Preliminary Results of a Risk Assessment Study for Uranium Contamination in Central Portugal

Abstract

The Central region of Portugal contains a large number of U-mineral occurrences and 60 abandoned uranium mines exploited since 1907. The U mineralisation is mainly hosted in granitic rocks, naturally radioactive. Thus, the objective of this study is to evaluate the risk for population of the mining explorations and unexploited mineralisations. The study consisted of two units approach, one, where specific regional indicators: land use, lithology, natural gamma radiation, geoaccumulation index of uranium in stream sediments, distance from uranium mines to land use categories, and a classification of mines based on: type of exploitation, Volume of waste, leaching and acid water presence, are used as hazard potential. Vulnerability was considered as a ``number of inhabitants per water system.{''} Another approach uses municipality as unit (NUTS IV) where the hazard potential is characterised by the number of mines per municipality, water system per municipality, inhabitants per water system, and the classification of mines. The vulnerability was divided in damage potential and coping capacity, damage potential is regional gross domestic product (GDP) per capita and population density and coping capacity is number of doctors per 1,000 inhabitants and national GDP per capita. In tile first approach, the areas enriched are bigger than the mining areas, meaning that natural radioactivity can be important in this hazard characterization. In the second approach, the higher risk municipalities have open pit uranium mines with acid mine drainage, high volumes of waste materials and medium population density, GDP per capita and less doctors per 1,000 inhabitants. These municipalities are Gouveia, Guarda, Mangualde. The results are conditioned by the available data to introduce in the study, specially the vulnerability data that may change with time.