Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 5 10 2005 10.5194/acp-5-2739-2005 http://www.atmos-chem-phys.net/5/2739/2005/ http://www.atmos-chem-phys.net/5/2739/2005/acp-5-2739-2005.html http://www.atmos-chem-phys.net/5/2739/2005/acp-5-2739-2005.pdf 2739 2748 2005-10-19 Morphological, chemical and optical absorbing characterization of aerosols in the urban atmosphere of Valladolid S. Mogo V. E. Cachorro A. M. de Frutos Grupo de Óptica Atmosférica, Universidad de Valladolid, Valladolid, Spain Dep. de Física, Universidade da Beira Interior, Covilhã, Portugal Samples of atmospheric aerosol particles were collected in Valladolid, Spain, during the winter of 2003-2004. The measurements were made with a Dekati PM10 cascade impactor with four size stages: greater than 10 µm, between 2.5 to 10 µm, 1 to 2.5 µm and less than 1 µm. The size and shape of the particles were analyzed with a scanning electron microscope (SEM) and elemental analysis was done with an energy dispersive x-ray analysis (EDX). We present an evaluation by size, shape and composition of the major particulate species in the Valladolid urban atmosphere. The total aerosol concentration is very variable, ranging from 39.86 µg·m-3 to 184.88 µg·m-3 with the coarse particles as the dominant mass fraction. Emphasis was given to fine particles (<1 µm), for which the visible (400 nm to 650 nm) light absorption coefficients were measured using the integrating plate technique. We have made some enhancements in the illumination system of this measurement system. The absorption coefficient, σa, is highly variable and ranges from 7.33×10-6 m-1 to 1.01×10-4 m-1 at a wavelength of 550 nm. There is an inverse power law relationship between σa and wavelength, with an average exponent of -0.8.