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CONCENTRATION OF MOBILE FORMS OF HEAVY METALS IN THE SOILS OF URBAN VILLAGE STEPNOE

Majeed Majeed

Abstract

The urban village Stepnoe has a size of 8 km2 and a population of about 12,340 inhabitants (according to data obtained in 2015). It was founded in 1767 and since 1967 it has been the administrative center of the Soviet district of Saratov region. We studied the distribution of mobile forms of heavy metals in the soils of the urban-type settlement Stepnoe, the territory of which can be attributed to a group of landscapes of small settlements, villages and localities. Soil sample points were distributed taking into consideration the wind rose, peculiarities of the micro-topography, distribution of the building plans and basic amenities. In accordance with State Standards, a test was conducted on the upper layers of the soil horizon «?» to the depth of 5 cm where basic pollutants from the atmosphere are usually accumulated. Determination of heavy metals in the soil was carried out by atomic absorption spectrometry with flame atomization spectrophotometer "Quantum-2AT". Mobile acid-soluble forms of metals (Cu, Zn, Ni, Cd, Pb) were determined in 1M HNO3 extracts. In recent years, these extractors have been successfully used for analyzing soils subject to anthropogenic impacts. From heavily contaminated soils, 1M HNO3 extracts 90-95% of heavy metals from their gross content. The ratio of soil to solution was 1: 10, for peat soils-1: 20. To determine the ecologically dangerous concentrations of heavy metal in the soil cover, the actual concentration of each heavy metal was compared with its maximum permissible concentration (MPC), while calculating the heavy metal hazard ratio ??. A geochemical order for the mobile forms of heavy metals in the territory of the urban settlement Stepnoe was as follows: Ni>Zn>Pb>Cu>Cr>Cd (based on average concentrations) and Ni>Cu>Pb>Cr>Zn>Cd (based on increments above normal indices). Analysis of the obtained laboratory studies shows that the determined elements can be divided into two groups: the first group ? Nickel, lead, copper, and samples in this group had an excess over MPC; the second group ? chromium, zinc and cadmium, in this group there was no excess over MPC. The calculation of the total pollution coefficient (Zc) showed the following; in the studied area Zc varied from -0.8 to 3.92 with an average value of 0.51. All 30 samples (100%) belonged to a category with acceptable levels of contamination (Zc from 0 to 16). In normative documents, the gradation used for Zc is calculated from the concentration coefficient (from an excess over the background), we also calculated the Zc from the hazard coefficient (from an excess over the MPC).

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DOI resolver: doi.org/10.5593/sgem2019/3.2/s13.014

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