The introduction of acid drainage to the river network is responsible for changing the physico-chemical characteristics of watercourses, increasing acidity in the water, the content of heavy metals and sulphates, and the concentration of metals in their sediments up to extreme values.
The main objective of this work is to characterize the behavior of As conditioned by the presence of other elements which are characteristic of AMD pollution, both in the generating milieu, and in the receiving milieu of the Tinto river, and thus to be able to establish the differences in behavior at both sites by using a fuzzy computer tool, PreFurGe, which allows qualitative interpretation of the data recorded in a database relating to the chemistry of water.
Fuzzy logic tools allow us to treat large data mass and to propose responses more consistent than those generated with classical statistics, to explain what determines the abundance of each parameter depending on the sampling point, as well as to notice interdependence relationships undetected with correlation analysis for a given watercourse.
With this study we observe that the extremely low As values are due to different circumstances at each sampling site: the pH in generating milieu may reach extremely high values while in receiving milieu it does not rise above medium-high values. The differences remain for extremely high As values, proving very much conditioned by the temperature in the generating milieu and only compatible with extremely high values for this, while in the receiving milieu it has barely any influence. It is the redox potential especially that presents a more pronounced difference, while in generating milieu it can have any value except extremely high and low, in receiving milieu we only find extremely low and very concentrated values
