Fingerprinting vanadium in soils based on speciation characteristics and isotope compositions

Abstract

Vanadium (V) can have toxic effects on human organs and physiological systems, yet tracing V sources remains challenging. Here, two methods were used for V source tracing in soil based on speciation characteristics and isotope compositions. According to the sequential extraction method of the European Communities Bureau of Reference (BCR), the analysis of speciation distributions offers a possible means of distinguishing V sources. Here, the isotope compositions of polluted soils around a coal-fired power plant and smelter in China were used to identify the sources of V. Significant V isotope variation (δ⁵¹V range = -0.74 ± 0.07; mean ± 2SD = -0.52 ± 0.05‰) was observed in the soil samples, attributed to coal-burning (Δ⁵¹V_{Coal-Fly ash 1} = -0.31 ± 0.05‰; mean ± 2SD; n = 1) and smelting processes (Δ⁵¹V_{Slag-Fly ash 2} = -0.31 ± 0.07‰; mean ± 2SD; n = 1). All of the soil V isotope ratios plotted within the range of end-member components corresponding to potential V contributors in the environment. Among these, δ⁵¹V ranged from -0.74 ± 0.07 to -0.55 ± 0.02‰ in topsoil, the average δ⁵¹V was -0.52 ± 0.05‰ in the deep soils, and the δ⁵¹V of the end-member components ranged from -0.52 ± 0.05 to -0.94 ± 0.11‰. The primary anthropogenic source of V in the topsoil was fly ash from coal-burning that was consistent with the BCR method results. Furthermore, the downward migration of V was identified in the soil profile adjacent to the smelting plant, and V in the deep soils was dominated by natural sources relative to anthropogenic sources in the surface soils.

Keywords: Non-traditional stable isotopes; Soil; Source tracing; Speciation; Vanadium.