Heavy metal(loid)s transformation in dust at a lead smelting site

Abstract

Emitted dust is the major contributor of heavy metal(loid)s in soils located near lead (Pb) smelters, but the mechanisms for transfer of the heavy metal(loid)s in dust are uncertain. The study systematically investigated the geochemical behaviors and liberation mechanisms of heavy metal(loid)s in this process. The results show that Pb, Zn, Cd, and As in two types of dust samples exceeded the allowable standards, and about 80% of Pb and Zn were present in mobile and bioavailable fractions. More than 70% of arsenic in bottom-blowing furnace dust existed in an acid-soluble fraction, while 60% of cadmium in reducing and fuming dust existed in the acid-soluble fraction. Pb isotope results showed that 97.12% of the Pb in the topsoil came from dust emitted during the smelting process. XRD and MLA results illustrated that PbSO₄, ZnSO₄, and CdSO₄ were the major minerals in the dust, while the mineral phases of the topsoil were mainly quartz, calcite, dolomite, and muscovite. Based on a combination of mineralogical investigations and geochemical modelling, our findings suggest that liberation of the Pb, Zn, and Cd was primarily dependent on sulfate minerals under acidic conditions, whereas the liberation of As was related to adsorption by iron hydroxide.