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Phytoremediation is a promising method for the removal of toxic trace elements, specifically of copper, from the contaminated soil in the mining regions of Armenia. Thereby, the objectives of our study were the assessment of copper accumulation capacity and phytoremediation suitability of wormwood (Artemisia absinthium L.), a potential metal hyperaccumulator, as well as the identification of the influence of some chelating agents and their combinations on copper phytoremediation effectiveness. The results of studies have shown that A. absinthium is a relatively well-adapted plant species with the ability to grow in copper-contaminated soils collected from the surroundings of Zangezur Copper and Molybdenum Combine (south-east of Armenia). The observed decrease in plant growth in contaminated soil was possible to restore by the use of ammonium nitrate. It was revealed that for the remediation of copper-contaminated soils by phytostabilisation method, A. absinthium could be grown without the application of chelating agents, as being a perennial herb, it is able to accumulate relatively high contents of copper in its root and do not transfer this metal to the above-ground part at the same time. As opposed to the phytostabilisation method, for the cleaning of copper-contaminated soils through phytoextraction method by A. absinthium, the application of chemical amendments is needed for the enhancement of copper bioavailability and for its intensive transportation to the above-ground part of the plant. Collating the effects of various chemical agents on the plant, we concluded that the growth scheme, when the application of NH 4 NO 3 , a promoter of plant growth, is combined with the joint use of citric and malic acids, can be applied as the most expedient approach for remediation of copper-contaminated soils by phytoextraction method., (© 2021. The Author(s), under exclusive licence to Springer Nature B.V.)

Modeling metal sorption in soils is of great importance to predict the fate of heavy metals and to assess the actual risk driven from pollution. The present study focuses on adsorption of HM ions on two types of hydromorphic soils, including calcaric fluvisols loamic and calcaric fluvic arenosols. The individual and competitive adsorption behaviors of Cu and Zn on soils and soil constituents are evaluated comprehensively. It is established that the sorption processes were best described with the Langmuir model. The results suggest that the calcaric fluvic arenosols are more vulnerable to heavy metal input compared to fluvisols loamic. In all cases, Cu had a higher range of values of the adsorption process parameters relative to Zn. The Zn is likely to be the most critical environmental factor in such soils since it exhibited a decreased sorption under competitive conditions. The retention mechanisms of HM in hydromorphic soils are considered. Based on theoretical calculations of ion activity in soil solutions using solubility diagrams of Cu and Zn compounds, the possibility of precipitation of Cu hydroxide and Zn carbonate in the studied soils is shown. Direct physical methods of nondestructive testing (XAFS and XRD) are applied to experimentally prove the formation of these HM compounds on the surface of montmorillonite, the dominant mineral in hydromorphic soils, and calcite. Thus, the combination of both physicochemical methods and direct physical methods can provide a large amount of real information about the mechanisms of HM retain with solid phases., (© 2020. Springer Nature B.V.)

Metal speciation, linked directly to bioaccessibility and lability, is a key to be considered when assessing associated human and environmental health risks originated from anthropogenic activities. To identify the Zn and Cu speciation in the highly contaminated, technogenically transformed soils (Technosol) from the impact zone near the industrial sludge reservoirs of chemical plant (Siverskyi Donets River floodplain, southern Russia), the validity of the BCR sequential extraction procedure using the X-ray absorption fine-structure and X-ray powder diffraction (XRD) analyses was examined after each of the three stages. After the removal of exchange and carbonate-bonded Zn and Cu compounds from Technosol (first stage of extraction), the resulting residual soil showed enrichment in a great diversity of metal compounds, primarily with Me-S and Me-O bonds. The number of compounds with a higher solubility decreased at the subsequent stages of extraction. In the residual soil left over after extracting the first and second fractions, the dominant Zn-S bond appeared as würtzite (hexagonal ZnS) that made up more than 50%, while the Cu-S bond was almost completely represented only by chalcocite (Cu 2 S). The XRD analysis revealed the authigenic minerals of metals with S: sphalerite (cubic ZnS), würtzite (hexagonal ZnS), covellite (CuS) and bornite (Cu 5 FeS 4 ). The scanning electron microscopy data confirmed that würtzite was the dominant form of Me with sulfur-containing and carbonate-containing minerals. The Zn-S bond was the main component (57%), whereas the Cu-O bond was dominant in the residual fraction (the fraction after the third-stage extraction). The results revealed that the composition of the residual fractions might include some of the most stable and hard-to-recover metal compounds of technogenic origin. Thus, the application of the novel instrumental methods, coupled with the chemical fractionation, revealed the incomplete selectivity of the extractants in the extraction of Zn and Cu in long-term highly contaminated soils.

The results of biogeochemical and bioindication studies on the resistance of natural populations of macrophyte plant-cattail (Typha australis Schum. & Thonn) on the coast of the Taganrog Bay of the Sea of Azov and the sea edge of the Don River delta with regard to local pollution zones are presented. Plant resistance has been assessed through manifestation of their protective functions in relation to heavy metals. An excess in the lithospheric Clarkes and MPC in Zn, Cd and Pb in Fluvisols has been found. The total index of soil pollution (Z c ) has made it possible to identify areas with different categories of contamination within the study area exposed to human impact. High mobility of Zn, Cd, Pb, Cr and Ni in Fluvisols has been revealed, which is confirmed by the significant bioavailability of Zn, Cr and Cd that are accumulated in the macrophyte plant tissues. The absorption of heavy metals by cattail plants is allowed for both the soil and the water of the nearby reservoir, where aquatic systems are a kind of "biological filter" contributing to water purification from pollutants. The impact of the environmental stress factor has been found to be manifested not only in the features of heavy metal accumulation and distribution in plant tissues, but also at the morphological and anatomical level according to the type of prolification. Changes in the cell membranes as well as in main cytoplasmic organelles (mitochondria, plastids, pyroxis, etc.) of the root and leaf cells have been identified, the most significant changes in the ultrastructure being noted in the tissues of leaf chlorenchyma. It is assumed that the identified structural changes contribute to slowing down of the ontogenetic development of plants and reduction in their morphometric parameters when exposed to anthropogenic pollution. Therefore, cattails can be effectively used as biological indicators while determining environmental pressures.