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Mining and smelting releases toxic contaminants such as zinc (Zn), lead (Pb) or cadmium (Cd) into the soil thereby poisoning it and rendering it unproductive. Remotely alternatives have been widely employed in the attempt of estimating heavy metal content within soils. The present study provides a methodological approach based on VNIR-SWIR field hyperspectral data and multispectral Landsat OLI 8 imageries for the prediction and mapping of Pb, Zn and Cd heavy metal contents around the abandoned Jebel Ressas mine site in Northern Tunisia. Thus, eighty-seven soil and tailing samples were collected from the study site and VNIR-SWIR field reflectances were measured on the same collection points, as well. All samples were analysed by atomic absorption for the estimation of heavy metal concentrations. The partial least squares regression PLSR was conducted considering the measured heavy metal concentrations and using multi-scale data: VNIR-SWIR field hyperspectral data and multispectral Landsat OLI 8 imagery. Standard normal variable (SNV) and multiple scatter correction (MSC) preprocessing methods were applied for further mapping improvement. Thus, this work aims to automate the estimation of the heavy metal contents in contaminated soils, by carrying out: a modeling approach based on the PLSR using VNIR-SWIR field hyperspectral data, ii) the mapping of Pb and Zn contents thanks to the exploitation of Landsat OLI8 multispectral imagery and iii) the application of both MSC and SNV preprocessing methods to optimize the performance of the developed models, when using such spectrally and spatially degraded data.

International audience; Mine tailings, left after the mine activities without any control, are charged of heavy metals and contaminating minerals, qualified as risks minerals. In this study, we explore the potential of hyperspectral field spectroscopy in predicting the abundance of risk minerals in agricultural soils around the Hammam Zriba mine site in Northern Tunisia. Sixty-nine samples were gathered from the top surface of soils and dikes (tailing deposits) and measured using the ASD Field Spec HiRes operated in VNIR/SWIR regions (350-2500 nm). All samples were analyzed by X-ray diffraction method XRD for the estimation of both several minerals, including Barite and Fluorite contents. The partial least squares regression (PLSR) was used to relate the measured VNIR/SWIR spectra to XRD analysis results for the prediction of risk mineral contents. The prediction performances of Fluorite and Barite contents were evaluated using particularly, the coefficient of determination R2 and the ratio of performance to deviation RPD. Results have shown an accurate prediction of both risk minerals using VNIR/SWIR hyperspectral field spectroscopy

Mining in Tunisia generates a large amount of tailings charged with toxic minerals. As these tailings have a wide spread distribution, it is important to characterize and estimate their impact on soil contamination. This study examines the potential of field hyperspectral spectroscopy and SENTINEL-2 Multispectral data in estimating and mapping seven minerals content, including three toxic minerals (fluorite, barite and sphalerite), within soils around Hammam Zriba mine in Northen Tunisia. 69 soil and dike surface samples were collected, field Visible, Near InfraRed (VNIR) and Short-Wave InfraRed (SWIR) reflectance spectra were measured on these surfaces. The X-ray diffraction (XRD) method was used to identify the types of mineral and their associated contents on each collected soil samples. The mineral contents were predicted using the partial least squares regression (PLSR) method using i) field VNIR-SWIR spectra at raw spectral resolution, ii) field VNIR-SWIR spectra aggregated to the SENTINEL-2 spectral resolution and then iii) SENTINEL-2 spectra. This study shows 1) an accurate prediction of four of the seven minerals using field VNIR-SWIR spectroscopy, 2) a slight decrease of performances due to spectral resolution degradation (SENTINEL-2 simulated spectra) and 3) a significant decrease of performances due to spatial resolution degradation, except for fluorite. This work paves the way for large-scale mapping of minerals with high pollution potential using SENTINEL-2 data. In addition, the high frequency of SENTINEL-2 data may be used to monitor the spatial distribution of some minerals with high pollution potential in soils.

Mine wastes of the abandoned Pb-Zn mining district of Jebel Hallouf-Bouaouane in the north of Tunisia are continually exposed to erosion and thus threaten soils, vegetation and above all human health. Detecting changes of mine wastes in a quick and timely fashion is the first step towards mitigating their impact and surveying the environment. Thus, this study shows the role and importance of earth observation technology and a type of spatial science processing in mine waste change detection and assessment. Both pre- and post-classification methods based on multitemporal and multisensory Landsat ETM+ and OLI 8 data are performed and compared to evaluate the efficiency of the methods. Field measurements, X-ray diffraction (XRD) analysis of field samples and polished section observations were used to evaluate waste changes identified remotely. The comparison of results shows that the pixel-based iteratively reweighted multivariate alteration detection (IR-MAD) pre-classification method offers the bes...

En Tunisie orientale, le système conjugué de Gotaia et Eliane dans la région de Mahdia est formé par deux dépressions continentales en forme de huit. Les dépôts sédimentaires illustrent deux phases de sédimentation. Le premier est un dépôt sableux caractérisé par des sables fins, modérément classés et déposés selon l'emplacement des points d'échantillonnage essentiellement par excès de charge. La deuxième phase est marquée par des sédiments plus riches en fraction fine correspondant à une période d'envasement. L'étude de l'environnement sédimentaire des deux sebkhas a montré que les matériaux détritiques sont d'origine continentale. L'étude minéralogique révèle une particularité de ces systèmes s’illustrant par un dépôt de gypse en zone centrale et l'absence de halite. Le gypse n'est pas présent en croûte mais détecté par diffractométrie aux rayons X en pourcentage assez important dans les sédiments. A sedimentary deposit in the conjugated system of Gotaia and Eliane situated in Eastern Tunisia in the region of Mahdia illustrates two phases of sedimentation. The first part is composed by sandy deposit characterized by fine grain, moderately sized and filled by excess load. The second is a siltation phase and is marked by the abundance of clay sediment. The sedimentology and mineralogy studies show that detrital materials have continental origin. The particularity of this system is the presence of gypsum only in the central zone. Gypsum is not present in the crust, but detected by X-ray diffractometry with large percentage in sediments.

The present work is based on The RYSCMED project supported by PHC-UTIQUE 2016-2018 (16G 1005 –34854QC). The RYSCMED is an interdisciplinary project which gathers different disciplines (e.g. sedimentology, hydrology, geochemistry, ecology, paleontology, biochemistry, archeology) to quantify the sediment flow of the land-sea. This research aims at identifying coastal sediment dynamics (via the sand supply sources; i.e. Medjerda River) and hydrodynamic parameters to understand the local environmental problems in an urbanized coastal framework. The outcome is expected to produce original and new findings about the link between dams, river hydrology and sediment origin to the sea, with the impact of climate and anthropogenic activities on the coastal geomorphology and ecosystem sensitivity. The main scientific outcome will be addressed to the socio-economic actors to implement necessary solutions for remediating the Mediterranean coastal vulnerability. (Abstract author)

Owing to the inaccessibility of most of the mineral deposits as well as cost and time requirements for conventional ground-based methods, remote sensing techniques become very useful for the rapid detection, mapping, and multitemporal tracking of different mineralization surface states. In this context, a methodological approach based on hyperspectral spectroscopy and Advanced Spaceborne Thermal Emission and Reflection (ASTER) data is proposed for the phosphate exploration and mapping in a specific geological context in Tunisia. ASTER’s thermal infrared (TIR) portion has been particularly expedited in phosphate detection and mapping. Visible near-infrared (VNIR), shortwave infrared (SWIR), and TIR atmospherically and geometrically corrected data are thus processed using the matched filtering (MF) method and VNIR-SWIR reflectance spectra of the collected samples. Results revealed that different absorption features of carbonate minerals (calcite and dolomite) in the SWIR region have to be considered for an efficient identification of rock phosphate. Proposed band combinations using MF fraction maps have successfully discriminated phosphate mineralization and outcrops. Moreover, the surface temperature map derived from TIR bands using the emissivity normalization method reveals the usefulness of the proposed method for rock phosphate delineation. Both geological map and published prospects map as well as x-ray diffraction (XRD) analysis results are used for the validation purposes. A high kappa coefficient value of 0.92, 0.97, and 0.88, is thus calculated, respectively, for VNIR, SWIR, and TIR data-based maps. The high kappa coefficient values implicate the contribution of proposed methodological approach in exploration and mapping phosphates in the Chaketma mine site in central west Tunisia.

Hammam Zriba district mine (36°20′N and 10°13.5′E) which includes the Tunisian fluoric province (F-Ba-Zn-Pb) is among the most important one in the Maghreb. The important waste quantities which were left over after smelting have a wide spread distribution without any control. Particularly, the residues of lead zinc and above all fluorine and barium cause the environment degradation and threaten the human health. Reflectance spectroscopy provides information about minerals and heavy minerals present within wastes, between visible (VIS) and shortwave infrared (SWIR). In this study, we propose an approach based on VNIR and SWIR reflectance spectroscopy with respect to XRD laboratory analysis. Particularly, we are interested on the content estimation of risk minerals through linear modeling using proposed hyperspectral parameters. The selection of all parameters is based on the continuum removal method. Regression results show that our proposed approach for the prediction of risk minerals is efficient.

Proceedings of Euro-Mediterranean Conference for Environmental Integration (EMCEI-1), Tunisia 2017; A great number of rivers of North Africa are equipped with many dams for multiple purposes, mainly potable water, irrigation and energy production. In most of the countries—Morocco, Algeria and Tunisia, the storage capacity exceeds the runoff capacity, which means that water is stored several times in a row during its course to the sea.

Over several decades, the mouth of the Mejerda River (northern Tunisia) has received large amounts of mining tailings mainly containing Pb, Zn and Ba. We have measured the concentrations of major and trace elements (Al, Ti, P, K, Mg, Na, Ca, S, Fe, Cl, V, Cr, Co, Ni, Cu, Zn, Ga, Br, Rb, Sr, Y, Zr, Nb, I, Ba and Pb) in three different fractions of 45 surficial sediments using wavelength dispersive X-ray fluorescence. The size distribution of fine particles (

Superficial sediments were collected from the Mejerda River delta between October and November 2008. Samples were analysed for 15 trace and major elements (Cd, Pb, Zn, Mn, Ni, Co, Cr, Cu, Sr, Fe, Al, Ca, Mg, Na, and K). Fine fractions, carbonates, total organic carbon, minerals and acid volatile sulfide (AVS) were also analysed to explain the spatial distributions of heavy metals.There are two theories of metal spatial distribution: metals concentrated in coastal sediments (Ca, Mn, and Sr) and metals concentrated in offshore sediments (Al, Fe, Mg, Na, K, Pb, Zn, Cr, Co, Ni). Ca, Mn and Sr show similar distributions to those of carbonates, quartz and calcite; these elements show their greatest concentrations in the coastal sediments. However, Al, Fe, Pb, Zn, Cr, Co and Ni show a large concentration in offshore sediments, such as in the clay and silts (< 20μm). None of these metals has a visible affinity with the organic carbon or AVS, indicating that the carbonates and fine fraction are the essenti...

Hyperspectral measurements were carried out at tree canopy as well as leaf levels in an olive field around the Jebel Ressas mine site using the ASD (350 – 2500 nm) instrument. The main objective of this study was to explore hyperspectral reflectance spectroscopy to detect heavy metal vegetation stress as an indicator of soil contamination. Moreover, the used families of Vegetation Indices were optimized and tested. The results indicated that vegetation indices based on the near infrared shortwave infrared (NIR - SWIR) domain can be obtained at tree canopy and leaf levels. At leaf level, a good detection of heavy metal vegetation stress was showed using optimized indices.

Dispersion of metal rich particles from mine tailings is an important hazard for the environment. Specially, in Mediterranean context, this is potentially more risky because of the violence of climatic events. Northern Tunisia includes about 50 mining districts with an ore mineralogy consisting mainly of galena, iron sulphides and subordinate sphalerite embedded in a calcitic and baritic gangue. A century of mining exploitation left waste rich in potentially toxic elements (PTE) with values up to 46900 mg/kg for Pb and 49501 mg/kg for Zn, stored in uncontrolled and untreated deposits. The PTE contents observed in the surrounding soils generally devoted to agricultural activities are as high as 12488 mg/kg for Pb, 3485 mg/kg for Zn and 15 mg/kg for Cd. The contents in sediments downstream are also high, in the range of 47800 mg/kg for Pb, 5767 mg/kg for Zn and 36 mg/kg for Cd. PTE-bearing phases are mainly sulphides, carbonates and iron oxyhydroxydes. Because of the lack of vegetation and the presence of fine particles in the mining wastes, PTE were dispersed to nearby areas, resulting in the contamination of agricultural soils and river sediments. Under the Mediterranean climate which includes a long dry summer with windy episodes and heavy rainfall in the winter, mine tailings are exposed to two types of erosion: hydraulic erosion with transport during heavy rainfall events and aeolian erosion inducing fine particle dispersion. Dispersion of the PTE from mine tailings in northern Tunisia presents a risk of environmental contamination and of toxicity by inhalation for the habitants near the former mining districts. Furthermore these PTE can be transferred from agricultural soils surrounding the tailings to the cultivated plants (mainly cereals).

Three cores were collected in the lagoon of Ghar El Melh (Northern Tunisia) and the sediments were analysed for trace and major elements, sulfides acid volatile sulfides (AVS) and pyrite and total organic carbon (TOC). The sediments are composed of black-mud in the upper layer (0–10cm depth) and grey-mud underneath. Based on the lagoon history, it was believed that the black-mud is endogenic, while the grey-mud is exogenic (derived from old contributions of the Mejerda River before its diversion). The concentrations of TOC and AVS decrease with depth, while the redox potential (Eh) is negative in the black-mud and positive in the grey-mud. The Eh measurements thus revealed the singularity of the sedimentation mode in this lagoon. The North American Composite Shale (NASC) normalisation indicated that Cd, Zn and Pb were enriched through the entire profiles, indicating that this sediment was contaminated for a long time by mining activities and human pollution. Trace metal profiles of Fe, Cd, and Cu ...

Abandoned mines cause critical problems which are among the most challenging environmental ones. This is the case in Tunisia, were effects of mining activity are well illustrated particularly in Mejerda and Mellag river watersheds. Mapping is the first step for the inventory, characterization and survey of mine wastes elsewhere. Particularly, detecting changes in images of the same scene taken at different time series is of special interest in this application domain. In this context, we applied a based MAD (Multivariate Alteration Detection) transformation method for multi temporal classification and change detection of mine wastes. For these purposes we used Landsat ETM+ time-series data.

Detailed investigations in the western part of the “zone des nappes” in the Tunisian Atlas enable to propose an original model for this area. We show that, according to sedimentary records, these units appear to be formed by various series originally deposited on tilted crustal blocks of the North African margin. This south-easternward tilting occurred from the Triasic to the early Miocene. The first phase of inversion took place during the early to middle Miocene interval; no older compressive event can be highlighted. The shortening is associated with a system of flats and ramps thrust faults that occurs following a piggy-back sequence and that does not disrupt the paleogeographic order. Subsequently, an “out-of-sequence” event places the upper unit (Numidian Unit) onto the sub-numidian Units. The overlap length remains very moderate betwen sub-numidian Units (a few kilometers only). Finally, during the late Quaternary, the area undergoes a late shortening that folds the syn-tectonic basins.

This paper presents mineralogical and geochemical data from several continental sequences located in Central (Ain Ghrewiss and Kebar) and Central-Southern Tunisia (Selja, Kef Schefeir, Shib, Oum El Kcheb and Haidoudi). These sequences vary in age from Late Palaeocene to Early Oligocene and contain considerable quantities of fibrous clays (up to 75% palygorskite and 90% sepiolite). These clays appear in assocation with carbonates (mainly dolomite), detrital aluminosilicates (illite, Al smectites, mixed-layers illite–smectite and kaolinite), quartz and lesser quantities of gypsum and halite. The textural characteristics observed by electron microscopy, the trace and rare earth elements contents and their distribution in the various mineral phases, together with the isotopic composition of dolomite and fibrous clays, provide good clues as to the genesis of the neoformed minerals. Thus, the sepiolite would have precipitated directly in lacustrine, playa-lake or sebka environments under alkaline conditions, high Si and Mg and low Al activity, and arid to semiarid climate. On the other hand, the palygorskite would have formed by transformation of already existing illite and/or smectite type aluminosilicates in solutions in equilibrium with isotopically heavier and, therefore, more evaporated solutions than the sepiolite.

Field spectral data, measured on the ground by a spectroradiometer are very important and needed for tailing classification. The Spectral Modeling Approach SMA based on library reflectance's fusion is an optimal solution in absence of field data. In this study, we give a generalization of the approach we developed in [5]; [6] for other types of mine in Tunisia. The main contribution is to estimate the tailing components' spectral reflectance by direct means. This allows us to replace the lack of the field data needed for mine tailing mapping. Thus, we can generate tailing maps from multispectral data particularly those acquired in the previous date. The results indicate that SMA can be applied successfully.

The Southern part of the Gulf of Gabes, SE of Tunisia, is a microtidal sandy coast. It is recently developing a series of sand spits. We seek to determine the evolution of the coast over the past decades and to establish the hydrodynamic conditions that led to this development. To do this, we relied on the diachronic study of the shoreline from aerial photographs from 1985 and 1997. Thus, the evolution of the coast is subject to continuous changes that reflect an active sediment dynamics. Keywords- Littoral drift, morphological evolution, sandy coast, sediment dynamics, spits.