SPECIATION AND MOBILITY OF LEAD AND ZINC IN SOME CONTAMINATED SOILS OF EGYPT | ||||
| Journal of Soil Sciences and Agricultural Engineering | ||||
| Article 6, Volume 5, Issue 6, June 2014, Page 817-830 PDF (808.4 K) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/jssae.2014.49557 | ||||
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| Author | ||||
| M. A. Abd El - Aziz | ||||
| Soil, Water and Environment Research Institute,Agric. Res. Centre, Giza, Egypt | ||||
| Abstract | ||||
| Heavy and trace elements are potentially toxic to human life and the environment. Element toxicity depends on chemical associations in soils. Therefore, determining the chemical form of an element in soils is important to evaluate its mobility and bioavailability. In this study, three polluted soil profiles representing the most predominant soil types (ie, clayey, calcareous and sandy soils) of Egypt were investigated for the distribution and chemical fractions of Pb and Zn and their mobility in relation to soil properties. Sequential extraction was used to fractionate Pb and Zn into six operationally defined groups: water soluble (F1), exchangeable (F2), carbonate (F3), Fe-Mn oxide (F4), organic (F5) and residual (F6). This sequential extraction procedure is based on operationally defined mobile (F1 to F3) and immobile (F4 to F6). The obtained results indicated that the residual fraction was the dominant pool for the studied elements examined in the different soils, and accordingly the potential availability of these studied elements was extremely low. In contaminated clay soil, Pb and Zn were mostly concentrated in the residual and oxide-bound fractions, while in contaminated calcareous soil the Pb and Zn was mostly concentrated in the residual and carbonate-bound fractions. In contaminated sandy soil, Pb and Zn bound to organic matter was the dominant fraction where Pb and Zn distribution pattern followed the order: organic-bound> residual> oxides-bound> carbonate-bound> exchangeable> water soluble fractions. The values of mobility factor (MF = [sum (F1 to F3) x 100/sum F1 to F6)] showed that Zn is more mobile than Pb metal in the studied soils. Therefore, Zn is likely to be easily taken up by vegetation grown in these contaminated soils. For Pb and Zn the MF values were highest (19.20 – 22.24%, respectively) in contaminated clay soil and lowest (7.43 – 9.71%) in sandy soil, while intermediate (13.58 – 18.06%, respectively) in calcareous soil. The correlation of Pb and Zn forms with some soil properties showed that soil organic matter content and pH were the most important factors controlling Pb and Zn distribution and subsequently, its bioavailability in contaminated clay and calcareous soils, while in contaminated sandy soil, the most effective soil properties on Pb and Zn speciation were organic matter and clay contents followed by soil pH. | ||||
| Keywords | ||||
| Heavy metals; Pb; Zn; speciation; sewage effluents and soil properties | ||||
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