Opis: Mining in both Mežica zinc and lead mine and in Freixeda gold mine caused negative environmental impacts. The main objective of the thesis was to study negative impacts on water quality through time. During the process various literature sources were studied, field work and chemical analyses were performed and interpretation of results with different statistical methods was done.
In Mežica mine the quality of surface water has improved through time and nowadays the Meža River is of good quality. The biggest change was shown in the case of Helena rivulet, where Pb, Zn and Cd concentration between 2002 and 2015 lowered below limit values. Preventive measures and treatment of waste deposits had positive impact on water quality and based on standards for drinking water, groundwater from mine could be a source of drinking water. In Freixeda stream concentration of heavy metals lowered through time and in 2015 values of Zn, Pb, Cd and Cu in Freixeda stream before confluence with the Tua River were below the limit value. An exception is the increased value of As, which was caused by acid mine drainage (AMD) inflow from the mine, but also by the discharge from confined aquifer to Freixeda stream. Treatment of AMD was efficient for a while but due to lack of maintenance it is no longer effective.Najdeno v: osebiKljučne besede: Abandoned mines, heavy metals, pollution, Mežica mine, Freixeda mineObjavljeno: 05.10.2015; Ogledov: 2349; Prenosov: 149 Polno besedilo (4,82 MB)
Opis: Arsenic contamination in natural water is a worldwide problem and a major health concern. In master thesis hydrogeochemistry and toxicity effects of natural waters rich in arsenic were studied. The main objective of the master thesis was to evaluate As pollution of the Freixeda stream and groundwater in abandoned Freixeda gold mine area in NE Portugal near Mirandela city (41.413767 N 7.103562 W) and compare it with the data from previous studies. Further on, toxicological evaluation of selected water samples was performed in the in vitro system of human cell line Caco-2.
Chemical analyses of sampled water samples with use of different modelling sofware show that groundwater have higher sulphate and bicarbonate values than surface water, which could be the reason for As desorption and higher As values in groundwater. Water-rock interaction promotes reduction and dissolution of sulphide minerals and in reductive environments dissolution of secondary Fe minerals releases adsorbed As into solution.
Toxicological testing on human cells included cytotoxicity assay, genotoxicity assay and production of reactive oxigene species (ROS). Genotoxicity was only modestly affected by a short-term exposure to As-contaminated water samples, however, higher concentrations of As in real samples lead to higher level of oxidative stress and decreased cell viability. Exposure of cells to pure As(III) solution show clear concentration dependent decrease in cell metabolism and viability, strong genotoxicity and increased ROS generation.
Considering the worldwide extent of As contamination in natural waters and ability of intestinal epithelium to reduce the potential harmful effects of As, more studies evaluating the human intestinal permeability for As should be done in the future.Najdeno v: osebiKljučne besede: Water quality, arsenic, hydrogeochemistry, toxicity, Caco-2 cell lineObjavljeno: 26.09.2018; Ogledov: 602; Prenosov: 46 Polno besedilo (3,76 MB)