Comparison between two different nanoparticle size spectrometers

Abstract

A commercial differential mobility particle sizer (DMPS), long and medium column DMA (Grimm Aerosol Technik L-DMA model 5.400; M-DMA model 5500), condensation particle counter (CPC, Grimm Aerosol Technik 5.403), and a fast mobility particle sizer (FMPS-TSI, model 3091), were deployed to determine the size distributions of ultrafine particles. Comparisons were performed using atmospheric aerosol, as well as laboratory aerosol generated by nebulizing Milli-Q water (Millipore Corporation) and a water suspension of Fe2O3 in a Collison type atomizer. Results show that the DMPS generally measured higher particle number concentrations than the FMPS, above all for atmospheric aerosol compared to laboratory generated aerosol. With regard to size distribution, in both the atmospheric and laboratory-generated aerosols, the FMPS always showed a small peak around 10 nm, which was not shown by the M-DMPS. The agreement of the particle number concentration between the DMPS and FMPS was better in the 25-116 nm range for atmospheric aerosol, and in the 10-65 nm range for laboratory-generated aerosols. Since these instruments are scheduled to be run for air quality measurements and not only aerosol research purposes, there is an urgent need to establish working protocols in compliance with requirements with ISO 15900 requirements.

Implications: Epidemiological studies have shown that high ultrafine particulate concentrations are associated with an increase in mortality. Measuring exposure against mass alone is not sufficient, but it is also necessary to consider exposure against number concentration. Therefore, continuous measurements of aerosol size and number concentrations are important. This paper provides a comparison between two different nanoparticle size spectrometers widely used in air quality measurements. We found significantly different total number particle concentrations and size distributions in both laboratory-generated and atmospheric aerosols. Results show that the DMPS generally measured higher particle number concentrations than the FMPS. Since these instruments are scheduled to be run for air quality measurements and not only aerosol research purposes, there is an urgent need to establish working protocols in compliance with ISO 15900 requirements.