Atmospheric aerosols monitoring by scanning mobility and optical particle sizers in an urban area

Abstract

Particulate matter in urban areas can range in size from a few nanometers to a few micrometers and is closely related to human health. They have a detrimental influence when inhaled and can lead to deposition of toxic particles in the human respiratory system [1]. This is the motivation to measure particulate matter number and concentration more accurately, which implies that it is necessary to combine several measurement instruments including different measurement principles. The optical particle sizer (OPS) [2] uses light scattering to obtain the number of particles and concentrations in the range from 300 to 10000 nm, while scanning mobility particle sizers (SMPS) [3] derive particle number concentrations from measured particle size distributions covering particle number concentration in bin from less than 10 nm to 1000 nm. Furthermore, it is possible to modify the distribution obtained by optical measurements by searching for the optimal value of the refractive index of the particles to obtain the best possible agreement with the size distribution obtained by measuring the electrical mobility. This research shows the findings of a campaign conducted in the winter of 2020, which aimed to collect urban atmospheric aerosols at three specific locations in the city center of Belgrade. This study comprehensively analyses the diurnal and seasonal variations for urban aerosol particles size distributions in the range from less than 10nm to 10000 nm. Pollution episodes reflected in increased particle number concentration are identified. Particle number-size distribution data contour plots were generated and presented as a function of particle number diameter and sampling time for the period of pollution episodes and for the short events of fireworks.