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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.

Nowadays, nanotechnology is one of the most dynamically developing and most promising technologies. However, the safety issues of using metal nanoparticles, their environmental impact on soil and plants are poorly understood. These studies are especially important in terms of copper-based nanomaterials because they are widely used in agriculture. Concerning that, it is important to study the mechanism behind the mode of CuO nanoparticles action at the ultrastructural intracellular level. It is established that the contamination with CuO has had a negative influence on the development of spring barley. A greater toxic effect has been exerted by the introduction of CuO nanoparticles as compared to the macrodispersed form. A comparative analysis of the toxic effects of copper oxides and nano-oxides on plants has shown changes in the tissue and intracellular levels in the barley roots. However, qualitative changes in plant leaves have not practically been observed. In general, conclusions can be made that copper oxide in nano-dispersed form penetrates better from the soil into the plant and can accumulate in large quantities in it.

Potentially toxic elements (PTE) pollution has a pronounced negative effect on the soil and its components. The characteristics of soil organic matter and the activity of soil enzymes can serve as sensitive indicators of the degree of changes occurring in the soil. This study aims to assess the effect of long-term severe soil contamination with Zn and Cu on water-soluble organic matter (WSOM) and the associated changes in the biochemical activity of microorganisms. The total content of Zn and Cu in the studied soils varies greatly: Zn from 118 to 65,311 mg/kg, Cu from 52 to 437 mg/kg. The content of WSOM was determined using cold and hot extraction. It was revealed that the WSOM, extracted with cold water is a sensitive indicator reflecting the nature of the interaction of Zn and Cu with it. With an increase in the Cu and Zn content, the amount of WSOM extracted with cold water increases due to rise in the complex-bound metal compounds associated with it. The content of complex-bound compounds Zn in Spolic Technosols reaches 50% of the total metal content. It is shown that one of the biogeochemical mechanisms of microorganisms' adaptation to metal contamination is clearly manifested by the increase in the content of WSOM. The precipitation of metal carbonates develops in the soil which reduces the mobility and toxicity of PTE. Due to this mechanism, a decrease in the activity of dehydrogenases and urease was not prominent in all studied soils, despite the very high level of pollution and the transformation of organic matter. The study of the relationship of PTE with the most easily transformed part of WSOM and the activity of soil enzymes is of great importance for an objective assessment of possible environmental risks., (Copyright © 2020 Elsevier Inc. All rights reserved.)

The aim of this work was to study the effect of the attendant anions and particle-size distribution on the adsorption of copper by chernozems of Rostov region (Russia). The samples of soil in the natural cationic form were treated with solutions of copper nitrates, acetates, chlorides, and sulfates at a soil: solution ratio of 1:10. The concentrations of the initial copper solutions varied in the range from 0.05 to 1 mM/L. The suspensions were shaken for 1 h, left to settle for a further 24 h and then filtered. The metal concentrations in the filtrates were determined by atomic absorption spectrometry. The concentrations of the adsorbed copper cations were calculated from the difference between the metal concentrations in the initial and equilibrium solutions. The effect of the attendant anions Cl − , SO 4 2 − , Ac − , and NO 3 − and particle size distribution on the adsorption of copper by chernozems of the Rostov region has been studied under laboratory conditions. The shape of the adsorption isotherms varies depending on the attendant anion and is described by the Henry, Freundlich, and Langmuir equations. The adsorption of copper by the soil is accompanied by the acidification of equilibrium solutions ( рН eq ): 0.53 ≤ ΔрН eq ≤ 2.06, which depends on the attendant anion. The highest value of ΔpH eq corresponds to the adsorption of Cu 2 + from the copper sulfate solution and its lowest value, from the copper chloride solution. The effect of the attendant anions decreases in the series: Cu(Ac) 2 > CuCl 2 > Cu(NO 3 ) 2 > > CuSO 4 . In the southern chernozems, a close correlation is observed between the maximum copper adsorption and the content of clay and silt ( R = 0.99). No correlation is found between the values of adsorption constants and particle size distribution, which is related to the changes in the chemistry and mineralogy of the soils studied. [ABSTRACT FROM AUTHOR]