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This study aims to evaluate the impact of the former mining Touiref district (NW Tunisia) on the spatial distribution of metal contamination. In order to characterize the metal content of the tailings and to assess how far the soils from the district could be impacted by metals, a sampling campaign was conducted. According to the spatial distribution concentration maps of potential toxic elements (PTE), the highest concentrations occur near the flotation tailings and in mining facilities and decrease abruptly with distance. These results confirm that wind is the main agent capable of dispersing metals in a W-E direction, with concentrations exceeding the standards of soil quality for Cd, Pb and Zn over several hundred metres away from the source, facilitated by the small-size fraction and low cohesion of tailings particles. Chemical fractionation showed that Pb and Cd were mainly associated with the acid-soluble fraction (carbonates) and Fe-(oxy) hydroxides, while Zn was mainly associated with Fe-(oxy) hydroxides but also with sulphides. Thus, the immobilization of metals in solution may be favoured by the alkaline conditions, promoted by carbonates dissolution. However, being carbonate important-bearing phases of Cd and Pb (but also for Zn), the dissolution facility of these minerals may enhance the release of metals, particularly far away from the mine where the physicochemical conditions can be different. Also, the metal uptake by plants in these alkaline conditions may be favoured, especially if secondary phases with high sorption ability are reduced at this site. A remediation plan to this area is needed, with particularly attention in the confinement of the tailings.

ABSTRACT:The aim of this research is to detect the neotectonic activity and to map the seismic risk potential in the plain of Kasserine using the longitudinal profile of the Htab River and its tributaries. The adapted methodological approach is based on the extraction of the longitudinal profile and knickpoints, which are the main source of seismicity information in a plain filled up with more than 1000 m of silty deposit. In such a plain, compact structures are absent and thus we cannot detect the ordinary tectonic indices. The selected longitudinal profiles of the tributaries of the Htab River, extracted along the plain, show normal forms like river 1, 12 and 14 and abnormal ones such as 3, 5 and 7. The knickpoints distribution shows two main alignments trending NW-SE. The first one is in Semmama Mountain and it is represented in the structural map of Kasserine whereas, the second one is located in the plain of Kasserine and we think that it is caused by neotectonic activity. To confirm this hypothesis we use seismic records of the National Meteorology Institute since 2000. These data show seismic activity in the plain which is also a witness of a NW-SE alignment. Moreover, in situ investigations are performed and results pinpoint normal fault activity in the plain. Knickpoints, seismic records, and in situ investigation emphasize significant neotectonic activity affecting the thick quaternary plain of Kasserine.

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This article endeavours to analyse the recent deformation in the Enfidha region. This analysis has been carried out using the Residual Digital Elevation Model (DEM). It is the altimetric difference between two DEM generated from the contour lines of two topographical maps over a period of 100 years.