Geochemical Barriers Research Articles

Содержание валовых форм цинка, свинца и кадмия в дерново-подзолистых супесчаных почвах земель сельскохозяйственного назначения

Abstract. Purpose and objectives. The research is aimed at studying the peculiarities of the distribution of gross forms of zinc, mumps, cadmium according to the soil profile of sod-podzolic sandy loam soils of agricultural lands of the Ryazan region and determining the current regional background. Methodology and methods. To solve the tasks set, pits with a depth of 1.5 m were laid in different regions of the region, the depth and structural features of the soil layer and the effect on the migration conditions of the studied elements were analyzed. Based on the results of determining the content of the studied elements in the soil at intervals of 0.1–0.2 m to the maternal, the calculation of background concentrations was performed. A comparative analysis of the proposed background values with well-known values of world and domestic researchers has been carried out. The scientific novelty of the conducted research lies in the fact that the proposed background values are modern and calculated directly for the sod-podzolic sandy loam soil of the Ryazan region. Results. The structure of soil profiles of sod-podzolic sandy loam soil at a depth of 110–120 cm has the following form: O – A – EL – ELBt – Bt – BtC – C. At the same time, noticeable geochemical barriers delaying the migration of heavy metals are noted in the horizon A and Bt. The obtained values of the studied elements were in the concentration ranges for Zn (5.4–12.8 mg/kg), Pb (2.1–7.4 mg/kg), Cd (0.031-0.081 mg/kg). Background concentrations are proposed: Zn – 8.3 mg/kg, Pb – 4.2 mg/kg, Cd – 0.053 mg/kg, which differ from the well-known values of world and domestic researchers presented in a comparative analysis and give a modern idea of the regional background content of gross forms of zinc, lead and cadmium in sod-podzolic sandy loam soils Ryazan region.

Geochemical Features of Organo-Accumulative Soils of Subtaiga and Subtaiga-Forest-Steppe Light Coniferous Forests of Northern Mongolia

Geochemical features of organo-accumulative (Eutric Regosols (Laomic, Ochric), Cambic Someric Phaeozems (Loamic)) soils widely distributed in the soil cover of the subtaiga and subtaiga-forest-steppe light coniferous forests forming the lower boundary of the forest belt in the mountain structures of Northern Mongolia are considered. Data on the microelement composition of soil-forming rocks are given. It was found that the paragenetic association of trace elements in them is represented by Pb, Cu, Zn, Co, V, Cr, Ni, Mn, Mo, Ba, Sr, Zr and B. It was found that, compared with the average content in the lithosphere within the subtaiga and subtaiga-forest-steppe forest-growing belt, the residual and re-deposited weathering crusts of igneous rocks are enriched with Zn, Cr, Mo, B, at the same time they contain less Pb, Co, Mn, Ba, Sr, Zr. The residual and re-deposited weathering crusts of carbonate rocks are enriched with Pb, Cu, Zn, V, Cr, Sr, B, they contain little Co, Ni, Mn, Mo, Ba, Zr. Data on the morphological structure of soils, their physico-chemical and chemical properties, as well as on the content of trace elements and their radial distribution in the soils under consideration are discussed. The data obtained indicate the accumulation of most trace elements in the surface organogenic and humus-accumulative horizons of soils, which is associated with both the heterogeneity of soil-forming rocks and the influence of soil processes that cause the accumulative redistribution of elements and their deposition on organo-sorption and carbonate geochemical barriers. It is shown that the studied soils differ not only in the absolute values of trace elements involved in the biological cycle, but also in the intensity of their involvement in biogenic migration.

Arsenic accumulation in spolic technosols in the area of a large copper smelting plant in the Middle Urals

Relevance. The necessity to study arsenic behaviour in soils as one of the main pollutants of depositing environments in areas of mining and metallurgical industry. In recent decades, arsenic emissions into the environment have reached a huge scale, so this element attracts the attention of researchers around the world. But in spite of all the studies of this problem, there are still some aspects that need to be clarified to understand the geochemistry of arsenic. This paper deals with spolic technosols with critically high arsenic content in the soil profile with alternating water-logged and dry conditions. As one of the main soil-forming elements, orthosteins contain significant amounts of iron and manganese compounds and are capable of adsorption and involvement of the elements in nodule formation. Aim. To determine the influence of orthosteins on arsenic accumulation in soil subjected to intensive anthropogenic load. Object. Ortsteins spolic technosols in the zone of operation of copper smelting plant and background soils not exposed to pollution. Methods. Arsenic was determined by inversion voltammetry method. Morphological characterisation and patterning of the orthosteins were performed by scanning electron microscopy using a Thermo Fisher Phenom XL G2 Desktop SEM unit. Results. The study of morphological features of orthosteins revealed differences in soils subjected to greater anthropogenic load. Arsenic was not detected inside the orthosteins in all studied soils. Also arsenic concentrations in the total mass of ortstein is up to 40–50% of the soil mass. This fact indicates the accumulation of arsenic by surface adsorption and the appearance of orthosteins as a geochemical barrier. The data obtained in the course of this work can contribute to the search for ways to clean up soils contaminated with arsenic, as well as provide an understanding of the basic processes of the behaviour of this element in soil formation.

Fluid inclusions in quartz of the gold-ore occurrences and gold-quartz intergrowths from placers in the Sololi uplift of the Olenyok arch (Yakutia)

Fluid inclusions have been studied in vein quartz with gold sulfide mineralization from metamorphosed sandstones of the Eekite series and metarhyolites of the Early Proterozoic, in quartz breccia from the zone of overlapping gold mineralization on the Early and Middle Permian sandstones, as well as in the gold quartz intergrowths from the Sololi River placer. It has been revealed that formation of quartz breccias occurred within a wide temperature interval from 230 to 425 ºC, with predominance of carbon dioxide and nitrogen in the vapor phase. It is suggested that the increased nitrogen content may be associated with a chemical reaction between the fluid and ammonium-containing silicates of host rocks, in which nitrogen in the form of NH4+ isomorphically replaces potassium at the regressive stage of metamorphism. At the same time, it is possible that mantle nitrogen, which was transported along the Anabar-Eekite deep fault, participated in formation of the studied breccias. The close homogenization temperatures and similar nature of the water-salt composition for the fluid inclusions of quartz veins that inject the Eekite series meta-rocks and meta-rhyolites indicate the synchronism of their formation and attribute them to the common stage of ore formation. Quartz veins with gold sulfide mineralization were the primary sources of pebbles with gold-quartz intergrowths from the Sololi River, this is evidenced by similarity of principal characteristics of fluid inclusions. Oxidizing conditions of the mineralization serve as favorable factor for the Au deposition, it is indicated by the predominant CO2 content in fluid inclusions, keeping role of a geochemical barrier and leading to an elevated gold content in quartz veins.

Porewater exchange and iron transformation in a coastal groundwater system: a field investigation, driving mechanisms analysis, and conceptual model

The high concentration of dissolved iron (Fe) in coastal waters triggers Lyngbya blooms in the Moreton Bay region of Southeast Queensland, Australia. Previous studies have provided a restricted understanding of how land-derived Fe is transported and then transformed into other forms (e.g., Fe oxides) before its release into the ocean. Here, a field investigation was conducted at a sandy beach on the northern end of Deception Bay, Queensland, Australia, focusing on porewater exchange and Fe transformation. This study revealed that tides provided a significant mechanism for driving the groundwater-seawater mixing in the intertidal area. Such forcing formed an upper saline plume (USP) with high dissolved oxygen (DO), creating a dynamic reaction zone for Fe oxidation and precipitation beneath the USP. The spatial distribution of Fe oxides highlighted a substantial Fe content in the subsurface, providing concrete evidence for the transformation of Fe from an aqueous state to a solid form. It also exhibited a low-permeable area that served as a geochemical barrier, absorbing chemical components like phosphate. These findings can assist in constructing a more accurate transport model that couples physical and geochemical processes to quantify the mechanisms driving Fe transformation in coastal areas and further deepen our comprehension of the hydrogeochemical functionalities in land-ocean connectivity via groundwater.

Mineralogy, fluid regime and potential ore content of the post-accretion Ivdel gabbrodolerite-monzonite-granodiorite complex (Northern Urals)

Research subject. Hypabyssal intrusive bodies of a gabbro-dolerite-monzonite-granodiorite composition, common among the Devonian island-arc sequences of the East Tagil structural-formational zone in the Northern Urals. These bodies are dated as the Late Devonian-Early Carboniferous and attributed to the post-accretionary continuously differentiated Ivdel complex. Material and methods. The composition of rock-forming and accessory minerals of these intrusive bodies was studied using an SX-100 microanalyzer. This made it possible to obtain new data on the conditions of their formation, features of the fluid regime, and potential ore content. In addition, the geodynamic setting of this period was clarified, along with the composition, possible position of the primary mantle source, and the features of its fluid regime. Results. It was established that the mafic rocks (dolerites) in the Ivdel complex correspond to derivatives of the depleted mantle, with a primary source close to N-MORB basalts. The connection between the source and the separation of the slab and the “mantle window” located under the frontal zone of the former East Tagil island arc was substantiated. Such a position of the melting chamber determines the primary weak water saturation of dolerite magmas and their redox regime. According to mineralogical data, this feature is further manifested in the formation of the entire series of rocks of the Ivdel complex (with an increase in the iron index of clinopyroxenes and amphiboles, an increase in titanium contents in titanomagnetite, and other data). Further evolution of magmas (from dolerites to monzonites, quartz diorites, and granodiorites) occurred as they moved upward to the Earth’s surface and reflected the increasing contamination of differentiated melts by suprasubduction island-arc matter. Another important petrological feature of this complex is its formation with the participation of a chlorine-rich magmatogenic fluid. Depending on the composition of intruding melts, their contents of water, chlorine and oxygen activity, a number of autonomous degassing fluid-magmatic systems are formed. These systems are characterized by noticeable features in the processes of post-magmatic autometasomatosis, with the participation of an iron-chloride fluid. According to the regime of volatiles (halogens, water, and oxygen), the common affiliation of such autonomous fluid-magmatic systems to titanomagnetite ferrofacies (according to G.B. Fershtater), determines both their general metallogenic specialization and potential ore content. The removal of volatiles from such fluid-magmatic systems could be accompanied by extraction and transfer of chlorophyll ore elements from crystallizing melts to exocontacts of intrusive bodies. This, in the presence of migration zones favorable for fluids (faults, crushing zones, etc.) and geochemical barriers (especially in the presence of favorable enclosing sulfide-bearing island-arc strata), could have contributed to the formation of hydrothermal-metasomatic ore mineralization (Cu, Zn, Au, Mo and etc.). Such ore-bearing zones during erosion could be the primary source of gold for the known placers of this region. Large bodies of gabbrodolerites of the Ivdel complex may be promising for high-Ti magnetite-ilmenite mineralization.

An original set of nanometer-scale mineralogical analyses of cookeite and the implications for Li enrichment: No. 21 coal, Mengjin Mine, western Henan

Critical elements in coal deposits, such as lithium (Li), have attracted attention recently due to their economic value. Many studies have suggested that the high enrichment of Li in coals is predominantly associated with cookeite, a Li–bearing chlorite mineral of hydrothermal origin. However, the identification of cookeite in coal has primarily relied on indirect methods, owing to the low atomic number of Li, which presents significant challenges for precise observation. The Shanxi Formation No. 21 coal in North China is enriched in Li. This study established a nanometer–scale mineralogical analytical technique (including high–resolution transmission electron microscopy (HR–TEM), fast Fourier transformation (FFT), and standard mineral simulation single-crystal diffraction (SSCD)) for the identification of the cookeite and evaluated the Li enrichment mechanism and recovery in this coal (low–volatile bituminous to semi–anthracite) based on a model for the Li mineralization. The Li content of the No. 21 coal ranges from 25.2 to 203 ppm. The Li content shows a strong correlation with the ash yield, Al2O3, SiO2, and detrital elements, indicating a dominant aluminosilicate affinity and detrital origin. The major aluminosilicate minerals in coal are kaolinite, chlorite, and illite. The geochemical indicators (the Al2O3/TiO2 ratio and its relationships with the Zr/TiO2, Nb/Y, and Nb/Yb ratios) indicate that the sediment sources are determined to be intermediate–felsic igneous rocks, probably the Mesoproterozoic moyite (a type of K– feldspar granite) in the Yinshan Oldland. Additionally, the coal can be divided vertically into three sections (Sections I, II, and III), corresponding to three stages of peat formation. Overall, from Section I to Section III, the degree of detrital input increased, and the groundwater and marine influences strengthened and weakened, respectively. Section II exhibits anomalous Li enrichment mainly associated with reducing environments and the geochemical barrier caused by the interaction between infiltrating seawater and groundwater. The detrital kaolinite assemblage with authigenic minerals such as secondary REE–rich minerals (bastnasite), chamosite, and quartz, as well as the REY enrichment patterns, suggests that the No. 21 coals, mainly Section II, may have existed the hydrothermal alteration. Cookeite is identified primarily in Section II and coexists with kaolinite based on TEM observations, suggesting that the cookeite is of hydrothermal origin and formed from pre–existing Li–rich kaolinite. Most samples from Section II meet the mining grade of Be–Li–Nb–Ta ore deposits (Li2O > 0.2%). Thus, this study offers valuable insights into the extraction and recovery of Li from coal combustion residues, particularly when cookeite is the primary Li–bearing mineral.

Preventive geochemical barriers during transport construction

The article discusses the possibility of using chlorite crushed stone as part of geochemical barriers in transport construction. It has been shown that during the construction of railways and during their operation, the main pollutants are petroleum products and heavy metal ions. To substantiate and study the neutralizing properties of chlorite crushed stone, infrared spectroscopy, ionomer, atomic absorption spectrometry and the gravimetric method for determining petroleum products were used. Research has shown that chlorite crushed stone is a quartz-albite-chlorite shale with a small inclusion of carbon; its physical and mechanical characteristics are not inferior to granite crushed stone. The oil capacity of chlorite crushed stone depends on the concentration of petroleum products in the model solution and ranges from 0.03 to 0.5 g/g. Chlorite crushed stone has a capacity towards nickel, iron and cadmium ions, while their simultaneous presence in the model solution does not have selectivity towards these ions. It has been proven that when the capacity of chlorite crushed stone is fully realized in relation to one of the heavy metal ions, it is not washed out and replaced by another metal ion (for example, nickel and iron ions). It has been proven that the presence of organic contaminants in the model solution does not significantly affect the capacity of chlorite crushed stone for heavy metal ions. It has been shown that chlorite crushed stone, due to its physical, physical-mechanical and chemical properties, can be used in geochemical barriers to protect the environment from pollution.

Analysis of nickel distribution in soil profiles of sod-podzolic types

The research is aimed at studying the peculiarities of distribution of gross nickel in genetic horizons of soil profile of sod- podzolic sandy loamy and sandy soils of agricultural land in the Ryazan region and determining the current background concentration. To solve the set objectives were laid 10 pits up to 150 cm deep in Kasimovsky, Ermishinsky, Shilovsky, Sasovsky, Klepikovsky, Kadomsky districts of the Ryazan region in the period from 2016 to 2023, analyzed the depth and features of the structure of soil layers, the influence on the conditions of nickel migration. According to the results of nickel content determination the calculation of background concentration was performed. The comparative analysis of the proposed modern regional background value with well-known values of global and domestic researchers: approximate background concentrations for the average strip of Russia, hygienic standards characterizing the approximate permissible concentration of the substance in the soil, soils of the world according to the materials of the international geochemical atlas, soils of the world according to A.P. Vinogradov, global, zonal, regional values of the background according to Y.E. Saet, data of other researchers on the Ryazan land. The structure of soil profiles of soil at a depth of 110-130 cm has the following form: O – A - EL - ELBt - Bt - BtC - C. At the same time weakly noticeable geochemical barriers are noted in horizons A and Bt. Values of gross nickel were located in the concentration range of 3.3 - 16.8 mg/kg. A background concentration of 9.5 mg/kg was proposed, which differs from the generally known values presented in the comparative analysis and gives a modern idea of the regional background content of the gross form of nickel.

Техногенная трансформация почв степей европейской части России в условиях углеводородного загрязнения

The object of the study is the soils of the Orenburg region, Buzuluk district, contaminated with pollutants. The aim of the study is to identify patterns of accumulation of heavy metals in southern chernozems that have been subjected to hydrogen pollution and the studied conglomerate by pollutants of the European part of the steppes of Russia. As well as the establishment of a set of factors and confirmation of their influence on the stability of landscapes in conditions of soil degradation and further formation of geochemical barriers formed by pollutants. The materials and methods of research are the literature of leading Russian specialists studying this issue, as well as regulatory and legal documentation: GOST standards, SanPiNs, Resolutions of the Government of the Russian Federation. Cartographic and graphic materials have been built that display sampling points, the content and dependence of elements on pollutants. A field survey (reconnaissance of the area) was conducted in the conditions of eluvial formation of soil and soil-forming accumulation, against the background of changes in the processes of formation of geochemical chains. Soil samples were taken from the site, and a syntaxoid analysis was performed. The total value of the maximum permissible concentrations of pollutants in the soils of the studied area within the boundaries of the administrative region of three oil fields has been determined. According to the results of the study, a pattern of accumulation of heavy metals from the area of the geochemical barrier formed by pollution with petroleum products was revealed. The perspective of the development of the influence of accumulations of pollutants on the transformation of the natural landscape is visualized. In areas contaminated with pollutants, it is necessary to carry out reclamation works: technical and biological stages, in compliance with environmental protection.

Effects of mine water discharge on river sediments: metal fate and behaviour, Upper Silesian Coal Basin

The study aims to characterise the changes in elemental composition in the river sediments of streams influenced by mine waters enriched with radionuclides. The study took place in the vicinity of Ostrava, a city located in a coal mining region in the Czech Republic, namely the Upper Silesian Coal Basin. River sediments and waters of the Karvinský potok and Stružka streams were investigated. Field measurements were made for ambient dose equivalent rate (ADER). Laboratory gamma spectrometry and X-ray fluorescence were used to determine the content of radionuclides and elemental composition in river sediments. Water samples were analysed for the content of major ions and radionuclides. The field ADER measurement proved elevated content of radionuclides with values exceeding 1,000 nSv/h in both streams. The discharged mine waters were Na–Cl type, containing an 226Ra (0.68–0.70 Bq/l) as a dominant radionuclide. Laboratory measurements of radionuclides in bottom sediments proved that the prevailing source of radiation are 226Ra and 232Th in both streams. The calculated enrichment factors showed extreme values for Sr, Cr, Pb, Zn, Cu, and Mo. The precipitation reactions forming Ca-minerals (calcite and aragonite), Fe-bearing minerals (hematite, goethite and amorphous Fe(OH)3) and hausmannite were found to be the primary geochemical process underway in the studied riverine systems. The correlation between elements and radionuclides demonstrated the significant role of geochemical barriers that lead to the precipitation of radionuclides from solution. The results show that the precipitation takes place preferentially in places where other waters enter the stream, or where recent organic matter is present.

Влияние кислых сульфатных вод на загрязнение почв террикона в Карабашском рудном районе

Introduction. Technogenic mineral formations are one of the potential sources of pollutants, including heavy metals. On the territory of the Karabash ore district as a result of copper and cobalt ore mining, waste rock heaps are formed and stored. As a result, under the influence of acidic precipitation, oxidation of the surface part of the spoil heap occurs, and the formed products, among which there are heavy metals, are transported by water and aeolian streams to the adjacent landscapes. Methods and materials of research. In the course of work investigated the spoil heap formed by wastes of the mine «Tsentralnaya» in Karabash, Chelyabinsk region. Sampling from the surface of the spoil heap, as well as soil samples with distance from it. The mineralogical composition was determined in the rocks of the heap by X-ray diffraction with Cu-Kα-radiation and crystal mono chromator. Quantitative content of heavy metals was carried out by X-ray spectral method. The reaction of the medium and carbon content of organic matter, as well as the gross content of mobile and water-soluble forms of heavy metals were determined by inversion voltammetry method. According to the results of quantitative analysis of heavy metals in soils, the coefficient of total pollution - Zc was calculated. Research results and discussion. As a result of laboratory analyses, the lithological composition of the main rocks of the spoil heap was determined, which is represented by the main two types: 1) altered quartz-chlorite-sericite schist; 2) highly transformed rocks with no discernible primary mineral composition. The first type contains mainly quartz, feldspars, mica, chlorite and pyrite. The mineralogical composition of the second group is represented by silicates and alumina silicates with gypsum, hydro-arosite and calcium sulphate. Oxidation and limonitization of spoil heap rocks is going on everywhere. In the chemical composition of spoil heaps, predominant are macro-elements Fe, Ca, Mg, K, Na, P, their concentration ranges from 0.13 to 20.38 %, also present in high concentrations of S 0.27-12.31 %, As 0.007-0.11 % and Zn 0.026-0.087 %. All other elements are less than 0.01 %. As a result of rock oxidation such heavy metals as Zn, Cd, Pb, Cu migrate from dumps in the form of sulphates, which is promoted by lowering the pH of the environment. It is revealed that soils located in the depression, on the way of hydro-genic flows, are geochemical barriers for heavy metals. The gross content of heavy metals in soils varies within high limits. Maximum concentrations were recorded in 0-10 cm layer in organogenic and grey humus horizons:Zn - 2890 mg/kg; Cd - 32 mg/kg; Pb - 1270 mg/kg; Cu - 3060 mg/kg. In the vicinity of the spoil heap, relatively high content of mobile forms of heavy metals was recorded inside the soil profile, in the surface layers of soils, with distance from the spoil heap. With distance from the heap, the share of mobile forms decreases in 2 - 2.5 times. The content of water-soluble forms of heavy metals increases with depth in the most remote soils from the spoil heap. In the course of calculations of the total coefficient of soil pollution, it follows that the soils have excessively dangerous and hazardous level of pollution. Conclusion. Thus, in the course of studies of the spoil heap of the mine «Tsentralnaya» of the Karabash ore district, the direct influence of the dumping mass on the contamination of soils of the surrounding areas by migration of heavy metals from the surface of the spoil heap by hydro-genic runoff was established. As a result, rock heterogeneities, less soluble, partially restrain the oxidation rate, forming reducing conditions. The elemental composition of the rocks showed a high content of heavy metals, making this waste rock a source of heavy metals to the surrounding environment. Resume. The instability and heterogeneity of the ongoing geochemical processes in the waste rock mass of the slag heap has been revealed, which leads to leaching of the rock mass slowly over time. Spreading of products of destruction of mineral mass of the spoil heap can be traced in soils up to 800 metres away. As a result of hydro-genic flows from the spoil heap, the soils, have a dangerous and extremely dangerous degree of contamination. As suggestions for practical application and direction of future research, the importance of this work can be noted, which can serve as a foundation for the study of such technogenic mineral formations with a view to their secondary utilization, as well as for determining the most appropriate methods of remediation of contaminated soils.

Silver, cobalt and nickel mineralogy and geochemistry of shale ore in the sediment-hosted stratiform Nowa Sól copper–silver deposit, SW Poland

The Nowa Sól deposit is a part of the newly discovered Northern Copper Belt and is situated some 30 km NW of the Lubin–Sieroszowice mining district (the so-called New Copper District) in SW Poland. The ore horizon spans across the upper part of the Lower Permian (Rotliegend) terrestrial redbeds and the lower part of the Upper Permian (Zechstein) marine rocks. It comprises three lithotypes: sandstone, shale and carbonate. The high-grade shale ore has polymetallic characteristics and is a crucial host for by-product metals such as Ag, Co and Ni (studied in this paper), but also Mo, V and Re. The results of bulk-rock and electron microprobe as well as mineralogical (optical and scanning electron microscope) data of the mineralized, organic-rich shale ore from the Nowa Sól deposit are presented. This thin stratigraphic horizon, ranging from 0.06 to 0.59 m, shows notable concentrations of critical metals, including on average 15.9 wt% Cu, 715 grams per tonne (g t -1 ) Ag, 318 g t -1 Co and 345 g t -1 Ni. It constitutes less than 10% of the total ore mass, but accounts for 36% of the Ag, 40% of the Ni and 42% of the Co found within the deposit. The ore sulfides in the mineralized shale in the Nowa Sól deposit include chalcocite, djurleite and bornite, accompanied by digenite, covellite, tennantite, galena, sphalerite and pyrite. The Ag content within the Cu sulfides exhibits a linear decrease: chalcocite > djurleite > bornite. Three primary Ag minerals are identified within the shale ore, namely native Ag, Ag amalgam and stromeyerite. Two types of Ag amalgam are observed: Hg-rich and Hg-poor. Cobaltite and gersdorffite represent the primary Co and Ni minerals, occurring as micrometre-sized inclusions within chalcocite and djurleite. Textural observations suggest that the Ag, Co and Ni mineralization postdates the major phase of Cu sulfide precipitation. It is shown that in the Nowa Sól deposit, the Kupferschiefer horizon has acted as a geochemical barrier for the above-mentioned metals during protracted time, from early syndepositional to late epigenetic stage of basin evolution. Supplementary material: The supplementary material contains the results of the electron microprobe analyses and the specific experimental conditions employed for these analyses – available at https://doi.org/10.6084/m9.figshare.c.6873631

Serpentine Overburden Products-Nature-Inspired Materials for Metal Detoxification in Industrially Polluted Soil.

The possibility of plants growing on serpentine soils and the ability of serpentine minerals to accumulate significant amounts of metals was the basis for developing a method for using serpentine-containing materials to restore vegetation in areas with a high level of metal pollution. Serpentine-containing products obtained from phlogopite mining overburden (Kovdor, Murmansk region, Russia) with and without thermal activation were used in a field experiment on the remediation of industrially polluted peat soil. According to the geochemical mobility of the components, one of four fractions was allocated depending on the acidic (HCl) concentration of the solution used for the material treatment: readily mobile (0.001 mol/L), mobile (0.01 mol/L), potentially mobile (0.1 mol/L), and acid-soluble (1.0 mol/L). This study showed that the addition of serpentinites to peat soil changed the fraction composition. The most significant changes were noted for serpentinite components such as Ca and Mg: their concentrations increased 2-3 times even in the smallest portion of serpentine material. On the contrary, the contents of metals in the readily mobile fraction decreased 3-18, 3-23, 5-26, and 2-42 times for Cu, Ni, Fe, and Al, respectively. The main factor causing the decrease in metal mobility was the pH rise due to the release of Ca and Mg compounds into the soil solution. This study showed that the addition of serpentine-containing material at 25 vol.% to peat soil was sufficient to create a geochemical barrier with a stable-functioning vegetation cover. All serpentine-containing materials are recommended for the remediation of large industrially polluted areas.

Geospatial patterns and geochemical compositional characteristics of molybdenum in different mediums of an urban environment

Urban areas are characterized by the presence of certain potentially toxic elements including molybdenum (Mo). Therefore, compositional data analysis combined with geospatial mapping was applied in this study to reveal the spatial distribution characteristics of Mo in courtyard surface dust (dust), soils, and river sediments (sediments), to identify potential sources of Mo, and to reveal Mo geochemical associations in different urban environmental mediums. The mean contents of Mo decreased in the following order: dust (11.9 mg/kg) – soil (5.84 mg/kg) – sediment (4.87 mg/kg). The highest maximum Mo content among the studied mediums (61.8 mg/kg) was detected in dust. It was the only investigated medium where a very high level of Mo enrichment was observed (4.4% of samples). Moreover, a significant level of enrichment predominated in dust (47% of samples) whereas in soil, moderate enrichment prevails (68.5%). A significant correlation of Mo contents was observed with Zn contents in all the studied mediums, and with Ca contents in soil and sediments. A significant negative correlation was observed only between Mo contents in dust and sampling site altitudes suggesting that high-rise buildings might play the role of geochemical barriers. Principal component analysis, k-means and hierarchical clustering showed that in the geogenic elements soil group Mo showed an affinity to be bound by Fe/Mn oxide/hydroxides whereas the Mo coprecipitation, complexation and absorption by carbonates predominated in the Mo-related soil group (geochemical compositional association of Mo, Zn, Cu, Pb, and Ca) under anthropogenic influence. For dust, the geochemical compositional association was the same, but in the geogenic-related group, Cu was the most closely associated element instead of Zn. The spatial location of the Mo-related group of samples identified by k-means clustering indicates that Mo concentrate processing plant may be a potential source of Mo introduction into the urban environment.

A Complex Compound of Mechanochemically Modified Humic Acids and Fe(III) as a Base of a Geochemical Barrier

A Complex Compound of Mechanochemically Modified Humic Acids and Fe(III) as a Base of a Geochemical Barrier

Высокоточный элементный анализ образцов горных пород и археологических артефактов методом рентгеновской фотоэлектронной спектроскопии

Introduction. Despite a fairly wide range of methods currently used for the chemical and elemental analysis of rocks and archaeological artifacts, many questions regarding the qualitative and quantitative accuracy of the analysis and the distribution of elements over the surface and volume of the sample with a high degree of locality remain open. In this regard, to solve these issues, in this work, for the first time, the method of X-ray photoelectron spectroscopy (XPS) was proposed and tested, which allows unambiguous and high-precision chemical identification of an object and the construction of its elemental map of the surface and volume. Materials and methods. The physical principles of the XPS method operation, which determine its record high qualitative and quantitative accuracy, are considered, a description of one of the most highly efficient X-ray photoelectron spectrometers Escalab 250 Xi, features of its operation and methods of adaptation for the study of rocks and archaeological artifacts are given. A special methodological advantage is the possibility of sample preparation and research under ultrapure conditions of ultrahigh vacuum. Results. XPS spectra were obtained in a wide range of photoelectron binding energies, which makes it possible to cover a fairly wide range of chemical elements that make up rocks and archaeological artifacts. With a high degree of spatial locality – at the level of 30 μm – elemental maps of the objects under study were built. Using the additional advantage of the method, based on the analysis of the energy position and the shape of the photoelectron spectral line, the chemical states of the elements that make up the samples were determined. Discussion. The obtained results of high-precision chemical analysis, combining both the general composition of the elements of the test sample as a whole and their spatial distribution with a high degree of locality, make it possible to achieve greater unambiguity in the identification of the objects under study compared to currently used analysis methods. Such high accuracy makes it possible to establish a correspondence between the composition of the rock and the archaeological artifact from the same area. The non-destructive nature of the XPS method, combined with ultrapure analysis conditions, makes it possible to ensure the safety of often unique objects. Conclusion. As a result of the study, it was shown that the XPS method can be quite effectively used for high-precision qualitative and quantitative analysis of rocks and archaeological artifacts, which is achieved both by the features of the method itself and by sample preparation and study of materials in ultrapure conditions of ultrahigh vacuum. The advantage of the method is the combination of a number of possibilities, such as not only the elemental, but also the chemical composition of objects, as well as the possibility of chemical mapping of the surface and analysis of the depth of the object with high spatial resolution. The research results can be used in solving a wide range of problems – from archeology to the development of mountainous areas, in particular, solving environmental problems by developing a scientific reserve for creating effective geochemical barriers. Further research should be focused on the development of techniques for adapting the XPS method to obtain three-dimensional tomographic models of the studied objects, which will improve the quality of their identification, in particular, from the point of view of geology and archeology.

Multi-scale sedimentary facies controls on fluvial sandstone-type uranium accumulation process in the Songliao Basin, NE China

The relationship between uranium mineralisation and sedimentary facies in a fluvial depositional setting remains a challenging topic. However, the specific effect of muti-scale sedimentary facies control on meandering sandstone-type uranium enrichment is poorly understood. Based on sedimentological, geochemical, mineralogical, and petrophysical analyses, three third-order sequences (SQ1, SQ2, and SQ3) composed of four systems tracts in meandering deposits were identified in the Sifangtai Formation of the northern Songliao Basin. Four subfacies (channel, levee, flood, and abandoned channels) and seven microfacies were identified in meandering rivers, exhibiting spatio-temporal migration of sedimentary fillings. Here, uranium deposits were mainly enriched in semi-abandoned channel deposits during the lowstand systems tract (LST) period of SQ1. Stable-distributed and thick-layered industrial-grade uranium deposits occurred in a positive rhythmic rock assemblages, exhibiting high-frequency variation from thicker medium–fine sandstone to thin charcoal-rich siltstone–fine sandstone. Rapid tectonic uplift and warm-semi humid climate during early Sifangtai period controlled sequence growth and sedimentary filling. Furthermore, sequence and sedimentation during the LST period mediated the formation of uranium-rich rock assemblage and fluid migration pathway, reacting on the abundance, location, and distribution of uranium enrichment. Ultimately, a conceptual model of the sequence and sedimentary control on uranium accumulation was established in the context of meandering rivers. This model revealed that semi humid-warm climate and tectonic inversion (74.9–72.2 Ma) control meandering river, sedimentary hiatus, and charcoal-rich uranium-hosted rock series formation in the LST. Enhanced Cenozoic tectonic uplift (38.0–10.0 Ma) and continental weathering prompted uranium-rich fluids along steep paleotopography, migrated to geochemical barriers of charcoal-rich rock series, and reductive mineralisation around semi-abandoned channel deposits. Our results illustrate the importance of examining multi-scale sedimentary facies to interpret the uranium accumulation process of meandering deposits, ultimately contributing to uranium exploration in similar settings.

Biogeochemical In Situ Barriers in the Aquifers near Uranium Sludge Storages

The long-term operation of uranium sludge storages causes serious problems: it contaminates the neighboring aquifers with dangerous substances (uranium, nitrate, ammonium, and sulfate). To purify the aquifers can be costly and time-consuming; therefore, it is important to use the potential of in situ conditions, e.g., the aboriginal microflora and its ability to biologically remediate water reservoirs. In this work, we study the geological, geochemical, and microbiological characteristics of groundwater contaminated by uranium sludge storages resulting from the production cycles of four Russian chemical plants. All of the sites under consideration were extremely contaminated with nitrate (up to 15 g/L); in each case, we used denitrifying bacteria as a dominant group of microorganisms for purification. Our laboratory studies showed that microbial stimulation of water samples by milk whey promotes O2 and nitrate removal; this, in turn, started the cycle of anaerobic processes of authigenic precipitation caused by the reduction of iron and sulfate in the system. Thus, a mineral geochemical barrier preventing uranium immobilization formed. As a result, the uranium of the liquid phase decreased about 92–98% after 3–6 months (decomposition time depends on the nitrate concentration in the groundwater probe). The resulting amorphous biogenic phases contain sulfur, iron, phosphorus, and uranium.

Ecological and Geochemical State of Soil Cover in Gusinoozersk in the Zone of Influence of Coal Thermal Power Plant

The pollution of the topsoils of the city of Gusinoozersk (Republic of Buryatia) under the influence of emissions from State District Power Plant (SDPP) which used the Okino-Klyuchevskiy brown coal as fuel was studied. The content of 14 elements (Sr, As, Co, Mo, Sb, V, Cu, Ni, Cr, W, Zn, Bi, Cd, Pb) in bulk samples, as well as in the fraction of physical clay (particles with a diameter 10 µm, PM10) and in samples of brown coal and ash from the SDPP. Strontium, As, Co, Mo, Sb, V are the priority pollutants in the soils of Gusinoozersk with higher concentrations of most elements in the PM10 fraction. Soils and the PM10 fraction in the industrial operating subzone are the most polluted with Sr, As, Co, V, Cu, Mo, Ni, Cr, which are contained in the fly ash of the Gusinoozerskaya SDPP. Most of the territory (57% for soils in general and 47% for the PM10 fraction) is characterized by a low level of pollution (Zc = 8–16). Arsenic poses the greatest environmental hazard; in the PM10 fraction, its concentrations exceeded the MPC in 90% of the studied samples. In soils and their PM10 fraction, the leading factors for the accumulation of elements are the content of Fe2O3, organic matter, soil texture, alkaline-acid conditions, and belonging to a functional zone, which determine the formation of various classes of geochemical barriers. The polluting effect of brown coals depends on the content of heavy metals and metalloids in them. Comparison of the chemical composition of the Okino-Klyuchevskii brown coal and ash from the Gusinoozerskaya SDPP and the Kansk-Achinskii coal and ash from the Central Thermal Power Plant of Severobaikalsk showed that the brown coal and ash from Severobaikalsk were slightly enriched in metals and metalloids, which significantly reduced their accumulation in soils.