Ivan V. Timofeev

Geochemical transformation of soil cover in copper–molybdenum mining areas (Erdenet, Mongolia)

PurposeThe aim of the present study is to evaluate geochemical transformation of soil cover in the territory of Erdenet (Mongolia) and to assess the environmental risk associated with soil cover contamination. The objectives of the present study included: (1) the determination of heavy metals (HMs) and metalloids contents in surface horizons of background and urban soils and the assessment of geochemical transformation of the city’s soil cover; (2) the identification of elements’ associations and patterns of their spatial distribution in the soil cover of the city; (3) the assessment of environmental hazard, related to contamination of soils with complexes of HMs and metalloids.Materials and methodsSoil–geochemical survey was conducted by the authors in the summer periods of 2010 and 2011. In total, 225 samples, including 32 backgrounds, were collected. Bulk contents of HMs and metalloids in soil samples were analyzed by mass-spectral method with inductively coupled plasma at All-Russian Research Institute of Mineral Raw Materials (Moscow) using Elan-6100 and Optima-4300 devices (Perkin Elmer, USA).Results and discussionMo, Cu, and Se appeared to be the priority pollutants nearly in all land-use zones. The maximum accumulation of Mo, Cu, Se, As, Sb, and W is restricted to the industrial area where total pollution index of soils (Zc) equals 74.8. Three technogenic associations of elements, derived mainly from petrochemical features of Erdenet ore field and characterized by similar spatial distribution within the city, are identified. Environmental assessment of surface soil horizon geochemistry in Erdenet showed that 1/5 of its area has dangerous and extremely dangerous levels of soil pollution.ConclusionsExperience of the environmental–geochemical assessment of soil cover in the impact zone of mining enterprises could be useful for other fields of the non-ferrous metals with high lithological–geochemical heterogeneity of the territory. It suggests the need of accounting for the geological diversity and specific features of metallogeny of an area. Geochemical indices local enrichment factor/local depletion factor should be calculated against the individual background values for each soil-forming rock. Such approach allows more accurate assessment of the degree of technogenic geochemical transformation of soils and the environmental hazard of pollution.

Trace Element Composition of Poplar in Mongolian Cities

Purpose. The aim of our work was to assess changes in the trace element composition of poplar leaves in large cities and mining centers of Mongolia. The objectives of the study included: (1) to reveal the biogeochemical background features and changes in the trace element composition of poplar leaves in urban and mining landscapes; (2) to determine the degree of technogenic disturbance in the chemical composition of urban vegetation; and (3) to assess the functioning and ecological status of poplars under technogenic impact. Materials and methods. Poplar hybrids, which compose about 75 % of the urban woody plantations, were sampled in Ulaanbaatar (77 samples) in the mid-summer of 2008, Erdenet (30 samples) in 2011, Darkhan (19 samples) in 2011, and Sharyngol (21 samples) in 2013. Bulk concentrations of 54 heavy metals in the samples of the dry plant material were measured by inductively coupled plasma mass spectrometry (ICP-MS) on Elan-6100 and Optima-4300 analyzers. Results and discussion. The local biogeochemical background of the Mongolian cities under consideration differs from the mean global values in the higher concentrations of Cd, Sr, As, and Zn. The concentrations of Be, V, Pb, Cr, and Ni in plants of the background areas are lower than their global values. The maximum coefficients of the biogeochemical transformation, Z v , were revealed in Ulaanbaatar. In the other cities, the values of Z v in the industrial zones were higher than those in the residential zones by 1.5–2 times. The trace element ratios characterizing the balance in the provision of metabolic processes confirm the conclusion about the satisfactory state of the urban trees.

State of the environment of urban and mining areas in the Selenga Transboundary River Basin (Mongolia Russia)

The pollution of the soil cover, river water and bottom sediments in the Ulaanbaatar and Ulan-Ude cities and the Erdenet and Zakamensk mining centers was assessed using the data of geochemical surveys in 2011–2015. In Ulaanbaatar, the highest pollution with Pb, Cd, Zn, Mo, Cr, and Cu is revealed in the central industrial–transport–residential area. Emissions from thermal power plants and motor vehicles are the main sources of pollutants. In Ulan-Ude, the highest concentrations of Pb, Cd, Sb, and Sn are observed in the soils of the industrial zone with various engineering and manufacturing enterprises. The topsoils in the mining centers are contaminated with ore and accompanied elements: Mo, Cu, As, Sb in Erdenet, and W and Mo, W, Bi, Cd, Pb, and Sb in Zakamensk. The extremely hazardous level of the soil pollution in Erdenet was revealed in the mining complex area, while in Zakamensk, it occupies about half of the city’s territory. The Ulaanbaatar city’s effect on the trace element composition of water and bottom sediments in the Tuul River during the summer floods is insignificant, in low-water season content of dissolved Pb, Cd, Zn, Co, Sr, Ni and Cu, Co, V in suspension increase many times. In the Selenga River lower course near Ulan-Ude, the floodwater has high concentrations of dissolved Cu, Co, V, Ni and is slightly enriched with suspended V, Bi, Sb, Sn, Mo; the concentrations of heavy metals in bottom sediments remain unchanged. The mining centers exert a local impact on the river network.

Potentially toxic elements in urban soil catenas of W-Mo (Zakamensk, Russia) and Cu-Mo (Erdenet, Mongolia) mining areas

PurposeThe aim of this study was to characterize the conditions of the lateral migration of potentially toxic elements (PTEs) and to identify the zones of their accumulation in soil catenas of ore-mining landscapes in the cities of Zakamensk (Buryat Republic, Russia) and Erdenet (Mongolia) which are situated in the basin of the Selenga River.Materials and methodsEight soil catenas across the river valley with 31 pits in Zakamensk area and five catenas with 15 pits in Erdenet area were studied. Soil samples were collected in four landscape–geochemical positions: autonomous, on tops of the hills; trans-eluvial, on slopes of river valleys; trans-accumulative, at the footslopes; and superaqual, on the river floodplains. The total contents of 16 PTEs in the 148 samples were determined by mass spectrometry and by atomic emission spectrometry with inductively coupled plasma.Results and discussionIt is found that the chemical composition of undisturbed soils is greatly affected by the widespread distribution of volcanic rocks enriched with W, Mo, Cd, Bi, and Sr in Zakamensk and with V, Co, Sr, and As in Erdenet. The difference between geochemical positions is relatively small. Under the influence of technogenic loads in the cities, the concentrations of PTE change along soil catenas increases by an order of magnitude. For chalcophile elements—Mo, Bi, Pb, Sb, and Cu in Zakamensk and Cu, Zn, Mo, Cd, Sn, and W in Erdenet—the type of their lateral distribution in the soil catenas changes because of the intense migration from the tailings and facilities with water and air flows. The accumulation of PTEs takes place on the chemisorptive (V, Co, Ba, As, Cr, and Ni), gley (Mo and Sb), organomineral (Sn), and alkaline (Sr and W) lateral geochemical barriers (LGBs) confined to subordinate positions. The artificial technological LGBs are formed due to the increased content of sand derived from the tailings by water erosion in Zakamensk and the input of silt particles windblown from the technogenic sources in Erdenet. This causes the rise in the concentrations of major ore elements (Mo, W, and Cu) and the accompanying elements (Pb, Bi, As, Sr, Cr, and Ni).ConclusionsThe results of soil–geochemical studies using the catenary approach and concept of LGBs made it possible to understand the main features of migration and fixation of PTEs in soils of the mining centers. They indicate the formation of a system of LGBs with intensive accumulation of major ore elements and associated ones in the subordinate landscapes of Zakamensk and Erdenet.

Ecological and Geochemical Assessment of Woody Vegetation in Tungsten-Molybdenum Mining Area (Buryat Republic, Russia)

Biogeochemical studies performed in the impact zone of the Dzhida tungsten- molybdenum mining and processing enterprise in Zakamensk (Buryat Republic, Russia) in 2013 showed that the needles and bark of Larix sibirica Ledeb. and the leaves and bark of Betula platyphýlla Sukacs are characterized by certain changes in their trace element (TE) composition. The total index of the biogeochemical transformation Z v which sums all the positive and negative deviations of TE contents from the background values for larch and birch in the city averaged 95 and 46 for their assimilating organs and 30 and 25 for their perennial organs, respectively. This was caused by the increased uptake of W, Mo, V, Pb, Bi, Cd, and Co in the city. The close correlation between TE concentrations in soils and plants was observed for the elements of the strong and moderate biological capturing, including cationic Cu, Zn, Sr, Cd, and Ba and anions of the ore elements W and Mo and the associated Bi. The most intensive TE accumulation was found in the larch needles due to the wax layer which firmly fixes the dust enriched with TEs. Indication of the ecological state of urban woody plants revealed that their organs contain the increased concentrations of Pb and Fe and suffer from the Mn deficiency, which attests to disturbance of photosynthetic processes, most pronounced in the residential area. Birch leaves are characterized by a very low Cu/Zn ratio which detects the imbalance of these elements participating in the synthesis of enzymes.

Soil cover geochemistry of mining landscapes in the South-East of Transbaikalia (City of Zakamensk)

Presented is a detailed characterization of the present state and pollution of soil cover in the influence area of the Dzhidinskii tungsten-molybdenum plant which takes into consideration the spatial geological inhomogeneity and the functional purpose of urban territories. As part of the investigation, we determined the content levels of heavy metals and metalloids in background soils, and the elements which are the main pollutants of urban soils in the zones of different functional purposes, ascertained the degree of technogenic geochemical transformation of soil cover in the city of Zakamensk, and identified the leading soiland landscape-geochemical factors for accumulation of heavy metals and metalloids in the urban topsoil (0−10 cm) horizons. An assessment was also made of the ecological hazard of soil pollution by a set of heavy metals and metalloids in the main functional zones of the city. A soil-geochemical survey was carried out, and the ICP-MS method was used to determine the total content levels of 14 heavy metals and metalloids of hazard classes I−III as well as Be, Sn, Cs and Bi. The elements were determined, which are the main pollutants of the soils in Zakamensk: W, Bi, Cd, Pb and Mo. The study revealed a need to take into account the metallogenic specific character and geological inhomogeneity of the area by using the local coefficients of concentration (EFl) and dispersal (DFl) which must be calculated not with respect to the average regional background but from the individual (for each parent material) background value in order to more accurately determine the degree of technogenic geochemical transformation of soils, and the ecological hazard of pollution. It is suggested that the ecological hazard should be assessed on the basis of the Integrated Pollution Index (IPI) which is calculated with respect to the world’s average concentrations of heavy metals and metalloids in soils and takes into account hazard classes of elements.