Geochemical study of surface waters in mountain granitic area. The Iskar upper watershed: Massif of Rila, Bulgaria

The aim of this study is to determine the characteristics of the Iskar upper watershed surface waters as a first step of a seasonal evolution study. The geochemical and petrochemical characteristics of the Rila massif are well-suited to study the relative significance of different weathering mechanisms occurring along the year in a mountain aquatic system. In such an area the atmospheric input contribution to the surface water quality could be assessed. A first sampling survey in summer-time allowed us to get some data on major and minor elements in the soluble phase. The results show that the Iskar upper watershed is well-suited because of no mixing with long residence time groundwaters and of the low population density which results in insignificant anthropic input.