Typomorphic characteristic of gold from tailings of pyrite-polymetallic deposits of Siberian

The long-term stored tailings of the ore concentration of pyrite-polymetallic ore deposits are an ideal natural laboratory in which it is possible to study the gold transformation from primary ores to supergene with superimposed anthropogenic characteristics. The typomorphic characteristics of native gold are studied on the example of technogenic-mineral formations (TMF) of the Novo-Ursk, Belokluch and Zmeinogorsk deposits (Western Siberia). The grain size distribution of gold and its concentration, morphology, internal structure and chemical composition shows the features of gold conversion in the processes of dissolution, migration and secondary deposition at geochemical barriers. As a result of a typomorphic analysis, external and internal signs were identified that prove that gold underwent supergene transformations directly in the body of the technogenic tailings. The growths and accumulations of nano- and micro-size gold, the formation of particles of aggregate structure, lamination, fine particles and veinlets, openwork edges, as well as the absence of physical damage on the surface of the golds, confirm the active mobility of gold at the scales of tailings and emphasize the complex nature of multi-stage processes of gold mobilization. The gold formation of different chemical composition in TMF is explained by specific physical and chemical conditions for the section of the mound of stored waste, different sources of primary gold and geochemical barriers. Au(S2O3)n(1-2n) and Au(HS)2– are the main complexes responsible for the mobility of gold. Gold of low and medium fineness is formed from thiosulfate complexes, whereas high-fineness gold is formed from hydrosulfide complexes.

WITH REGARD TO THE QUESTION ABOUT THE USE OF ARTIFICIAL BARRIERS IN AREAS WITH MAN-MADE INFLUENCE

One of the ways to improve the environmental situation in various regions of the world has become the improvement of technologies for protection against hazardous pollution in soil, atmosphere, groundwater. The article is devoted to the analysis of the conceptual proposal within the framework of participation in the competition “Students reinventing cities. The promising methods of elimination and localization of environmental pollution using geochemical barriers are outlined. Examples of natural and artificial geochemical barriers are considered. Attention is drawn to the possibility of using anti-filtration screens as artificial barriers in areas with passive technogenic impact. The potential of using artificial barriers for the safe cultivation of plant crops at the former Payatas controlled waste disposal facility in Quezon City, Philippines is being identified. The importance of creating green spaces in the territory with limited opportunities for economic use is justified.

CREATION OF SORPTION FILTER BARRIERS IN RELATION TO STRONTIUM AND ANTIMONY ON THE BASIS OF BRUCITE-CONTAINING ROCKS

In recent years, due to the growth of industry and the urbanization of territories, substances that are relatively rare in the earth's crust are actively included in the cycle of substances, and as a result, they accumulate in significant quantities in the hypergenesis zone. Accordingly, at the moment, the issue of developing recipes and methods for creating geochemical barriers to such substances is very acute.It is known that brucite-containing soils have an increased absorption capacity for heavy metals. Based on this, the authors conducted a number of experiments on the dynamic and static sorption of brucite-containing soils in relation to strontium and antimony. Experiments have shown that such soils can be recommended as sorption filter barriers in relation to the studied metals.

Role of geochemical barriers in forming sulfide ores in various geological environments

Based on long-term studies of cupriferous sandstone and shale deposits, as well as deepsea sulfide ores, various types of geochemical barriers where sulfides form are shown. Cupriferous sandstones and shales form as metals precipitate from redbed reservoir waters on H2S geochemical barrier. Syngenetic and epigenetic barrier types are identified. Oceanic sulfide ores from the Central Atlantic region were studied; as a result, a new hydrothermal-metasomatic sediment-hosted mineralization type was found, along with previously known sulfide ore types (massive ores on the seafloor and stockwork ores in substrate rocks). Geochemical seafloor sulfide formation environments and those in biogenic carbonate bottom sediments are examined.

CHANGES IN THE VANADIUM MIGRATION FORMS ON GEOCHEMICAL BARRIERS IN THE RIVER-SEA MIXING ZONES

The article is devoted to the study of vanadium, a metal capable of stimulating the growth of phytoplankton in situ and has the greatest biological activity in dissolved form. The pattern of an increase in the concentration of vanadium dissolved forms in the mixing zones during the transition from river waters to seawaters is known. In this article, we examine the behavior, ratio and change in the concentrations of vanadium dissolved and suspended forms during the passage of geochemical barriers. The estuarine zone of the Razdolnaya River–Amur Bay (Sea of Japan) is considered as "river-sea" mixing zone. Modelling of physicochemical processes was carried out using the Selector-S and MINTEQA2/PRODEFA2 software systems. Ion-associative models of sea and river water were built and the modelling of the process of their mixing was carried out using the Selector-S software package. The sorption process was simulated using the MINTEQA2/PRODEFA2 software package. The results of modelling physicochemical processes occurring at geochemical barriers help to understand the reasons for changes in concentrations, both total vanadium and biologically active dissolved vanadium forms, during the passage of geochemical barriers in the "river-sea" mixing zones. The results showed that there is a change in the dissolved forms of vanadium migration, their transformation and an increase in the concentration of dissolved forms of vanadium at the geochemical barrier

Fractionation of polycyclic aromatic hydrocarbons at geochemical barriers

The purpose of the study was to identify patterns of fractionation at geochemical barriers (GCB) of associations of marker compounds - polycyclic aromatic hydrocarbons (PAHs). Based on thermodynamic parameters, the throughput of GCB in geochemical systems (GCS) in relation to organic substances at the molecular level is analyzed. PAHs are very informative indicators of the properties of GCB (up to singular surfaces). The processes of migration and selective penetration through GCB of 15 PAHs from the list of priority pollutants recommended by the US Environmental Protection Agency (widely used in the world EPA list): Naphthalene (Naph), acenaphthene (Ace), Fluorene (Flourene), Phenanthrene (Phen), Anthracene (An), Fluoranthene (Flu), Pyrene (Py), Benzo(a)Anthracene (BaA), Chrysene (Chr), Benzo(b)Fluoranthene (BbFlu), Benzo(k)fluoranthhene (BkFlu), Benzo(a)pyrene (BaP), benzo(ghi)perylene (Bghi), Dibenzo(a, h) anthracene (DbA), Indeno(1,2-cd)pyrene (Ip). Being geochemical markers, these compounds can accumulate on barriers and selectively penetrate through them, making them especially important objects of study. Despite numerous studies, these mechanisms of mass transfer have not been sufficiently studied. The types of GCB have been identified in terms of their permeability to PAHs. It is shown that the functions of GCB in systems are much more significant and consist not only in the separation of systems from the external environment and the regulation of mass transfer. The above models of migration and accumulation are based on quantitative estimates, which makes the results more reasonable in comparison with the “conceptual” representations of the behavior of substances on GCB in most studies. The most important point - the influence of the medium contact time for establishing a stable state (stability by the migration of compounds) on GCB has been demonstrated.

Geochemical conditions of natural wetland and paddy fields in the Poyang Lake area, China

During the last several decades, wetlands are losing their ecological functions due to increasing anthropogenic loads. One of these functions is the ability to bind elements forming geochemical barriers. The research aimed to study the geochemical conditions of natural wetlands and flooded paddy fields (artificial wetlands) in the Ganjiang River basin to trace geochemical barriers. The research approach was based on a comprehensive analysis of water and aqueous extracts from bottom sediments and paddy soils, including chemical and mineral composition. The samples were collected in November 2019, during the dry season at the end of harvesting. Chemical analysis was performed using standard methods for natural substances: titrimetry, photometry, ionic chromatography, high-temperature oxidation, ICP-MS, and ICP-AES. The mineral composition of the soils and sediments was determined by XRD. It was found that the main physicochemical characteristics (TDS, pH, main component concentrations) of the natural wetland water correspond to the surface water of the study area, whereas the irrigation water is similar to shallow groundwater. The content of trace elements in the irrigation water is higher than in the natural wetland water. Generally, the trace element composition of the natural wetland water corresponds to the geochemical background of the study area. Analysis of the mineral and chemical composition of the paddy soils and sediments indicates the geochemical barriers that accumulate a wide range of elements. In the natural wetland, the geochemical barrier is likely associated with a decrease in oxygen content and advective transport rate in the sediments, whereas in the paddy fields, the precipitation of clay minerals in the soil profile forms the geochemical barrier related to a decrease in filtration properties and advection–diffusion transport. Graphic abstract

Monitoring of the Migratory Ability of Heavy Metals in the Soil-Plant System

The profile migration of pollutants that occurs most intensively in spring, autumn, and summer with a large amount of precipitation when intensive descending flows of soil moisture take place is of particular importance. The migration of heavy metals is limited by their deposition on geochemical barriers. The study of the profile migration and accumulation of heavy metals showed that metals have an unequal behavior in soils; a change in their content in the profile is noted. The article presents the dynamics of the distribution of moving forms of heavy metals in different soils of the Orenburg region. An equation of exponential regression was proposed. The equation allows assessing the migrative ability of heavy metal by the value of indicator α. There were studied physical and chemical characteristics of the soil, namely its composition, the content of heavy metals, which in total affects the overall state of the soil and plant system. The structure of the system was analyzed and determined by probabilities of the presence of a pollutant in the components of the system. As a result, a complex indicator showing the movement of heavy metals in the soil-plant system was calculated.