Incurred environmental risks and potential contamination sources in an abandoned mine site

The mineralogical characterization of Fedj Lahdoum mine wastes measured by X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) showed the presence of the following sulfide minerals: galena (PbS), sphalerite (ZnS), pyrite (FeS2), cerussite (PbCO3) and smithsonite (ZnCO3). The wastes were stored in tailing ponds. The results showed that the concentration of metals from tailings were up to 10 460 mg.kg-1 for total Zn, 2 100 mg.kg-1 for total Pb and 62.08 mg.kg-1 for total Cd. The tailings have presented a fine unconsolidated texture that accelerated the dispersion of the particles rich in heavy metals. Geochemical analysis of soil has revealed high total contents of Pb, Zn and Cd, respectively: 3 646, 3 236 and 17 mg.kg-1. Chemical analysis of cultivated and wild plants species inside the district contain high grades in heavy metals: 708.56 mg Zn. kg-1; 16.24 mg Pb.kg-1 (Thymus vulgaris (L)); 500.44 mg Zn. kg-1, 12.44 mg Pb. kg-1 (Laurus nobilis (L)); 128.33 mg Zn. kg-1 and 22.53 mg Pb.kg-1 (Ficus (L)) and 106.73 mgZn.kg-1 (pimento). The high levels detected in soil and plants have exceeded the Tunisian and Canadian standards. These results showed that the abandoned site was contaminated by the presence of tailing dumps which were exposed to significant water and/or wind erosion. To solve this problem, we proposed an environmental desulphurization by froth flotation.Keywords: Heavy metals, mine tailings, abandoned mining-district, plant contamination

Les Algues Indicatrices De L'eutrophisation Et De La Contamination De La Lagune De Korba (Cap Bon Tunisie)

The concentrations of heavy metals (Fe, Zn, Pb and Mn) were determined in two green algae (Enteromorpha intestinalis and Chaetomorpha Linium) collected from April 2012 to February 2013 in nine stations characterized by the abundance of these algae throughout the year. Determination of Pb, Mn and Zn was carried out by graphite furnace atomic absorption spectrometer while Fe by flame atomic absorption spectrometer (using the Thermo Scientific ICE 3300 AA Spectrometer). An evaluation of the degree of eutrophication is made through the physicochemical study of 31 samples in the surface water. The results underline that Korba is an eutrophic lagoon. The heavy metal concentrations in the water samples decreased in the sequence of Fe >Zn > Mn > Pb, while in Chaetomorpha Linium, Enteromorpha intestinalis and sediment exhibited the same pattern across the sites: Fe >Mn> Zn >Pb. The results show that metal accumulation capacity in both macro-algae varies according to the season and depends on the species. By comparison with other studies in the world, the levels found in the algae of Korba lagoon are relatively high except Mn. Chaetomorpha Linium could be used as an excellent indicator for heavy metals accumulation in Korba lagoon

Genetic differentiation of Yemeni people according to rhesus and Gm polymorphisms

For introducing Yemeni population in synthesis of genetic relationships of human populations, analysis of rhesus and Gm polymorphisms have been carried out for a population sample of 210 Yemenites. Rhesus haplotype frequencies were compared to those estimated in an original sample of 171 Tunisians and to available data for other populations. Gm haplotype frequencies were introduced in a wide synthesis of genetic relationships for 67 populations from Africa, Europe, the Near East and India. The genetic profile of Yemeni people would be close to that of a highly diversified ancestral population. The first inhabitants of North Africa, the Berbers and Yemenites have very likely a common origin and were not subject to important genetic drift after their geographic differentiation. While, the divergence between Yemenites and their neighbours of sub-Saharan Africa would have occurred with a founder effect and a long isolation. An important parallelism is observed for the Gm system between genetic and linguistic differentiations

Mineralogical and geochemical signatures of clays associated with rhyodacites in the Nefza area (northern Tunisia)

International audienceThe geology of northern Tunisia is marked by magmatic extrusion that occurred during the Middle Miocene (Langhian-Lower Tortonian), which led to the outcrops of rhyodacites in the Nefza-Tabarka region. This event is contemporaneous with the Alpine compressional phase, which is well-characterised in the western Mediterranean area, where intense fracturing and hydrothermalism occurred with evidence of metallogenic consequences. In this paper, a detailed study is presented on the acid volcanic rocks that outcrop at the core of the Oued Belif structure in the Nefza area of northern Tunisia. The results indicate that these series have undergone various transformations subsequent to their extrusion. These alterations include ferrugination, silicification, argilitisation and devitrification of volcanic glass. Petrographic observations demonstrated that the primary minerals, particularly feldspars, biotite and mesostasis glass, were affected by hydrothermal and meteoric weathering. The mineralogical study of the neogenic products revealed a nearly monomineral smectitic phase with relatively low levels of added illite and/or kaolinite. These neoformed smectites were classified as ferroan beidellites-nontronite based on thermal and crystallochemical analyses. Chemical analysis of the major elements, trace elements and rare Earth elements (REEs) show the presence of Al, Fe and K and an enrichment of REE in the clay fraction with a greater fractionation of light rare Earth elements (LREEs) compared with that of heavy rare Earth elements (HREEs). The abundance of these elements is attributed to their mobility during chemical weathering of acidic lavas and their adsorption by clay mineral

Sulfur Speciation of Crude Oils by Partial Least Squares Regression Modeling of Their Infrared Spectra

Research has been carried out to determine the feasibility of partial least-squares regression (PLS) modeling of infrared (IR) spectra of crude oils as a tool for fast sulfur speciation. The study is a continuation of a previously developed method to predict long and short residue properties of crude oils from IR and near-infrared (NIR) spectra. Retention data of two-dimensional gas chromatography (GC GC) of 47 crude oil samples have been used as input for modeling the corresponding IR spectra. A total of 10 different PLS prediction models have been built: 1 for the total sulfur content and 9 for the sulfur compound classes (1) sulfides, thiols, disulfides, and thiophenes, (2) aryl-sulfides, (3) benzothiophenes, (4) naphthenic-benzothiophenes, (5) dibenzothiophenes, (6) naphthenic-dibenzothiophenes, (7) benzonaphthothiophenes, (8) naphthenic-benzo-naphthothiophenes, and (9) dinaphthothiophenes. Research was carried out on a set of 47 IR spectra of which 28 were selected for calibration by means of a principal component analysis. The remaining 19 spectra were used as a test set to validate the PLS regression models. The results confirm the conclusion from previous studies that PLS modeling of IR spectra to predict the total sulfur concentration of a crude oil is a valuable alternative for the commonly applied physicochemical ASTM method D2622. Besides, the concentration of dibenzothiophenes and three different benzothiophene classes can be predicted with reasonable accuracy. The corresponding models offer a valuable tool for quick on-site screening on these compounds, which are potentially harmful for production plants. The models for the remaining sulfur compound classes are insufficiently accurate to be used as a method for detailed sulfur speciation of crude oils

Paleocene–Eocene palaeoenvironmental conditions of the main phosphorite deposits (Chouabine Formation) in the Gafsa Basin, Tunisia

A detailed sedimentary section of the marine Chouabine Formation in the palaeogeographic Gafsa Basin, south-western Tunisia, was investigated in order to characterize environmental and depositional conditions focusing on the interval that spans the Paleocene–Eocene transition. We did stable isotope analyses of bulk sediments. Both phosphorite and carbonate yielded relatively similar isotopic compositions; while marls show observable trends, with negative shifts in both δ13Cinorg and δ18O values at the Paleocene–Eocene transition. The diversity of the calcareous microfossils is low. The presence of few environmentally tolerant small benthic foraminifera and the absence of planktic forms indicate a restricted palaeoenvironment subject to variation in salinity and temperature. The ostracod fauna is more diverse and is rather comparable to Paleocene and PETM (Paleocene–Eocene thermal maximum) assemblages in northwest Tunisia. While all these microfossils demonstrate various diagenetic features (i.e., phosphatization, secondary mineral overgrowths and infills), the different groups retain distinct stable isotopic compositions, suggesting partial preservation of signatures derived from their respective ecological niches. Few organic-rich layers below the negative δ13C shift yielded dinoflagellate assemblages with the common forms of Adnatosphaeridium sp., Operculodinium sp., Spiniferites spp. and Thalassiphora sp. The rare presences of Apectodinium-complex agree with depositional age prior to the PETM. The combined data emphasize that most of the Chouabine Formation in the Gafsa Basin was deposited during the late Paleocene. The most negative isotopic values from marls are believed to represent the onset of PETM or pre-PETM record, and the related perturbation of the carbon cycle in shallow water deposits in Tunisia