Density assessment method of chemical components in urban submicron aerosol particles

Abstract

During the analysis of aerosol particle density variation in urban environment it was noticed that a Quadrupole Aerosol Mass Spectrometer (Q-AMS) and a Scanning Mobility Particle Sizer (SMPS) indicated the particle diameter differently. Measurements presented in this paper were conducted in Šiauliai town from 15 March to 27 March 2012. Size distribution and concentration spectra for non-refractory submicron aerosol particles (PM1) of NH₄⁺, NO₃^–, SO₄^2– and organics were obtained by using Q-AMS and SMPS. The organic particles with a diameter of up to 100 nm were selected for the analysis due to the considerable influence of traffic emission on the sampling site. The major formation of particles in the range of up to 100 nm occurs from pollutants of traffic emissions. It was observed that the density of organic aerosol particles in the range up to 100 nm was relatively too high if compared with the density sum of all components in the range above 100 nm (less than 1 g cm^–3). This observation was opposite to the result that was expected. The latter results imply incorrectness for direct interpretation of the data obtained from Q-AMS and SMPS. Therefore, the method for evaluation of particle diameters provided by Q-AMS and SMPS is discussed in this paper.