The aim of this study is to interpret the variation of precipitation chemistry during the last 25 years in Montseny (NE Spain) by taking into account the main air mass transport routes and emission sources. To this end, trajectory cluster analysis and source-receptor models were applied to an early monitoring period (1984-1993) and compared to a more recent one (1998-2009). A decrease of Atlantic advections and increase of African and European air flows was found. Cluster analysis and source-receptor approaches showed that this region is under the influence of natural and anthropogenic sources from the local and long-range scale. Sulphate and H⁺ source areas extended over a vast stretch of central Europe in the early period, but were drastically reduced in the recent period, showing the effectiveness of pollution abatement measures for S. On the other hand, NO₃− sources areas from central Europe strikingly increased. Ship emissions and industrialisation in Eastern Europe and North Africa seem to be acquiring a greater role in the recent period.