Identification of soil, vegetation and water characteristics by physical – chemical methods

Abstract

Heavy metals in water, soil, sediment and vegetation have become a global problem as a result of the increase of industrial activity in the last decades. Due to their toxicity, cumulative and non-biodegradable characteristics, heavy metals are potentially hazardous to terrestrial and aquatic ecosystems and therefore to the lives of humans and animals. Soil degradation as a result of mining for coal extraction, precious metals and due to ballast-type exploitation is the worst form of pollution because soil destruction occurs on large areas. Mining operations are areas of potential risk of pollution with toxic metals on the environment, both by accidental discharge of mine water, acidic water with a high content of metals, and through the deposits of mining waste, where there may be seepage into the underground and / or canvas. surface water. Even if the mine has been closed for a long time, metal pollution may continue. Thus, in the case of a closed mining operation, the rainwater or snow continued to wash the abandoned mine galleries and the dumps for mining waste, later pouring into the nearest river. Due to the acidity of these waters and the high content of toxic metals (As, Cd, Cr, Cu, Mn), both soil, surface water and sediments are highly contaminated and devoid of aquatic organisms. The in-depth study of environmental factors in the areas bordering some mining operations may indicate the presence of toxic impurifiers above the maximum limits allowed by the legislation in force, it may alert the population in the area of the danger of use, for example of contaminated groundwater, it may support a starting point for further decontamination of the area. Such a study can also estimate the extent of the polluted area, as well as the affected environmental compartments, surface water, groundwater, soil, sediment, vegetation. Heavy metals fall into two basic categories: essential and non-essential. Essential metals or micronutrients, such as chromium (Cr), cobalt (Co), copper (Cu), manganese (Mn), molybdenum (Mo), iron (Fe), selenium (Se) and zinc (Zn), are required for optimal functioning of biological and biochemical processes in organisms (including humans) including redox reactions and pigment and enzyme formation. Non-essential metals such as arsenic (As), cadmium (Cd), mercury (Hg) and lead (Pb) have no known biological function. Essential metals, at high concentrations, can have toxic effects on species and ecosystems. Like most organic pollutants, not even heavy metals are usually removed by natural processes [4]. The metals Palladium (Pd), Platinum (Pt), Rhodium (Rh), Ruthenium (Ru), Iridium (Ir) and Osmiu (Os) are known as the platinum element group (PGEs) or the platinum metal group (PGMs). These elements are classified, together with gold and silver, as noble or precious metals, which highlights the high value of these elements. Platinum metals are found in nature in small quantities, the most abundant is platinum and the least abundant is ruthenium. Platinum metals, due to their properties (corrosion resistant, high melting point, mechanical strength, ductility) are used mostly as catalytic converters but also in the glass, oil, electricity and electronics industries and in the manufacture of jewelry. Platinum metals are also used in medicine for the treatment of cancer (cisplatin complex PtCl2 (NH3) 2 is a wellknown anticancer drug), as well as for the preparation of dental vials. In the last decade, the concentration of platinum metals from environmental samples such as soil, surface water, sediments and vegetation has increased significantly, the main source of contamination with these platinum metals being the catalytic converters (components of cars fitted to the gas exhaust system). and which have a catalyst whose role is to transform the polluting gases the car produces: it converts carbon monoxide, nitrogen oxides and hydrocarbons into less dangerous compounds such as water, carbon dioxide and nitrogen). Catalysts containing platinum metals are used mainly in motor vehicles but can also be used in industry as stationary catalysts used for ammonia oxidation. The main sources of platinum metal emission in Europe: 50.4% come from catalysts, 24.7% from jewelry, 6% from the electrical industry, 4.8% from the chemical industry, 4.6% from the glass industry, 2.6% from the oil industry and 6.8% from other sources [5]. Human activity resulted in an increase in the concentration of PGE in the soil, especially in areas with high traffic, as evidenced by a number of international studies [6]. The results of the determination of PGE in the samples taken from areas near the roads / highways indicate a decrease in the concentration of platinum metals as the distance from the highways / highways increases. Increased concentrations of platinum metals were found in different water samples (rainwater, groundwater, surface water, marine sediments), these concentrations being caused by the emission of exhaust gases. Large concentrations of platinum have been found near the mines, especially those extracting nickel ores. Due to the fact that PGEs are mainly emitted in metal form, they exhibit low toxicity. Some of them are transformed into a soluble form, becoming bioavailable and dangerous for both flora and fauna. The doctoral thesis brings original contributions by evaluating polluted areas following the activities of the mining and transport industries and the potential of transfer of metallic pollutants into ecosystems through an in-depth study of the environmental compartments (surface water, sediment, soil and vegetation) from a river sector and its tributaries, in the vicinity of a mining area as well as through original research on the content of platinum metals from soil and vegetation samples taken from the vicinity of high-traffic roads. Also, a study was carried out to determine the metal content of medicinal plants (Salvia Officinalis and Ocimum Basilicum) grown on artificially polluted soils to observe the accumulation of metals in different parts of plants over time. In this doctoral thesis, 5 original methods for determining platinum metals and metals that can generate hydrides from environmental samples based on ICP-OES and HG-ICP-OES technique have been elaborated, and these methods have been optimized.