments to be deployed in field measurement campaigns based on airborne nanoparticles characterization, this study aims at investigating the capability of a Scanning Mobility Particle Sizer (SMPS) to provide accurate data relative to the mass concentration. Two series of test nanoaerosols were produced using a spark-discharge generator equipped with carbon or titanium electrodes (modal number diameters between ~ 50 and ~ 170 nm). The mass concentration was monitored by means of a personal AM520 photometer operated in parallel with the SMPS and closed-face cassette sampling for further off-line analysis: gravimetric analysis, and chemical analysis (thermo-optical analysis for carbon, ICP-OES for titanium). For each operating condition, the average number size distribution stemming from the SMPS was converted into mass size distribution accounting for particle effective density and integrated over the whole range of particle diameters to determine the corresponding mass concentration. Results highlight correlations (R2 ~ 0.9) between SMPS-based and chemical analysis or gravimetric mass concentrations below 1 mg/m3, with relative discrepancies lower than ~ 15% and ~ 25%, respectively. The AM520 photometric response remains dependent on particle physical and light scattering properties, which differ with the test dust used for factory calibration.