Survey on the metal contamination of agricultural soils in Georgia

Abstract

There is only sparse information on the metal contamination of agricultural soils in the former Soviet Union and the development of impacts during the process of transformation to a private structure of production. In this study a first overview on the metal load (Pb, Zn, Cu, Cr, Mn) of agricultural soils in central and eastern regions of Georgia is given using 251 subsamples from 106 profiles on 37 plots. While the data sets for lead (Pb) and chromium (Cr) are rather homogeneous and range only within narrow limits, the contents of zinc (Zn) and copper (Cu) vary much more. Additionally, manganese (Mn) was tested. Here the data vary largely, which is probably due to the natural soil loads. Very low loads for all investigated metals are typical for communally used pastures (Allmende) and especially for a biologically managed farm. On the contrary, Cu loads frequently exceed the median by more than five to ten times (the maximum value is 1023 mg kg−1) in vineyards. The comparison of complete soil profiles proves that this is due to the application of copper sulphate for pest control. In the Bolnisi region south of Tbilisi extremely high loads in the upper soil horizons are found not only for Cu, but for Zn as well, ranging up to 794 mg kg−1. Compared to all other data, the loads for Pb and Cr are also high in several samples. Cu, Zn and Pb are significantly correlated to one another in the Bolnisi region. This striking situation most probably results from the frequent irrigation of the plots by industrially contaminated water from the Mashawera River. Due to economic deficiencies the application of chemicals in Georgian agriculture has dropped heavily since 1990. Consequently, the metal contamination of agricultural soils in general is rather low, being far below western European tolerance limits. Intensive pasturing might even cause values close to the natural loads due to erosion and/or the export by the way of plants and livestock. On the other hand, some specific types of land use cause serious environmental problems. This is especially true for vineyards and plots that are irrigated with contaminated water. Overgrazed plots tend to soil erosion. Copyright © 1999 John Wiley & Sons, Ltd.