* Corresponding authors

^a Institute of Earth Sciences “Jaume Almera”, CSIC, C/Lluís Sole i Sabarís s/n, Barcelona, Spain
E-mail: jpey@ija.csic.es
Fax: +00 34 93 4110012
Tel: +00 34 93 4095410

^b Instituto de Diagnóstico Ambiental y Estudios del Agua, IDÆA, CSIC, C/Jordi Girona, 18-26, Barcelona, Spain

^c Associate Unit CSIC-UHU “Atmospheric Pollution”, University of Huelva, Campus Univ. El Carmen, Huelva, Spain

^d Atmospheric Sounding Station “El Arenosillo”, INTA, Ctra. Huelva-Matalascañas, km 33, Huelva, Spain

^e Chemical and Environmental Engineering Department, Basque Country University, Alameda de Urquijo s/n, Bilbao, Spain

^f Department of Environment and Planning, University of Aveiro, Campus Univ. de Santiago, Aveiro, Portugal

^g Atmospheric Physics Group. Andalusian Center for Environmental Studies, CEAMA, University of Granada, Andalusia Regional Government, Granada, Spain

^h Departament of Applied Physics, University of Granada, Granada, Spain

ⁱ Atmospheric Optics Group, University of Valladolid, Prado de la Magdalena s/n, Valladolid, Spain

^j Instituto Universitario de Medio Ambiente, Universidade da Coruña, Pazo de Lóngora, Liáns-Oleiros, Coruña, Spain