From December 2003 to June 2004 approximately weekly aerosol samples were collected in Valladolid, Spain. Gravimetric measurements were performed on the four particulate matter fractions: TSP, PM10, PM2.5 and PM1. The samples were analyzed for major ions by ion-chromatography. The optical properties of the fine particles are studied through the absorption coefficients, σa, in the visible range and the spectral shape of σa was analyzed by deriving a parameter, αa, similar to the Ångström exponent used for the extinction. Aerosol properties are classified according to their dependence on air mass origin.info:eu-repo/semantics/publishedVersio
