Patterns of Sorption and Desorption of Cu(II) and Ni(II) by Soils of the Norilsk Industrial Region

Abstract— The sorption capacity and strength of fixation of Cu(II) and Ni(II) by organic and mineral horizons of soils of the Norilsk industrial region have been studied in laboratory experiments with podbur, cryoturbated peat gleyzem, raw-humus cryozem, and cryometamorphic gleyzem (Spodic Cryosol, Histic Gleyic Cryosol, Turbic Cryosol, and Gleyic Cryosol). The soils were taken at key plots located at a distance of 7 to 10 km from the city of Norilsk in the western and northwestern directions. The studied soils have a high sorption capacity to Cu(II) and Ni(II). Under conditions of artificial soil contamination with sulfate solutions at concentrations ranging from 0.5 to 25 mg/L and the soil-to-solution ratio of 1 : 20, 1 : 20, the degree of extraction of metal ions ranged between 80 and 100%. The main mechanisms of adsorption in most studied horizons in the absence of competition between Cu(II) and Ni(II) are ionic chemisorption and ion exchange (the adsorption energy G varies from 8 to 13 kJ/mol). It has been found that Cu(II) is absorbed by the soil more actively and more firmly than Ni(II), which was especially pronounced in organic horizons. All the studied soils, when < 50 mg/kg of Cu(II) and Ni(II) were added to them, firmly retained the absorbed metal ions. Taking into account the significant sorption capacity of the studied soils and the ability of soils to fix firmly Cu(II) and Ni(II) in a certain range of metal concentrations, it has been suggested that it would be appropriate to consider the feasibility of setting standards for the content of heavy metals in soils based on the content of their water-soluble forms, taking into account the pH, cation exchange capacity, and Corg content of the soil.