Translocation and mobility of thallium from zinc–lead ores

Abstract

Thallium is a toxic, non-essential element. Zinc–lead ores are a known source of thallium pollution. The aim of this paper was to investigate the translocation of thallium from zinc–lead ores from the Cracow–Silesia Upland due to ore flotation processing and natural processes and the element's mobility in these samples as determined by sequential extraction in accordance with a modified BCR procedure. The oxidizable fraction of zinc–lead ores is the major source of thallium dispersion in the environment. During flotation, the galena and blende concentrates are significantly enriched with thallium, which is mainly located in the oxidizable and residual fractions. A side effect of flotation is a high concentration of thallium in the oxidizable fraction of rivulet bottom sediments. Soil formed above ore-bearing dolomites has the major part of its thallium in the oxidizable and reducible fractions. Soil formed above normal dolomites contains only 15% of the labile thallium (contained in the four fractions). This strongly supports the thesis that in typical soil the majority of the thallium is entrapped in the residual fraction. Water-soluble thallium is dependent on the labile thallium content.