Suman, Roberto (2012) Analisi PMF di spettri ATOFMS di singola particella per la caratterizzazione del particolato atmosferico. [Magistrali biennali]
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Atmospheric aerosol is defined as a suspension of solid and liquid particles in the atmosphere. Knowing its physical and chemical properties, composition and sources is of primary importance because of it causes short and long term adverse effects on human health and on the environment. For this purpose, sophisticated on-line mass spectrometry techniques, which allow size and chemical characterization of aerosol in real time, have been recently developed. Currently, the two commercially available instruments are the AMS (Aerosol Mass Spectrometer) and the ATOFMS (Aerosol Time of Flight Mass Spectrometer). In this work of thesis, the ATOFMS (TSI Model 3800-100) data, collected at Marylebone Road, a major traffic route in London (UK) city centre, which present the characteristics of a “street canyon”, are treated through the application of PMF analysis and K-means classification analysis. After a first optimization step of PMF analysis, in particular through a comparison between the results obtained from the application of the PMF analysis to the original data matrix (which contains many zero values) and to the data matrix to which a background noise was previously added, I have focused on the possibility to extract new factors through two different approaches. By scaling the input data through the square root a new factor characterized by two intense 56Fe and 54Fe signals was extracted. By applying PMF analysis to data matrix of similar composition, obtained from K-means classification analysis, a new factor representing calcium was extracted. However, the possible interference of the potassium miscalibrated signal could not be excluded. Finally, the results obtained from PMF and K-means analysis applied on the entire dataset were correlated with the meteorological and vehicular traffic count data in order to make a source apportionment study.
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