The mobility of thallium from bottom soil of the Silesian-Cracowian zinc-lead ore deposit region (Poland)

Abstract

Thallium is a nonessential toxic element that may pose an environmental hazard. A crucial factor for the toxic effect of Tl is the mobility of the element. The aim of this work was to investigate Tl mobility in typical soil samples formed over six different lithological backgrounds (glaciofluvial sands and gravel, slope-wash sands and loams, siltstones and conglomerates, loesses, dolomites and ore-bearing dolomites) from the south-eastern part of the Silesian-Cracowian zinc-lead ore deposit region in Poland. Five geochemical fractions (water soluble, ion-exchangeable/carbonates, reducible, oxidizable, and residual) were obtained by using a sequential extraction scheme coupled with flow-injection anodic stripping voltammetry. The results showed that the Tl in most of the soils investigated is mainly entrapped in the parent matter, which is immovable and inert in terms of environmental effects. However, a significant part of the Tl was found in the reducible and oxidizable fractions of the soil formed over ore-bearing dolomites. It highlights that the environmental hazard caused by Tl should be measured by the content of mobile Tl rather than by its total content.