Regional Deposition of Submicrometer Aerosol in the Human Respiratory System Determined at 1-s Time Resolution of Particle Size Distribution Measurements

Pasquale Avino,Francesco Lopez,Maurizio Manigrasso

doi:10.4209/aaqr.2013.06.0189

Abstract

Submicrometer aerosol size number distributions have been measured in downtown Rome with 1 s time resolution. From these data, the particle deposition in the human respiratory system has been assessed for infants, children and adults under different exercise levels. The estimates are reported as size segregated percentages and as total particle numbers deposited. The greatest percentages of particles are deposited in the alveolar interstitial region. Deposited doses, expressed per unit body weight or per unit alveolar surface area, indicate that children and infants are more at risk than adults. Following vehicle exhausts, nucleation particle concentrations increase within a few seconds and decrease in the time scale of tens of seconds. In accordance with traffic cycles, such particles are very common during the day, and decrease at night, when accumulation mode particles are more prevalent. As a consequence, the exposure scenario, in proximity to traffic, may be represented by a sequence of short-term peak exposures. The appraisal of such brief exposures depends on the time resolution of measurements, being underestimated if aerosol measurements are performed with resolutions on the time scale of minutes. The health relevance of such exposure patterns needs to be investigated, and the relevant measurement averaging time should also be defined.

Highlights

We have carried out aerosol measurements fulfilling two fundamental requisites: the first is size resolution, since the deposition of particles into the human respiratory system is strictly related to their dimensions, the second is time resolution, comparable with the time scale of variation of aerosols deriving from combustion exhausts
Aerodynamic Diameter distributions during winter and summer periods in downtown Rome expressed as numerical and mass determinations. It can be seen how the fine mode is described by a distribution below 1 μm. This suggests that it is appropriate to measure the PM1 compared to PM2.5 as a descriptor of the fine mode (PM1 explains a significant and notable portion of PM2.5)
The particles in excess of 500–600 nm have a negligible influence on the distribution if expressed on a numerical basis, while if we refer to the concentrations in mass, they have a considerable importance in the accumulation mode and, and especially, in the coarse mode

Summary

Introduction

Among the different pollutants present in urban air (Monod et al, 2001; Avino and Manigrasso, 2008), an important role is played by the urban aerosol (Avino et al, 2000, 2002, 2003a, b; Lepore et al, 2003; Avino and Manigrasso, 2006; Avino et al, 2006; Avino and Manigrasso, 2007; Avino et al, 2008; Movassaghi et al, 2008; Manigrasso et al, 2010). Submicrometer aerosol size number distributions have been measured in downtown Rome with 1 s time resolution.

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Results

Conclusion