10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Analysis of Particulate Atmospheric Matter Samples Collected with High Time Resolution: Some Examples of Recent Applications
FRANCO LUCARELLI, Giulia Calzolai, Massimo Chiari, Silvia Nava, Roy M. Harrison, Zongbo Shi, Di Liu, Bill Bloss, Van Tuan Vu, University of Florence and INFN Florence, Italy
Abstract Number: 1276 Working Group: Source Apportionment
Abstract The study of atmospheric particulate matter (PM) is an important issue, due both to the danger it poses to health and to its role in climate changes: these effects are strictly dependent on the chemical composition and the particle size. Most air quality studies on particulate matter (PM) are based on 24-h averaged data; however, many PM emissions as well as their atmospheric transport and dilution change within a few hours and daily samples are not capable of tracking these rapid changes. Elemental concentration obtained with 1-h time resolution can give invaluable information for the study of episodic events, lasting a few hours which may lead to an exposure problem like the ones occurring in industrial sites or during pyrotechnic events, such as on New Year’s Eve, national festivities, and light festivals. Source apportionment receptor models need a series of samples containing material from the same set of sources in differing proportions and increasing the time resolution of the measurements typically provides samples that have greater between-sample variability in the source contributions than samples integrated over longer time periods. Furthermore, a more direct correlation with wind direction and speed is possible, since on a daily scale the wind direction may have strong variations. Finally, the choice of the sampling sites, along the prevalent wind direction and in opposite position with respect e.g. an industrial site, allows to follow the impact of the plume as a function of wind direction.
Currently, there are only a few devices available on the market for sampling aerosol with hourly resolution. At LABEC laboratory at Florence (Italy) since many years we use the so called "streaker" samplers by PIXE International Corporation, which are designed to separate the fine (<2.5 μm) and the coarse (2.5–10 μm) fractions of PM. These samples are effectively analyzed in a short time by PIXE technique at the LABEC laboratory, equipped with a 3MV particle accelerator, thanks to an optimized external-beam set-up, a convenient choice of the beam energy and the choice of suitable collecting substrata.
Examples of recent application of the combined use of streaker samplers and PIXE analysis (eventually complemented by other hourly data) will be reported, regarding industrial sites, heavy polluted towns (like Beijing or Delhi) or natural events (like Saharan dust transport episodes).