Contamination of soils with heavy metals leads to reduction of soil fertility, destruction of natural ecosystems and detrimental effects on the health of society by increasing content of metals in the food chains from microorganisms to plants, animals and humans. Bioremediation is one of the most promising and cost-effective methods of cleaning soils polluted with toxic metals. According to current researchers, microorganisms and plants have the genetic potential to remove toxic metals from contaminated sites. The method of thermodynamic prediction was used to theoretically substantiate the mechanisms of interaction of soil microorganisms and plants with heavy metals. According to the our prediction, exometabolite chelators of anaerobic microorganisms may increase the mobility of metals and thereby contribute to the active transport of metals and their accumulation in plants. Plants of Nicotiana tabacum L. of Djubek cultivar were used as plant material for the current investigation. The examined toxicants were heavy metals, namely cobalt (II), nickel (II), chromium (VI), copper (II) and cadmium (II). The aqueous solutions of metal salts were added to the boxes after two months of plants growing to the final super-high concentration – 500 mg/kg of absolutely dry weight of soil. Quantitative assessments of copper and chromium-resistant microorganisms were made by cultivation on agar nutrient medium NA with a gradient of Cu(II) and Cr(VI). The concentration of metals in soil and plant material (leaves, stems and roots) was determined by atomic absorption method. The study revealed that heavy metals inhibited the growth of the examined tobacco plants. This was expressed by the necrosis of plant tissues and, ultimately, their complete death. Despite this, all investigated heavy metals were accumulated in plant tissues during 3–7 days before death of plants. The uptake of metals was observed in all parts of plants – leaves, stems and roots. The highest concentrations of Co(II), Ni(II), Cd(II), Cr(VI) were found in the leaves, Cu(II) – in the roots. The results show that the bioremoval efficiency of the investigated metals ranged 0.60–3.65%. Given the super-high initial concentration of each of the metals (500 mg/kg), the determined removal efficiency was also high. Cadmium was the most toxic to plants. Thus, the basic points of the thermodynamic prognosis of the possibility of accumulation of heavy metals by phytomicrobial consortium were experimentally confirmed on the example of N. tabacum plants and metal-resistant microorganisms. The study demonstrated that despite the high initial metals concentration, rate of damage and death of plants, metals are accumulated inplant tissues in extremely hight concentrations. Soil microorganisms were observed to have high adaptation potencial to Cu(II) and Cr(VI). In anaerobic conditions, microorganisms presumably mobilize heavy metals, which later are absorbed by plants. The obtained results are the basis for the development of environmental biotechnologies for cleaning contaminated soils from heavy metal compounds.

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The paper is devoted to spatial distribution of low-frequency magnetic susceptibility (χ) of surface sediments in Chernivtsi city as an informative indicator of geochemical contamination of the topsoil. The bulk content of heavy metals in urban soils and the correlations between the χ, frequency dependence of magnetic susceptibility (kfd) and the content of Cd, Mn, Cu, Ni, Pb, Zn were studied. Χ vary from 10∙10-8 to 1286∙10-8 m3/kg with a median value of 66∙10-8 m3/kg. In 20 % of samples χ exceeds the median value three times or more, indicating that the soil is contaminated with iron dust and magnetic particulate matter derived from anthropogenic aerosols. Priority contaminants of city soils are metals such as Pb and Zn, the bulk content of which exceeds the trigger concentration in the vast majority of samples. The χ revealed strong correlation with bulk content of Pb and Zn and the weaker one, but still statistically significant, with Cu and Cd. An additional criterion for the common anthropogenic origin of heavy metals and magnetic minerals in soils is the significant negative correlation coefficients between kfd and content of Zn, Pb, and Cu. So, it can be argued that the increase in Zn, Pb, and Cu content is accompanied by an increase in concentration of magnetic minerals in the multidomain state. The maps were produced, showing spatial distribution of χ and Pollution Load Index (PLI), calculated by three metals (Zn, Pb, and Cu). For 51 % of the samples, the PLI indicates no contamination, 35 % indicate moderate contamination,14 % are strongly contaminated. These results prove that surface sediment over a large area of the city require measures to reduce their toxicity. The correlation coefficient between χ and PLI makes 0.88, indicating χ as a quick indicator of geochemical soil contamination in the city of Chernivtsi.

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