title: Unexpected increase in the oxidation capacity of the urban atmosphere of Madrid, Spain.
abstract: Atmospheric oxidants such as ozone (O3), hydroxyl and nitrate radicals (OH and NO3) determine the ability of the urban atmosphere to process organic and inorganic pollutants, which have an impact on air quality, environmental health and climate. Madrid city has experienced an increase of 30-40% in ambient air O3levels, along with a decrease of 20-40% in NO2, from 2007 to 2014. Using air pollution observations and a high-resolution air quality model, we find a large concentration increase of up to 70% and 90% in OH and NO3, respectively, in downtown Madrid (domain-wide average increase of 10% and 32% for OH and NO3, respectively). The results also show an 11% reduction in the nitric acid concentrations, leading to a remarkable denoxification of this urban atmosphere with implications for lower PM2.5levels and nitrogen input into ecosystems. This study suggests that projected worldwide NOxemission reductions, following air quality standards, will lead to important changes in the oxidizing capacity of the atmosphere in and around large cities.
authors.affiliation: Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Rocasolano, CSIC, Madrid, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Saiz-Lopez
authors.affiliation: Laboratory of Environmental Modelling, Department of Chemical and Environmental Engineering, Escuela Técnica Superior de Ingenieros Industriales, Technical University of Madrid (UPM), Madrid, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Borge
authors.affiliation: University of Castilla-La Mancha, Physical Chemistry Department, Faculty of Chemical Science and Technologies, Ciudad Real, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Notario
authors.affiliation: Atmospheric Sounding Station-El Arenosillo, National Institute for Aerospace Technology (INTA), Atmospheric Research and Instrumentation Branch, Mazagón-Huelva, Spain.
authors.forename: J A
authors.initials: JA
authors.lastname: Adame
authors.affiliation: Laboratory of Environmental Modelling, Department of Chemical and Environmental Engineering, Escuela Técnica Superior de Ingenieros Industriales, Technical University of Madrid (UPM), Madrid, Spain.
authors.forename: D de la
authors.initials: D
authors.lastname: Paz
authors.affiliation: Institute of Environmental Assessment and Water Research, CSIC, Barcelona, Spain.
authors.forename: X
authors.initials: X
authors.lastname: Querol
authors.affiliation: Environmental Department of the Research Center for Energy, Environment and Technology (CIEMAT), Madrid, Spain.
authors.forename: B
authors.initials: B
authors.lastname: Artíñano
authors.affiliation: Environmental Department of the Research Center for Energy, Environment and Technology (CIEMAT), Madrid, Spain.
authors.forename: F J
authors.initials: FJ
authors.lastname: Gómez-Moreno
authors.affiliation: Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Rocasolano, CSIC, Madrid, Spain.
authors.forename: C A
authors.initials: CA
authors.lastname: Cuevas
mesh_terms: D001272:Atmosphere; D002947:Cities; D005843:Geography; D017665:Hydroxyl Radical / Q000032:analysis; D008962:Models, Theoretical; D009566:Nitrates / Q000032:analysis; D009569:Nitric Oxide / Q000032:analysis; D009573:Nitrites / Q000032:analysis; D016877:Oxidants; D010084:Oxidation-Reduction; D010126:Ozone / Q000032:analysis; D013030:Spain
chemical_list: D009566:Nitrates; D009573:Nitrites; D016877:Oxidants; D009569:Nitric Oxide; D017665:Hydroxyl Radical; D010126:Ozone