Origin of the exceedances of the European daily PM limit value in regional background areas of Spain

Long-range transport of PM from continental Europe caused exceedances (9-40% and 18-38% of the PM10 and PM2.5 exceedances, respectively), only in northern Iberia because, as the European air masses evolve towards the south, the pollutants suffer dispersion/dilution. Local exceedances are associated with the advection of the clean Atlantic air masses, which cannot increase PM levels to a great extent without the influence of a local source of PM. The proportion of local exceedances of PM10 and PM2.5 ranged 6-33% and 17-40%, respectively.