Geological and Environmental Engineering | Conference paper | Published 2003

Environmental geochemistry and mineralogy of heavy metals in contaminated soils from the Almalyk mining and smelting complex area, Uzbekistan

Keywords: Heavy metals in soil, distribution, mineral forms, bioavailability, plant uptake, bioindicators, Angren-Almalyk industrial area, Uzbekistan

Abstract

Processing of numerous comparative analyses of soils, plants, and waters of mining objects of Almalyk industrial region has shown that the heavy metals collected in surface layers of soils (1-20cm) revealed a high content of heavy metals toxicants (Pb, Cd, Cu, Zn, Hg) and As, which is tens of times higher than the threshold level value. The intensity of anomalies is sharply reduced at a distance of 1-2 km from the sources of pollution. The forming aureoles are spatially focused in the prevailing wind direction. The pollution of vegetation is correlated with the pollution of soil and also is connected with the receipt of heavy metals into bio weight through the root system and to a lesser degree from atmospheric losses of polluting substances. The changes in species composition and morphological indications of plants growing on metal-contaminated soils have been revealed, the selective ability of some kinds of plants to absorption of separate elements has been established. Studies of the heavy fractions of soil samples using modern analytical instruments have enabled us to define of the occurrence forms of heavy metal toxicants. They contain various forms of primary and secondary hard-soluble ore minerals and technogenic new formations. The study of heavy fractions of soil samples by the electronic microanalyzer JEOL “Superprobe” JXR-8800R has allowed determining the occurrence forms of heavy metals. The analysis of technogenic new-formations using microanalyzer gives the opportunity to present in which form of heavy metals-toxicants are contained in outbursts of metallurgical factories. They were found to have a diverse structure and internal - structure of ball-shaped isolations. The majority of these balls contain more metals than other components. In some grains, obvious spherical (ball) structures, similar to vulcanite structures were observed. In peripheral layers of the majority of these balls, there are layers with Pb- up to 61 %, Zn- up to 73,5 %, Cu- up to 56 %, S- up to 27 %, and others. In the cores of these balls, dendrites were found, which are coalesced in silicate mass containing a high amount of iron (up to 60 %), and in other grains, the accretion of iron with copper is observed.

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