BEHAVIOR OF HEAVY METALS IN SOIL-CONDENSATE-PLANTS SYSTEM IN THE ULAN-UDE LANDFILLS

Abstract

The impact of waste dumps on environmental components, i.e., soil, evaporating soil water (condensate) and plants is studied. It has been revealed that industrial and municipal waste dumps continue to affect significantly the environment after their closure. The behavior of heavy metals (Pb, Cu, Zn, Ni, Cd, Co, Sb, Sn, Bi, Hg, and Cr) in soils, plants, and condensate in landfill areas and beyond them (the background) has been studied in detail. It has been found out that soils, plants and condensate at landfills are enriched in heavy metals as compared to the background sites. The degree of soil contamination at waste dumps depends on the reclamation stage of the latter. The landfill soils exceed the norms of maximum permissible concentrations for heavy metals by 1.1–90 times. Concentrations of heavy metals in plants exceed the background values from 1.1 to 104 times at all dumps. The maximum level of heavy metals in plants is exceeded for Zn, Cd, Cr. In the condensate sampled at the dumps, MPC is exceeded for Cu, Zn, and Hg. Based on the analysis results, the geochemical rows of heavy metal distribution in different landfill environments were compiled: in plants – Zn Cu Cr Ni Pb Cd Co Hg Sn Bi; in condensate – Zn Cu Ni Cr Pb Sn Co Hg Sb Cd Bi; in the soil – Zn Cr Cu Ni Pb Co Sb = Sn Cd. The distribution of heavy metals in the condensate and plants is similar. In these environments, contribution of Zn and Cu is more than 80%, contribution of Cr, Ni, Pb varies from 1 to 10%; contribution of Cd, Co, Sb, Sn, Bi, Hg is less than 1%. Heavy metals are distributed in soil according to a different pattern: the main contributors are Zn and Cr (their input is more than 50%), then go Ni, Cu, Co, and Pb (their content in soil varies from 1 to 50%), followed by Sb, Sn, and Cd (their content is less than 1%). Total pollution indices (Zc) of the soil, condensate and plants have been calculated for each landfill. Based on Zc, the landfills were grouped in a ranking series, which can form the basis for assigning the sequence of landfill reclamation measures.