Source identification and variation in the chemical composition of precipitation at two rural sites in France

A receptor-oriented model is developed to identify and locate the sources of the constituents present in precipitation collected at two rural French stations, namely Donon and Morvan. Firstly, factor analysis is applied to the chemical data sets. Three factors are identified reproducing the concentrations observed in precipitation. These factors represent the acid sources (characterized by the ionic combination between H+, SO42− and NO3−), marine sources (Na+, Cl− and Mg2+) and crustal sources (Ca2+ and K+). Then, the factor scores of samples are combined with the air parcel back trajectories in the same scheme of model calculation to produce the probability maps of source locations. This approach, called potential source contribution function (PSCF) analysis, locates the acid sources in the industrial areas of Northeastern Europe and Great Britain, the marine sources in the Atlantic Ocean and the crustal sources around the Mediterranean Basin. The seasonal profiles of these factors are performed and contrasted with the atmospheric processes and meteorological conditions which prevail in each season. A classification of these daily samples is also made according to four origin sectors, to examine the variations in ionic composition of precipitations from one sector to another. The results of this classification are in agreement with the source locations found by the PSCF analysis.