title: Nitrogen oxides and ozone in Portugal: trends and ozone estimation in an urban and a rural site.
abstract: This study provides an analysis of the spatial distribution and trends of NO, NO2 and O3 concentrations in Portugal between 1995 and 2010. Furthermore, an estimation model for daily ozone concentrations was developed for an urban and a rural site. NO concentration showed a significant decreasing trend in most urban stations. A decreasing trend in NO2 is only observed in the stations with less influence from emissions of primary NO2. Several stations showed a significant upward trend in O3 as a result of the decrease in the NO/NO2 ratio. In the northern rural region, ozone showed a strong correlation with wind direction, highlighting the importance of long-range transport. In the urban site, most of the variance is explained by the NO2/NOX ratio. The results obtained by the ozone estimation model in the urban site fit 2013 observed data. In the rural site, the estimated ozone during extreme events agrees with observed concentration.
authors.affiliation: Department of Physics (IMARENAB), University of León, León, 24071, Spain.
authors.forename: José Manuel
authors.initials: JM
authors.lastname: Fernández-Guisuraga
authors.affiliation: Department of Physics (IMARENAB), University of León, León, 24071, Spain.
authors.forename: Amaya
authors.initials: A
authors.lastname: Castro
authors.affiliation: Centre for Environment and Marine Studies, Department of Environment, University of Aveiro, 3810-193, Aveiro, Portugal.
authors.forename: Célia
authors.initials: C
authors.lastname: Alves
authors.affiliation: Department of Physics (IMARENAB), University of León, León, 24071, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Calvo
authors.affiliation: Centre for Energy, Environmental and Technological Research (CIEMAT), Department of Environment, 28040, Madrid, Spain.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Alonso-Blanco
authors.affiliation: Department of Physics (IMARENAB), University of León, León, 24071, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: Blanco-Alegre
authors.affiliation: Centre for Environment and Marine Studies, Department of Physics, University of Aveiro, 3810-193, Aveiro, Portugal.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Rocha
authors.affiliation: Department of Physics (IMARENAB), University of León, León, 24071, Spain. roberto.fraile@unileon.es.
authors.forename: Roberto
authors.initials: R
authors.lastname: Fraile
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D009589:Nitrogen Oxides / Q000032:analysis*; D010126:Ozone / Q000032:analysis*; D011174:Portugal
chemical_list: D000393:Air Pollutants; D009589:Nitrogen Oxides; D010126:Ozone
keywords: Generalized linear model; Nitrogen oxides; Ozone; Portugal; Rural background; Urban traffic