Geochemistry of Lakes in a Zone Impacted by an Arctic Iron-Producing Enterprise

Abstract

The paper presents data on the chemical composition of waters and bottom sediments in lakes variably affected by liquid wastes from facilities of the Olkon Joint-Stock Company in Olenegorst, Murmansk oblast, which mines and processes iron ores. Since Olkon started operating, the composition of water in nearby water bodies has underwent significant changes. The mineralization (TDS) and pH of the lacustrine waters have increased (to 100 mg/L and 7.6 respectively). The qualitative composition of the water has also changed (the water type has changed from hydrocarbonate to sulfate), as also have the proportions of the dominant cations. The waters of the lakes have enriched in nitrogen-group compounds. The $${\text{NO}}_{3}^{ - }$$ concentrations in some of the lakes are higher than the concentrations of the dominant ions (Na+, K+, and Cl–) recalculated into equivalent concentrations. The inflow of contaminants with the waste waters has suppressed biological productivity and reduced concentrations of organic compounds in the lacustrine waters. The waters of the lakes that received waste waters form the iron-producing facilities contain the highest Ni, Cu, Co, Al, and Sr concentrations, whereas the Fe concentrations are the lowest, which is reportedly explained by a decrease in the concentrations of organic compounds and an increase in pH of the lacustrine waters (and a corresponding decrease in the Fe solubility). The paper reports data on the speciation of metals in the lacustrine waters: Fe and Cu occur in them mostly in compounds with organic ligands Fe(III)–L and Cu(II)–L; Mn is contained as Mn(II)– $${\text{SO}}_{4}^{{2 - }}$$ /Cl–/OH– compounds; and Ni, Co, and Zn form compounds with hydroxyl groups Ni(II)–OH, Co(II)–OH, and Zn(II)–OH. Concentrations of heavy metals in the lacustrine bottom sediments depend on the dominant form of their occurrence in the waters. The surface layers of the bottom sediments are significantly enriched in heavy metals (Ni, Cu, Co, Cd, Pb, As, Hg, Fe, and Mn), which are tens of times higher than the background concentrations. The highest values of the contamination factor (Cf) and degree of contamination (Cd) were found in the lakes contaminated with waste waters from the facilities.