Contamination factors of the groundwater of the Ervedosa region (NE Portugal)

Hugo Novais (Escola Secundária de Lousada, Rua Dr. Mário Soares, 194, 4620-493 Lousada, Portugal)
Maria do Rosário Pereira (Dep. de Geologia, UTAD, Apartado 1013, 5001-801 Vila Real, Portugal)
Carla Patinha (Dep. de Geociências, Univ. de Aveiro, Campus de Santiago, 3810-003 Aveiro, Portugal)
Eduardo Ferreira da Silva (same address as C. Patinha)

volume 5 - nº 7 - 2008

Key-words: groundwater, contamination, agriculture, domestic sewage, abandoned mines.

Abstract: In the Ervedosa region occurs a set of natural and human factors, which contribute to the decrease of the water quality, in what concerns its common uses, mainly human consumption and watering. The natural factors correspond to the presence of tin and arsenic mineralizations, associated with sulfides, in quartz veins. The human factors consist of abandoned mining exploitations of those resources, agricultural activities and population clusters which use effluent drainage through septic tanks. In this study springs and drilled wells were sampled, having been determined the content in HCO3-, Cl-, NO3-, SO42-, Na+, K+, Ca2+ and Mg2+. In the field the values for temperature, electrical conductivity, pH and redox potential were also determined. By analysing the results it is noticed the contamination of groundwater by nitrate, probably originated by the fertilizers used in agriculture, as well as chlorides, resultant from the drainage of animal excretions, mainly accumulated in septic tanks. The abandoned mining explorations, as well as the unexploited mineralizations, contribute to the increase of the ionic charge, mainly noticed through the increase of the electrical conductivity and the increase in SO42-.

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