JEM Spotlight: Environmental monitoring of airborne nanoparticles

Abstract

The aim of this work was to review the existing instrumental methods to monitor airborne nanoparticles in different types of indoor and outdoor environments in order to detect their presence and to characterise their properties. Firstly the terminology and definitions used in this field are discussed, which is followed by a review of the methods to measure particle physical characteristics including number, concentration, size distribution and surface area. An extensive discussion is provided on the direct methods for particle elemental composition measurements, as well as on indirect methods providing information on particle volatility and solubility, and thus in turn on volatile and semivolatile compounds of which the particle is composed. A brief summary of broader considerations related to nanoparticle monitoring in different environments concludes the paper.

Intercomparison of a portable and two stationary mobility particle sizers for nanoscale aerosol measurements

“…The deviations among both instruments were considered not statistically significant (p-value > 0.05) ( Table 2 and Figure 2). This difference in NanoScan performance for the DEHS aerosols may be caused by the fact that the Cunningham slip correction factor gets an increasingly weak function of particle diameter with increasing particle size and eventually even passes a minimum (Levin et al 2015), and hence the electrical mobility of unipolar diffusion charged particles (as acquired in the NanoScan) also becomes less sensitive in measuring the particle diameter (Morawska et al 2009b) by acquiring a charge level which is nearly proportional to the particle diameter (Jung and Kittelson 2005;Asbach et al 2011). It should be noted that a constant and unexpected peak was detected around 22-27 nm with NanoScan in each experimental run with DEHS particles, and it is also suggested by the SMPS-L data.…”

Charging State of Aerosols during Particle Formation Events in an Urban Environment and Its Implications for Ion-Induced Nucleation

“…The upper size detection limit of the NAIS effectively restricts it to the nanoparticle size range, which has somewhat arbitrarily been defined as smaller than 50 nm (Morawska et al, 2009). Particles in vehicle emissions, particularly soot, have a mode between 50 and 100 nm.…”

Suppression of Cluster Ions during Rapidly Increasing Particle Number Concentration Events in the Environment

“…There is a plausible explanation for these observations. Most of the particles in an NPF event are secondary volatile particles that are in the nanoparticle size range (Morawska et al, 2009) while the particles produced by fireworks and bush burning consist of mostly primary soot that are much larger in size. Airborne measurements of PNC near biomass burning events in the Northern Territory, Australia (Ristovski et al, 2010), showed that the median diameter of smoke particles were about 90 nm when the flight paths were close to the fires.…”

“…In this way, the NAIS can measure positive and negative cluster ions and charged particle concentrations simultaneously as well as neutral clusters and particles in the mobility range 3.16 to 0.001 cm 2 /V / s, which corresponds to a mobility size range of 0.8 to 42 nm. The upper size detection limit of the NAIS effectively restricts it to the nanoparticle size range, which has somewhat arbitrarily been defined as smaller than 50 nm (Morawska et al, 2009). Therefore, all PNCs in this paper refer to nanoparticles only.…”

“…During such events, the PNC in the environment can increase from a few thousand cm -3 to over 1 × 10 5 cm -3 within time periods of 1-2 h (Woo et al, 2001). Most of the particles formed will be in the nanoparticle size range, that is, smaller than 50 nm (Morawska et al, 2009). Previous studies in Brisbane have shown that NPF is a regular occurrence (Cheung et al, 2011).…”