Potential contribution of distant sources to airborne Betula pollen levels in Northeastern Iberian Peninsula Alarcón, Marta De Linares Fernández, Concepción Pollen concentration peak and season Source regions Mesoscale and Lagrangian models Orography Role of long-range transport We acknowledge the financial support of the European Commission for ENV4-CT98-0755; the Spanish Government for CGL2004-21166-E, CGL2005-07543/CLI, CGL2009-11205, CGL2012-39523-C02-01/CLI, CGL2012-39523-C02-02, CGL2016-75996-R, CTM2017-89565-C2-1, CTM2017-89565-C2-2, and CSD 2007-00067; the Catalan Government for 2005SGR00519, 2009SGR1102, and 2017SGR1692; Diputacio de Tarragona; Servei Meteorologic de Catalunya; Sociedad Espanola de Alergologia e Inmunologia Clinica (SEAIC); Laboratorios LETI PHARMA; Societat Catalana d'Allergia i Immunologia Clinica (SCAIC); J Uriach y Compania; S.A. This research contributes to the Maria de Maeztu Programme for Units of Excellence of the Spanish Ministry of Science and Innovation (CEX2019-000940-M). The authors gratefully acknowledge the NOAA Air Resources Laboratory (ARL) for their HYSPLIT transport and dispersion model and the synoptic charts used in this publication. Betula (birch) pollen is one of the most important causes of respiratory allergy in Northern and Central Europe. While birch trees are abundant in Central, Northern, and Eastern Europe, they are scarce in the Mediterranean territories, especially in the Iberian Peninsula (IP), where they grow only in the northern regions and as ornamental trees in urban areas. However, the airborne birch pollen patterns in Catalonia (Northeastern IP) show abrupt high concentrations in areas with usually low local influence. The intensity of the derived health problems can be increased by outbreaks due to long-range pollen transport. The present work evaluates the different potential contributions to Catalonia from the main source regions: Pyrenees, Cantabria, and the forests of France and Central Europe. To this end, we computed the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) back trajectories of air masses associated with the main Betula pollen peaks occurring simultaneously over different Catalan monitoring stations, and we studied their provenance over a 15-year period. The Vielha aerobiological station on the northern slopes of the Central Pyrenees was used to identify the dates of the pollen season in the Pyrenean region. In order to better understand the role of the Pyrenees, which is the nearest of the four birch forested regions, we classified the pollen peaks in the other Catalan stations into three groups based on the relationship between the peak and the pollen season in the Pyrenees. Our analysis of back-trajectory residence time, combined with the associated pollen concentration, reveals that two principal routes other than the Pyrenean forest sustain the northerly fluxes that enter Catalonia and carry significant concentrations of Betula pollen. This study has also allowed quantifying the differentiated contributions of the potential source regions. In addition, theWeather Research Forecast (WRF) mesoscale model has been used to study three specific episodes. Both models, HYSPLIT and WRF, complement each other and have allowed for better understanding of the main mechanisms governing the entry of birch pollen to the region. 2022-05-19T08:20:19Z 2022-05-19T08:20:19Z 2021-11-20 info:eu-repo/semantics/article Marta Alarcón... [et al.]. Potential contribution of distant sources to airborne Betula pollen levels in Northeastern Iberian Peninsula, Science of The Total Environment, Volume 818, 2022, 151827, ISSN 0048-9697, [https://doi.org/10.1016/j.scitotenv.2021.151827] http://hdl.handle.net/10481/74915 10.1016/j.scitotenv.2021.151827 eng http://creativecommons.org/licenses/by-nc-nd/3.0/es/ info:eu-repo/semantics/openAccess Atribución-NoComercial-SinDerivadas 3.0 España Elsevier