EVALUATION OF ORIGIN AND DISTRIBUTION OF WET DEPOSITION RECORDED IN THE SPANISH-BASQUE COUNTRY

Within the framework of the EPOCA programme (Estudios en el Pirineo Oc cidental de la Contaminacion Acida), wet deposition of inorganic pollu tants was measured at five rural sites in the Spanish Basque Country b etween Dec 85 and Apr 91. Na+, Ca2+, SO4exc2-, and NH4+ ions were the main species found in the rainwater samples. The average pH value rang ed between 4.9 and 5.6 depending on the site. Relationship between the ionic concentrations and the back-trajectories showed that trajectori es coming from Europe resulted in the highest NO3-, SO4exc2- and H+ co ncentrations. NO3- and H+ incursion in the study area by a long-range- transport phenomenon was estimated in 20 mu eq l(-1) for each ion. By means of both the one-way analysis of variance and the range tests for the wet deposition, two of the sites resulted to be able to represent both qualitatively and quantitatively the wet deposition collected at all sites.