Roxana Bostan

Mining activities have a significant impact on the quality of river water in the Roșia Montană area. This region, known for its gold and other precious metal mining, serves as an example of the interaction between anthropogenic activities and the natural environment. Water from mine drainage is metal-rich and contaminates the environment, inhibiting the growth and reproduction of aquatic plants and animals, while also having corrosive effects on infrastructure. As part of the study, parameters such as pH, dissolved oxygen, biochemical oxygen demand, chemical oxygen demand, sulfates, and heavy metals were monitored for the rivers in the area (Roșia Montană, Săliște, Corna, Abrud, and Arieș). Roșia Montană river shows a decrease in pH to highly acidic values (2.69–3.95), especially in the downstream sections. Sulfate concentrations exceed 3600 mg/L, and heavy metal concentrations (Fe, Zn, As, Mn) increase significantly, indicating severe pollution, primarily originating from the Gura Mine gallery. These frequently exceed the thresholds corresponding to water quality classes I and II, and in some cases even surpass the limits of class V (the most polluted). The presence of As (27.60 µg/L) in Roșia Montană River indicates a significant ecotoxicological risk. In an attempt to treat the acid mine drainage from Roșia Montană, a natural zeolite was used at different doses. The results obtained show good efficiency of zeolite in removing the metal ions (Fe, Zn, and Mn). The results provide valuable information on the quality of river waters in the mining area of Roșia Montană and suggest that zeolite can be used effectively to decontaminate mine waters.

Contamination with heavy metal ions from mining activities presents a major environmental issue. This study investigates pollution caused by heavy metals from mining, with a particular emphasis on toxic ions and essential ions for living organisms. It starts by analyzing the sources of pollution and its effects on soil, vegetation, water, and wildlife (propolis produced by honey bees living in natural environments). Propolis is an indicator of environmental contamination by metals, a natural and valuable product of natural ecosystems. As part of the investigation, the contamination with metal cations (Pb²⁺, Cu²⁺, Cd²⁺, Zn²⁺, As³⁺, Fe²⁺, and Sr²⁺) of the soil, cultivated vegetables (carrot, turnip, onion, potato) was monitored in 9 points in the Roșia Montană area, Romania, as well as the river that runs through the area. The maximum values of the parameters investigated were recorded in soil (108.32 mg/kg Pb²⁺, 23.06 mg/kg Cd²⁺, 102.17 mg/kg As³⁺), river water (11.00 µg/L Pb²⁺, 903.47 µg/L Cu²⁺, 60.13 µg/L Cd²⁺, 1903.08 µg/L Zn²⁺, 148.07 µg/L As³⁺, 44,024.08 µg/L Fe²⁺), vegetables (0.72 mg/kg Pb²⁺, 0.17 mg/kg Cd²⁺) and it was followed whether the same heavy metals are found in propolis (maximum values 10.14 mg/kg Pb²⁺, 6.32 mg/kg Cu²⁺, 0.158 mg/kg Cd²⁺, 6.0 Zn²⁺, 1.04 mg/kg As³⁺, 12.06 mg/kg Sr²⁺). The parameters analyzed for the river waters were pH, sulfates, the oxygen and nutrient regime, and microbial load. Additional investigations were carried out into the quality of these propolis samples: water activity, moisture, hygroscopicity, water solubility, volatile oils, oxidation index, measuring point, density, dry matter, material insoluble in ethanol, extractable with ethanol, ash, and wax. The highest values were 189.4 mg GAE/g for phenols, 84.31 mg QE/g for flavonoids, and 0.086 µg/mL for IC₅₀ antioxidant activity. This study indicates that bee products, such as propolis, can be an indicator of pollution in mining areas.

The purification of used oils and their introduction into production cycles lead to reduction in environmental contamination. A simulation was conducted to study the thermal degradation of sunflower oil under varying temperatures over time. In the purification process of used cooking oil, an adsorption technique using zeolite and eggshell as an adsorbent (5, 10, 20, and 30 g/100 mL used oil) was applied. To optimize purification, different doses of thermally and chemically activated adsorbents were used, at different temperatures (30 and 80 °C). Therefore, this study was conducted in batch operations to determine the effect of suitable adsorption for a contact time of the adsorbent of 2 h. In comparison, the purification of used vegetable oils was achieved using a saline solution. The adsorption capacity was evaluated by determining the physicochemical parameters of the oils before and after purification. The characterization of natural adsorbents was carried out using scanning electron microscopy (SEM) and X-ray fluorescence spectrometry (XRF). The results showed that the adsorbent in a dose of 30 g of zeolite activated with NaOH and heat-treated eggshell, respectively, exhibited a larger surface area and greater adsorption capacity. Adsorption increased with contact time. The FT-IR spectra of the oils showed the IR bands at 1097, 1160, and 1237, corresponding to the presence of the ester C-O-, 1743 for C=O ester, 2853, 2922 for (CH₂, CH₃), and 3008 for (C=C). The acidity and peroxide values decreased with increasing dose and contact time with zeolite or eggshell. Together, our result strongly suggests that natural adsorbents contribute to the purification of used oils.

The purpose of this study was to review the physicochemical characterization of Romanian honey and propolis and their antifungal effect on different strains. As an indicator of environmental pollution, lead exceeded the allowed limits in two study areas. The relationship between the acidity and electrical conductivity of polyfloral honey and the antioxidant activity with the total content of phenolics and flavonoids was investigated. The antifungal activity of 13 polyfloral honey and propolis samples from North-West and Central Romania and 12 samples from Alba County was investigated against six fungal strains: Aspergillus niger, Aspergillus flavus, Candida albicans, Penicillium chrysogenum, Rhizopus stolonifer, Fusarium oxysporum. All honey and propolis samples exhibited an antifungal effect. The most sensitive strains were P. chrysogenum and R. stolonifer for honey and P. chrysogenum and F. oxisporumn for propolis. A two-way analysis of variance was used to evaluate the correlations between the diameter of the inhibition zones for the strains and the propolis extracts. Statistical analysis demonstrated that the diameter of the inhibition zone was influenced by the strain type and the geographical origin of honey and propolis. Pearson’s correlation coefficient shows a significant positive linear relationship between the diameter of the inhibition zone and the flavonoid and phenol concentration of honey and propolis, respectively.

The dissolution of the main metals (Cu, Zn, Sn, Pb and Fe) found in waste printed circuit boards (WPCBs) was investigated by electrochemical corrosion measurements (potentiodynamic polarization and electrochemical impedance spectroscopy (EIS)) in different bromide-based systems that could be used as lixiviants in hydrometallurgical route of metals recovery. The analysis of the corrosion products was carried out by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements. All measurements showed that the addition of bromine in the electrolyte favors to great extents the dissolution process of all studied metals as compared to bromine-free electrolytes. In the investigated experimental conditions, the highest dissolution rates of the metals were obtained in acidic KBr solution containing 0.01 mol/L bromine and they decreased in the following order: Zn >> Sn > Pb > Fe > Cu. The XRD and XPS chemical assessment allowed the identification of the dissolution products formed on the metallic surfaces after exposure to the electrolytes. They consisted mainly of oxides in the case of Cu, Zn, Sn and Fe, while the presence of PbBr₂ was also noticed on the lead surface. Based on the results of EIS and surface investigations, several models explaining the corrosion behavior of the metals were proposed and discussed. The obtained results demonstrate that all studied metals could be successfully leached using brominated solutions, providing a viable alternative for the selective and efficient recovery of the base metals from WPCBs through a multi-step hydrometallurgical processing route.