Application of a short-term method and analysis of atmospheric particulate samples via SEM-EDX

This study aimed to develop a method of short-term sampling (60-120 minutes) and subsequent chemical and morphological analysis of PM (Particulate Matter) by scanning electron microscopy and energy dispersive spectroscopy (SEM-EDX). The PM samplings (respirable PM fraction - PM4) were carried out through a filter-based technique at a traffic site and a rural site (and related background sites). The analyses of the collected filters, aimed at the chemical and morphological characterization of the particles, were performed via SEM-EDX, after metallization. The applied sampling and analysis methods proved to be adequate for the study conducted and the objectives set. The sampling times used for this study made it possible to obtain a sample characterized by an optimal number of particles for the analysis. The characterization of the sample was therefore complete and exhaustive, making it possible to determine the morphologies and identify the particulate “classes” (in terms of compositional characterization) most present in the investigated sites. Based on the results of this study, it is possible to state that the choice of a sampling time (60-120 min) shorter than the typical sampling period used in other studies (up to 24h) based on a characterization of the PM via SEM-EDX was a valid choice for the purposes of the analysis. The sampling time of 60-120 minutes was in fact optimal for subsequent analyses, as it made it possible to (i) obtain a heterogeneous and representative sample, (ii) characterized by a PM load suitable to allow a correct chemical-morphology characterization of particles. Starting from the study reported here, one of the possible developments could be that of the application of the experimental design in other contexts, alerted by high temporal variability of exposure concentrations to PM, such as occupational contexts.