Characterization of atmospheric aerosols at Monte Cimone, Italy, during summer 2004: Source apportionment and transport mechanisms

摘要

Atmospheric aerosols in the PM10 and PM1 fractions have been sampled at the GlobalAtmospheric Watch station Mount Cimone, Italy (2165 m above mean sea level) for3 months during summer 2004, and simultaneous size distributions have been derived bymeans of an optical particle counter. Samples have been analyzed by X-rayfluorescence, ion chromatography, and thermal-optical methodology in order to quantifytheir elemental, ionic, and carbonaceous constituents. The concentration of PM10 was16.1 ± 9.8 mg m3 (average and standard deviation). Source apportionment allowed us toidentify, quantify and characterize the following aerosol classes: anthropogenic pollution(10 mg m3), mineral dust (4 mg m3), and sea salt (0.2 mg m3). Pollution has beenfurther split into ammonium sulfate (44%), organic matter (42%), and other compounds(14%). The nitrate/sulfate ratio in the polluted aerosol was 0.1. Fine particles have beencompletely related to the polluted aerosol component, and they represented 70% in weightof pollution. Coarse particles characterized the dust and salt components, and crustaloxides have been found to be the largest responsible for the aerosol concentrationvariations that occurred during the campaign. Nitrate has also been found in the coarseparticles, representing 10% of mineral dust. The analysis of the transport mechanismsresponsible for aerosol fluctuations permitted us to identify the origin of the majoraerosol components: Pollution has been ascribed to regional transport driven by boundarylayer meteorology, whereas mineral dust has been related to long-range transport eventsoriginating in the Sahara and Sahel. A particularly significant Saharan episode hasbeen identified on 10 August 2004 (PM10 daily concentration, 69.9 mg m3). Averageelemental ratios for the African dust events were as follows: Si/Al = 2.31, Fe/Ca = 0.94,Ca/Al = 0.90, K/Ca = 0.44, Ti/Ca = 0.11, and Ti/Fe = 0.12.