Hydrochemistry and stable isotopes (δ 18 O and δ 2 H) tools applied to the study of karst aquifers in Southern Mediterranean basin (Teboursouk area, NW Tunisia)

Karst aquifers receive increasing attention in Mediterranean countries as they provide large supplies water used for drinkable and irrigation purposes as well as for electricity production. In Teboursouk basin, Northwestern Tunisia, characterized by a typical karst landscape, the water hosted in the carbonates aquifers provides large parts of water supply for drinkable water and agriculture purposes. Groundwater circulation in karst aquifers is characterized by short residence time and low water-rock interaction caused by high karstification processes in the study area. Ion exchange process, rock dissolution and rainfall infiltration are the principal factors of water mineralization and spatial distribution of groundwater chemistry. The present work attempted to study karstic groundwater in Teboursouk region using hydrochemistry and stable isotopes (δ18O and δ2H) tools. Karst aquifers have good water quality with low salinity levels expressed by TDS values largely below 1.5 g/l with Ca-SO4-Cl water type prevailing in the study area. The aquifers have been recharged by rainfall originating from a mixture of Atlantic and Mediterranean vapor masses

Bioaccessibility of potentially toxic metals in soil, sediments and tailings from a north Africa phosphate-mining area: Insight into human health risk assessment

The risk assessment of phosphate mining/processing industrial activities on the environment and human health is crucial to properly manage and minimize the risks over time. In this work, we studied the inhalation and dermal bioaccessibility of potentially toxic metals (PTM) in different particle-size fractions of urban soil, sedi- ments and tailings from Gafsa-Metlaoui phosphate mining area, to assess afterwards the non-carcinogenic (NCR) and carcinogenic (CR) risks for the health of local citizens and workers constantly exposed to airborne particulate matter (PM) originating from these sources of contamination. Samples were separated in particle-size fractions by centrifugation and consecutive cycles of sedimentation and decanting. The pseudo-total concentrations and bioaccessible fractions of PTM were extracted by aqua regia and in vitro bioaccessibility tests, respectively. Both sediments and tailings showed higher-than-background concentrations of PTM (mainly Cd, Zn and Cr), with a tendency to accumulate these metals in fine particles (1 and CR > 10− 4), especially for children, can occur if ingestion route is also considered. The findings underline the need for adequate protection of contaminated soil, sediments and mine tailings laying nearby urban agglomerates, to reduce the health risks for inhabitants and workers of Gafsa-Metlaoui mining area

Evaluation of potentially toxic elements' (PTEs) vertical distribution in sediments of Gafsa-Metlaoui mining basin (Southwestern Tunisia) using geochemical and multivariate statistical analysis approaches

The present study represents a preliminary geochemical investigation concerning the vertical distribution of potentially toxic elements (PTEs) in the sediments of an industrial site in Gafsa-Metlaoui mining basin of phosphate using multivariate statistical analysis. It attempts to outline the possible source of the PTEs and their relation with soil texture, soil profile and human activities. Consequently, 14 sub-samples were collected from a sediment core of 30cm depth. The PTEs ranged as follows: Zn>Cd>Cr>Pb with mean concentrations of 194.5, 26.92, 13.42 and 8.07mgkg(-1), respectively. Pearson's correlation matrix showed positive correlations between Zn, Cd, P2O5, CaO, SiO2 and total organic carbon except for Pb and Cr, which seem to be interrelated, although they correlated negatively with all parameters. The principal component analysis (PCA) extracted three principal components representing 87.25% of the total variance. Similarly, hierarchical cluster analysis (HCA) confirmed the results obtained by the PCA, classifying the analyzed parameters into three different groups. The obtained data imply that PTEs concentrations in the study area are influenced by various factors such as anthropogenic and lithogenic sources. Zn, Cd, P2O5, CaO, SiO2 and organic matter (OM) probably have the same anthropogenic origin related to the phosphate industry, while Cr and Pb share the same natural source. The sediment contamination assessment proved that the samples of the study area are heavily polluted with Cd, moderately to heavily polluted with Zn and not polluted with Cr and Pb