Journal of Electron Microscopy Advance Access published February 10, 2011 Journal of Electron Microscopy 0(0): 1–15 (2011) doi: 10.1093/jmicro/dfr001 ........................................................................................................................................................................................................................................................
Physical: Full-length
Electron microscopy characterization of airborne micro- and nanoparticulate matter Gustavo Capannelli1, *, Enrico Castello1, Antonio Comite1, Camilla Costa1 and Giuseppe Mamolini2 1
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Abstract
The aim of this work was to offer a state-of-the-art critical survey for characterizing airborne nano- and microparticles by means of electron microscopy (EM) techniques and to highlight advantages and limits of different possible operation modes. Procedures of collection and sample preparation are revisited and improved to analyse airborne particles deposited on filtering membranes by using various sampling methods. Three kinds of electron microscopes are used to this end: scanning electron microscope (SEM), field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM). Following and extending previous studies, we optimized procedures by varying both the sample collection/preparation and the operational parameters of the microscopes. In particular, we diversified the sampling methods applied, using ad hoc filters as well as common filters for standard gravimetric measures. This approach enabled us to achieve a simple and clean procedure allowing direct SEM or TEM observation of the collected particulate matter.
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Keywords
PM, nanoparticles, FE-SEM, TEM, PC filters, INCA-Feature software
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Received
2 April 2010, accepted 13 January 2011
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Introduction Air pollution due to nano- and microparticles is of increasing interest to both the scientific community and the general public. In this context, the acronym PM ( particulate matter) is used to denote solid and liquid particles (organic or inorganic) suspended in air (WHO). European Community (EC) directives dictate European Countries the introduction of laws setting air quality standards for PM10 and PM2.5, while the PM1 concentrations are at a preliminary stage of regulation. The acronyms PM10, PM2.5 and PM1 refer to particles of less than 10, 2.5 and 1 μm, respectively, in aerodynamic diameter, which is defined as the diameter of a sphere of unit density (1 g cm−3)
which has the same terminal falling speed in air as the particle of interest, at the same conditions of temperature, pressure and relative humidity. The quality standard for PM10 is referred to the maximum annual mean concentration, that is, 40 µg m−3, linked with the limit of 35 days in a year exceeding a daily mean concentration of 50 µg m−3 (European Standard EN 12341; for details on the reference method for sampling and measuring PM10, see [1]). Morphology and chemical composition are not referred to; however, it is becoming clear that these parameters are of great importance to the human health, particularly with regard to ultrafine particles or nanoparticles (
