Water resources monitoring and mine water control in Portuguese old uranium mines

摘要

Environmental rehabilitation of old abandoned mines in Portugal in done since 2001 by EDM -Empresa de Desenvolvimento Mineiro, a state-owned company, of 175 abandoned mining areas, 61 of which in radioactive minerals and 114 in polymetallic sulphides. By the year of 2015, 95 mining areas have been intervened of a total of 175 and ten are with ongoing remediation works.Monitoring the water environment is a relevant activity in the work developed in radioactive mines, started since 2002, which includes measuring in situ parameters and laboratory analysis of chemical and radiological parameters as total uranium, radium-226, sulphates, chlorides, manganese, calcium and sodium, these already identified in previous studies to be the best indicators of hydrochemical contamination related to the old uranium mining areas. Water resources monitoring plan covers upstream and downstream surface water samples, groundwater samples through wells, boreholes and piezometers in the surrounding mine area, together with the quality control of mine water before and after treatment. Per year a total of around 1260 water samples are collected in 61 radioactive mines. Denser monitoring plan in terms of sampling points and monitoring frequency is dependent on the level of contamination of each mine.The main objective of this paper is to present some details and example results of the work performed by EDM regarding the water resources monitoring plan and control of mine water effluents implemented in the radioactive mines. One of the main focus of remediation design projects is the control and treatment of mine water using passive treatment systems. EDM is implementing this type of systems with demonstrated success, in some cases associated with groundwater natural attenuation processes for uranium, radium-226 and other metals.