Heavy metal compounds in a soil of technogenic zone as indicate of its ecological state

Abstract

The emissions from the Novocherkassk power station comprise 1% of the total volume in the Russian Federation and up to 58% of the emissions in the Rostov oblast. The aim of this work was to assess the regularities of heavy metals accumulation and transformation in soils subjected to aerosol emissions from the power station on the basis of the fractional composition of their compounds. Studies have been conducted on the soils of monitoring plots distances from the power station (1.0–20.0 km) during 15 years. The monitoring plots located on fallow areas. Soil samples for the determination of soil properties and the contents of heavy metals compounds were taken from a depth of 0–20 cm. The soil cover in the region under study consisted of ordinary chernozems, meadow-chernozemic soils, and alluvial meadow soils. The total amount of heavy metals in soils was determined by X-ray fluorescence. Metals in soil extracts were determined by atomic absorption spectroscopy. The fractional composition of heavy metals was determined using combined fractionation. A combined approach for fractioning metal compounds in soils on the basis of and parallel extractions (1 N NH 4 Ac, pH 8; 1% EDTA in NH 4 Ac; and 1 N HCl) was used. Aerosol emissions from the power station are the major agents of technogenic impact on the soils under study in the Rostov oblast. The highest degree of contamination with metals (mg/kg: Ni - 64, Cd – 1.3, Cr - 145 and As – 12) was observed for soils located within a radius of 5 km from the power station along the predominant wind direction. It was marked the rise of metals mobility in the polluted soils and predominant participation of Cr and Ni organic-mineral complexes among their mobile species. The increasing of Cd mobility was provided predominantly by exchangeable forms and specifically sorbed by Fe-Mn (hydr)oxides. The environmental contamination hazard increases with the decreasing metal-buffering capacity of soils.