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Hazardous elements speciation in sandy, alkaline coal mine overburden by using different sequential extraction procedures

Posted on 4. June, 2014.

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Worldwide surface coal exploitation has made an impact on the environment by producing massive overburden stock piles with very heterogeneous physico-geochemical properties.

The restoration of such soils is usually associated with the complex problem of overburden such as bad physical properties and low fertility, especially if the humus topsoil layer has not been preserved during the coal excavation. The problem of overburden soil restoration is very often associated with increased accumulation of hazardous elements from subsoil layers.

This paper deals with the problem of hazardous elements (HE) speciation in sandy, alkaline coal mine overburden destined for restoration. Two sequential extraction procedures [five stages Tesier’s (T) and seven stages Zeien and Brümmner’s method (ZB)] were employed that focused on potentially bioavailable HE fractions previously found in plants growing during this soil restoration process. The results showed that the selection of the extraction procedure in HE speciation is essential, due to the different potential threats of HE fractions obtained for plants. The biggest residual fraction obtained by both extractions suggest geogenic origin of Cu, Zn, Ni, Cr and Pb. Tesier’s extraction procedure works reasonably well for low concentration of water soluble and exchangeable HEs, whilst giving higher values for their organically bound forms. Zeien and Brümmner’s method, however, was found to be more appropriate for evaluation of the mobility of HE as Mn and Fe oxide fractions. The principal component analysis test estimated three main groups where the relationship between soil properties (pH, clay and silt), total content of element and available fractions (Zn, Ni, Cr, Pb-T and Ni-ZB) was defined as a PC 1 group. 
Other PC 2 and PC 3 from the PCA analysis include Corg and CEC, and available Cu-T and Cr, Pb-ZB, respectively. The PC 3 factor linked fine sand and available Zn-ZB. Pearson’s correlation coefficients showed a high correlation between available HE and high pH(KCl) obtained by T-extraction, and Ni by Zn-extraction. Also, clay, silt and fine sand were highly correlated with the Ni-ZB available forms.

Keywords: overburden, hazardous elements, sequential extraction procedures, principal component analysis

Authors: Ivana Trajković, Vlado Ličinaa, Svetlana Antić-Mladenović and Walter Wenzel


Read the complete article in Chemical Speciation & Bioavailability,  Volume 26, Number 2, April 2014, pp. 85-91

Image courtesy of: Alexey Zaytsev /