Boreal environment research 18: 19–36 © 2013 issn 1239-6095 (print) issn 1797-2469 (online) helsinki 31 January 2013 Editor in charge of this article: Veli-Matti Kerminen Deterioration of air quality across sweden due to transboundary agricultural burning emissions admir c. t argino 1) , Patricia Krecl 2) , christer Johansson 2) , erik swietlicki 3) , andreas massling 4) , Guilherme c. coraiola 1) and heikki lihavainen 5) 1) Federal Technological University of Paraná, Av. dos Pioneiros 3131, 86036-370, Londrina, Brazil 2) Department of Applied Environmental Sciences, Stockholm University, Svante Arrhenius väg 8, SE-114 18, Stockholm, Sweden 3) Division of Nuclear Physics, Lund University, Professorsgatan 1, SE-221 00 Lund, Sweden 4) Department of Atmospheric Environment, Aarhus University, Frederiksborgvej 399, DK-4000, Roskilde, Denmark 5) Finnish Meteorological Institute, Erik Palménin aukio 1, FI-00101 Helsinki, Finland Received 23 Dec. 2011, inal version received 9 Apr. 2012, accepted 13 Apr. 2012 targino, a. c., Krecl, P., Johansson, c., swietlicki, e., massling, a., coraiola, G. c. & lihavainen, h. 2013: Deterioration of air quality across sweden due to transboundary agricultural burning emissions. Boreal Env. Res. 18: 19–36. We analyzed measurements of aerosol and trace-gas concentrations from sites across Sweden before and during a series of agricultural wildland ires in eastern Europe in spring 2006. During the burning episodes, concentrations of background particulate matter (PM) and trace gases, such as carbon monoxide and ozone, increased, affecting air qual- ity across the country and violating national air quality standards. The European Union PM 10 daily limit value of 50 µg m –3 was exceeded during the pollution episodes even at the background stations, resulting in a nearly four-fold increase as compared with that in non-episode conditions. In relation to a non-episode period, the concentration rise in the accumulation-mode particles was from 40% at an urban site to 340% at a rural site, causing an increase in total particle number concentrations. The ires also boosted ground- level ozone, increasing concentrations of this pollutant by up to 100% at the background stations, which exceeded national air quality standards. Both elemental (EC) and organic carbon (OC) levels increased, with OC making a larger contribution to the total carbona- ceous concentrations during the biomass burning episodes. The large-scale atmospheric circulation determined the strength and timing of the pollution events, with the eastern and northern sectors of Sweden experiencing two pollution pulses, whilst sites in the western and southern sectors were affected by one shorter episode. The results show that regional air quality deteriorated due to the long-range transport of pollutants emitted during agricul- tural wildires. Introduction Populations living in or around urban conglom- erates are usually exposed to increased concen- trations of air pollutants as a result of anthro- pogenic activities. Even though many countries adopted regulations to control the amount of certain pollutants discharged to the atmosphere,