Study of geochemical features of soils on the territory of an abandoned coal mining area using geoinformation technologies

The article describes the results of a study of the geochemical features of soils on the territory of an abandoned mining area. The Kizel coal basin (Russia) is of particular interest for studying the consequences of technogenic and post-technogenic transformation of the natural environment. The study of the soil as a deposit medium made it possible to identify geochemical indicators of the negative impact. Such a detailed study of the distribution of chemical elements in this area was conducted for the first time. Geoinformation system and maps with interpolation were created to study the spatial distribution of metals and metalloids in soils. Umbric Retisols Abruptic and Haplic Retisols Abruptic soils are common in the territory. Sampling for geochemical testing was carried out from two horizons: humus and podzolic. Sampling from two depths made it possible to identify elements that continue to be contaminated at the time of the study. A total of 103 sample plots were established in the study area. The results obtained were compared with the background of the natural region of the Western Urals to identify the contribution of technogenesis. As a result, the coefficients of concentration and dispersion of chemical elements were calculated. Due to this, elements were identified, the accumulation of which occurs on the territory of the Kizelovsky coal basin. To identify the current and accumulated pollution, the ratio between the humus and podzolic horizons was calculated. As a result, it was found that at the moment in the humus horizon in some areas there is a high accumulation of Co, Mn, Ni and Sr. The geochemical series of the territory for the humus and podzolic horizons was obtained: Fe > Ti > Mn > Sr > Cr > V > Zn > Ni > Co > Pb > As. Data on the geochemical specificity of the territory of the Kizel coal basin have been obtained. The created geoinformation database reflects the physical and chemical properties of soils, metals and metalloids content, dispersion and accumulation coefficients, coefficients of the ratio of the humus and podzolic horizon. Based on it, it is possible to obtain data on the geochemical features of the territory, geoecological characteristics, spatial distribution of metals and metalloids and identification of pollution sources. Co (24 ± 2.8 mg/kg), Mn (1100 ± 155 mg/kg), Ni (69 ± 9.3 mg/kg), As (10 ± 3.5 mg/kg), Cr (178 ± 20 mg/kg), Zn (80 ± 7.8 mg/kg) and Sr (221 ± 26 mg/kg) accumulate in the humus horizon. Co (24 ± 1.8 mg/kg), Mn (1000 ± 103 mg/kg), Ni (60 ± 6.4 mg/kg) and Cr (153 ± 15.2 mg/kg) accumulate in the podzolic horizon.

A new test for plant bioaccessibility in sulphidic wastes and soils: A case study from the Wheal Maid historic tailings repository in Cornwall, UK

Currently, bioaccessibility testing at contaminated sites is dominated by techniques designed to assess oral bioaccessibility to humans. Determining the plant bioaccessibility of toxic trace elements is also important. In mining landscapes, sulphides are an important source of potentially toxic elements. Simple tests to evaluate readily leachable metals and metalloids exist but do not extract elements temporarily constrained within the sulphide fraction. Sequential extractions describe the association of trace elements with different geochemical fractions but are time consuming, costly and provide excessive detail. This paper proposes a new test for plant bioaccessibility in sulphidic mine wastes and soils that uses hydrogen peroxide to simulate environmental oxidation. The bioaccessible fraction determined is operationally defined and does not predict actual plant uptake. The test targets a) the portion of an element that is currently available in the pore water for uptake by plant roots and also b) the fraction that is temporarily constrained in sulphide minerals but may become available upon oxidation of the substrate. A case study was conducted at a historic mine waste repository site in Cornwall, U.K. where near total As concentrations were extremely elevated and Cd, Cu, Pb, Sb and Zn were also high. Our test determined that bioaccessible concentrations of As, Cd, Cu and Zn and to a lesser extent Sb and Pb were highest in samples of pyritic grey tailings. This is attributed to sulphide mineral oxidation and, particularly for Cd and Zn, the dissolution of soluble secondary minerals. High As concentrations in the marbled tailings were not bioaccessible. Results from the case study show that this new test provides useful information on the future bioaccessibility of contaminants, allowing for classification of mineralised sulphidic waste materials which otherwise cannot be obtained using established geochemical and mineralogical techniques. Furthermore, the test is rapid, repeatable and cost effective.