Waste dumps rehabilitation measures based on physico-chemical analyses in Zăghid mining area (Sălaj County, Romania)

The present study deals with an abandoned coal mine from Zăghid area, North-Western Transylvanian Basin (Sălaj County). The mining activity was stopped in 2005, without any attempt of ecological rehabilitation of the mined area and especially of the waste dumps left behind. The proposed rehabilitation models are based on some physical-chemical analyses of soil and waste samples (e.g. pH, EC, Salinity, humidity, porosity, density, plasticity, organic substances, mineralogical composition, heavy metals). Erosion map has been drawn based on the determined mineralogical composition (according STAS 1913/5-85 - using Galton curve) of tailings and the soil type. The values obtained for moisture and plasticity have been used to determine the ideal general inclination angle of the landfill systems in the studied perimeter. Through chemical analysis, heavy metals like Ni and Cu have been identified, as the main pollution factors for surface and underground water. Therefore, the concentration of heavy metals in the waters from Zăghid area is high in the water bodies, which are formed on waste dumps, but also in the mine water. This analysis is useful in establishing the actual state of the waste dumps and their content and the negative effects, which exercise on the environment in order to select the rehabilitation model for the waste dumps from Zăghid mining area. The main measures consist in: waste dumps leveling, soil remediation, perennial plants culture and acid mine water decontamination.