title: Intense winter atmospheric pollution episodes affecting the Western Mediterranean.
abstract: The geographic location of the Western Mediterranean Basin and its peculiar topography, the climatic conditions and the intense anthropogenic and natural emissions of atmospheric pollutants are key factors necessary to interpret the atmospheric aerosol phenomenology over this area. During the cold season it is common to have severe atmospheric particulate matter (PM) pollution episodes (of an anthropogenic origin) affecting this region, not only in the urban and industrial areas but also in the regional and rural sites. During these episodes, the midday hourly PM(1) levels at regional background sites are in many cases higher than those at urban areas. Around 10% of the days under winter anticyclonic conditions registered similar PM(1) levels at the regional background than at the urban area and, sporadically the daily PM(1) levels at the regional background sites may exceed those at urban sites. Furthermore, the very high hourly PM(1) levels measured at regional background sites during these episodes are not regularly attained in the closest urban areas, which leads to the hypothesis that an important formation of secondary aerosols occurs during the transport of the polluted air masses towards the elevated rural sites. The interpretation of the variability of PM levels and composition (2002-2008) at one urban site (Barcelona) and at one regional background site (Montseny) allows us to illustrate the phenomenology of these scenarios, to quantify the mean annual contributions to the PM levels and to identify their main tracers. Ammonium nitrate appears to be the most abundant compound during these scenarios, although organic species and trace metals also increase markedly. Owing to the intensity, composition and recurrence of these atmospheric pollution episodes, important health, climatic and ecological implications may be derived.
authors.affiliation: Institute of Environmental Assessment and Water Research (IDAEA), Department of Geosciences CSIC, LLuis Solé i Sabarís S/N, Barcelona, Spain. jorge.pey@idaea.csic.es
authors.forename: Jorge
authors.initials: J
authors.lastname: Pey
authors.forename: Noemí
authors.initials: N
authors.lastname: Pérez
authors.forename: Xavier
authors.initials: X
authors.lastname: Querol
authors.forename: Andrés
authors.initials: A
authors.lastname: Alastuey
authors.forename: Michael
authors.initials: M
authors.lastname: Cusack
authors.forename: Cristina
authors.initials: C
authors.lastname: Reche
mesh_terms: D000336:Aerosols / Q000032:analysis*; D000392:Air Movements; D000397:Air Pollution / Q000032:analysis*; D001272:Atmosphere / Q000032:analysis*; D004784:Environmental Monitoring; D005843:Geography; D006801:Humans; D019083:Mediterranean Region; D052638:Particulate Matter / Q000032:analysis*; D011634:Public Health; D012621:Seasons; D013997:Time Factors
chemical_list: D000336:Aerosols; D052638:Particulate Matter