Abstract
In this study, the sequential extraction method was applied to extract selected potentially toxic elements (PTEs) (Cd, Cr, Cu, Fe, Ni, Pb and Zn) in river sediments collected from the Blood River situated in Seshego area, Limpopo Province, South Africa. The study aimed to assess a possible trend of mobilisation of these elements from sediment to water. The accuracy of the sequential extraction method was confirmed by analysing sediment-certified reference material, and quantitative percentage recoveries ranging from 86 to 119%, 81 to 111% and 77 to 119% were achieved for exchangeable, reducible and oxidisable fractions, respectively. The potential risk of the PTEs in sediments was evaluated. The calculated values of contamination factor (CF) as well as risk assessment code (RAC) for Cd, Cu, Ni and Pb revealed the mobility of these elements. The PTEs in river sediments are at a high toxicity-risk level and could therefore cause a threat to organisms dwelling in sediments and humans via consumption of crops irrigated with the polluted river water.
Highlights
Toxic elements (PTEs) are known to be adsorbed directly to the sediments of the water system
Iron in sediment samples was quantified by flame-atomic absorption spectrometry (F-AAS), and its limit of detection (LOD) and limit of quantification (LOQ) values were 0.049 mg·kg−1 and
Sequential extraction of Cd, Cr, Cu, Fe, Ni, Pb and Zn in river sediments was achieved by employing the BCR sequential extraction procedure
Summary
Toxic elements (PTEs) are known to be adsorbed directly to the sediments of the water system. Some of these elements may not be permanently bound by the sediments. The risks associated with sediments contaminated by PTEs strongly relate to their specific chemical fractions and binding states. Factors such as the sediments’ nature, grain size, and properties of adsorbed particles as well as of the element could influence the mobility of PTEs in sediments [3]. Fractionation of PTEs in sediments by sequential extraction is helpful to understand their source, mode of occurrence, mobility and bioavailability [5]
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