Coarse-Particle Passive-Sampler Measurements and Single-Particle Analysis by Transmitted Light Microscopy at Highly Frequented Motorways

Abstract

Measuring and characterizing airborne particulate matter (PM) is an important research area because PM can lead to impacts on health and to visibility reduction, material damage and groundwater pollution. In regard to road dust, suspension and re-suspension and the contribution of non-exhaust PM to total traffic emissions are expected to increase as a result of predicted climate scenarios. European environmental regulations have been enforced to reduce exhaust particle emissions from road traffic, but little attention has been paid to reducing non-exhaust coarse particle emissions due to traffic. Therefore, a monitoring program for coarse PM has been initiated in early 2013 to assess the predicted increase in the abundance of non-exhaust particles. Particle sampling was performed with the passive-sampler technique Sigma-2. The subsequent single-particle analysis allows for characterization of individual particles, determination of PM size distribution, and calculation of PM mass concentrations. Two motorways near Cologne (Köln), Germany were selected as sampling sites, and the experimental setup in the field was realized with a so-called twin-site method. The present study reports single-particle analysis data for samples collected between May 31, 2013 and May 30, 2014. Coarse PM, generated through multi-source mechanisms, consists of, e.g., tire-wear, soot aggregates, and mineral dust. The highest mass concentration occurs at both motorways in spring, and the observed PM mainly contains traffic-abrasion particles. The field measurements show that the minimum PM concentration was found in the 5 to 12°C temperature range, whereas the maximum concentration was observed in both the -5 to 5°C and the 12 to 24°C ranges, in agreement with previous laboratory measurements. Correlation between super-coarse (d p 10-80 µm, geometric equivalent diameter) PM concentration and precipitation displays a significant increase in concentration with decreasing number of precipitation events (dry weather periods).

Confocal microscopy 3D imaging of diesel particulate matter

“…Several methods of imaging aerosol particles, other than confocal microscopy, have been listed by Li et al ( 2016 ). Indeed previous studies of the appearance of particulate matter have generally used 2D imaging such as investigations based on optical microscopy (Davis and Jixiang 2000 , Tian et al 2017 , Koval et al 2018 ), scanning electron microscopy (SEM) (Yang et al 2016 , Selley et al 2020 ), transmission electron microscopy (TEM) (Bérubé et al 1999 , Chandler et al 2007 , Liati et al 2012 ) or for 3D imaging of particles, stereo SEM (Mills and Rose 2010 ). Previous studies of diesel exhaust particulate morphology have often used SEM or TEM (Figler et al 1996 , Liati et al 2012 , Liati et al 2013 , Baldelli et al 2020 ).…”

Automated Microscopy Techniques on Passively Collected Samples Provide Reliable Quantitative Data on Airborne Pollen

“…A commercially available passive sampler, which collects particles based on the sedimentation principle, is the Sigma-2 sampler. It has demonstrated its applicability for airborne particulate matter monitoring in various recent studies (Norra et al, 2016;Sommer et al, 2018;Tian et al, 2017). The sampler is designed to collect particles with geometrical equivalent diameters between 2.5 µm and 80 µm quantitatively (VDI 2119(VDI , 2013.…”

Field comparison of dry deposition samplers for collection of atmospheric mineral dust: results from single-particle characterization

“…The Piskunov deposition veloc- ity model is made for flat surfaces, and therefore it is applied to the BSNE and flat-plate samplers, where deposition occurs to such surfaces. For the Sigma-2 sampler, it is assumed that each particle settles with the terminal settling velocity (Tian et al, 2017), and therefore Stokes velocity was used for calculation of concentrations. In the case of MWAC, a different approach was required due to its geometry.…”