Relationship between precipitation chemistry and meteorological situationsat a rural site in NE Spain

Bulk precipitation samples were collected at Montseny (Catalonia, NE Spain) from 1983 to 1994 and analysed for major cations and anions. The samples w ere classified for provenance based on meteorological synoptic maps and bac k trajectory analysis to identify the source areas of pollutants in precipi tation. The meteorological classification was compared to an independent gr ouping based on multivariate data analysis (Clustering and Principal Compon ent Analysis). Alkaline rain (mean pH = 7.2) was associated to African traj ectories. Local events produced neutral rains (mean pH = 5.5). Acid rain wa s associated to rains of Atlantic origin (mean pH = 4.8) and to European ra ins (mean pH = 4.4), which also presented the highest mean concentrations o f NH4+ (57 mu eql(-1)), NO3-(49 mu eql(-1)) and SO42-(103 mu eql(-1)). Howe ver, European events were only a small fraction of the total precipitation (10% of the cases). Marine rains accounted for 52% of the events, and Afric an and Local for 20 and 18%, respectively. During the 11 year period there was a decreasing trend for the frequency of European events. (C) 1999 Elsev ier Science Ltd. All rights reserved.