Abdelkrim Charef

Heavy elements in the phosphorite from Kalaat Khasba mine (North-western Tunisia): Potential implications on the environment and human health

Tunisia is one of the largest phosphate producers in the world (more than 10 million tons per year since the early nineties). The Kalaat Khasba mine (NW of Tunisia) has operated from 1893 until 1993 and data demonstrate that, in the phosphorites of Kalaat Khasba, Cd is enriched 105-208 times, when compared with shales, and U is enriched by a factor varying between 18 and 44. The general trend shows an increase in heavy elements content with decreasing particle size. On the other hand, concentrations of Sr, Cr and U exhibit the same distribution for the different size fractions. It was found that Cd concentrations exceed the allowed EC soil limits for growing crops. Hence, owing to the tailings exposure and to the mobilisation of the finest particles by rainfall and wind, Cd could have detrimental effects on human health and on the environment because a significant portion of Cd was found in the exchangeable form.

Vecteur de la pollution metallique du bassin versant de l’Oued El Bey vers le Golfe de Tunis (Tunisie)

Résumé L’Oued El Bey, qui draine 60% de la charge polluante hydrique de plusieurs agglomérations urbaines du Nord-Est de la Tunisie, est un exemple représentatif du transfert des métaux lourds résultant de l’activité industrielle et urbaine. Il fournit une indication sur le devenir et la répartition des métaux lourds dans le Golfe de Tunis. Dans la fraction dissoute, Cd, Pb, Co et Hg ne sont pas détectés mais Zn varie entre 0,01 et 0,07 μg/L. Les concentrations du Mn, Zn, As, Ni, Pb, Cu et du Cd sont très élevées dans la fraction particulaire par rapport à la fraction dissoute, avec un coefficient de partage Kd de l’ordre de 106, ainsi que dans les sédiments du lit de l’oued pour Pb et Zn. La pollution par les métaux la plus élevé de l’Oued El Bey a été trouvée pour Zn, Pb et Cu: les concentrations variaient respectivement entre 1698,9 et 14575, de 0 à 2153,7 et de 0 à 3431,8 μg/g. La variation spatiale des teneurs en métaux lourds confirme l’effet des eaux usées rejetées dans l’Oued El Bey. Les teneurs de ces métaux lourds dans les trois phases dissoute, particulaire (MES) et sédiments confirment que la MES constitue le vecteur de transport principal via la Sebkha Soliman vers le golfe. L’examen des rapports des différents éléments (Pb, Cu et Cd) par rapport au Zn dans les sédiments de l’oued montre une augmentation au niveau de la confluence de l’Oued El Bey et de son affluent l’Oued El Meleh, ce qui signifie que les apports sédimentaires de cet affluent contrôlent la signatutue chimique des sédiments de l’Oued El Bey. Editeur Z.W. Kundzewicz; Editeur associé B. Touaibia Citation Khadhar, S., Mlayah, A., Chekirben, A., Charef, A., Methammam, M., Nouha, S., et Khemais, Z., 2013. Bassin versant Oued El Bey: vecteur de transport de la pollution métallique vers le Golfe de Tunis (Tunisie). Hydrological Sciences Journal, 58 (8), 1803–1812.

Effect of long-term irrigation with treated wastewater of three soil types on their bulk densities, chemical properties and PAHs content in semi-arid climate

This study aims at understanding the effect of soil texture and water quality (treated wastewater and groundwater) on soil physical (bulk density) and chemical (pH, salinity, CEC, total organic carbon and carbonate content) properties and on organic pollutant concentrations (polycyclic aromatic hydrocarbons) in different soil types in semi-arid regions. Results showed that the long-term irrigation with treated wastewater increased the bulk density in lithosoil and saline soil, while it decreased it in the isohumic soil. Moreover, the application of a double volume of treated wastewater enhanced the soil bulk density. However, irrigation with groundwater did not reveal any significant effect on soil bulk density. Also, the long-term impact of groundwater on the physico-chemical properties varies from one soil type to another. Multivariate analysis (principal component analysis) showed that different soil parameters such as soil texture and bulk density were determinant in soil evolution. The treated wastewater is considered as potential source of pollutants, and its long-term application induced high concentration of organic pollutant. Actually, the irrigated soils are heavily contaminated, and the carcinogenic molecule concentrations were about 1.2–7.6 times higher in these perimeters than in control soils.

Effect of Water Quality on Heavy Metal Redistribution-Mobility in Agricultural Polluted Soils in Semi-Arid Region

Abstract Mornag Plain is a coastal area of the Mediterranean basin, which has undergone an agricultural industrial boom. The aim of this study was to investigate the different water qualities used for irrigation on heavy metal mobility in these polluted agricultural soils. The geo-accumulation indices for heavy metals (Ni, Cr, Pb, Cd, Cu, and Zn) revealed that industrial activities and used treated wastewater (TWW) contributed to soil pollution, and water irrigation always decreased this contamination. After long-term use of different water types, high perturbation of heavy metal redistribution has occurred. Groundwater use altered all heavy metal redistributions in the irrigated soil among various soil-solid and soil-solution fractions, as compared to the unirrigated soil. Slight acid water use transferred some metals from different solid phase components into water-soluble and exchangeable fractions. However, TWW use transformed some Ni, Cr, Cd, Cu, and Zn from water-soluble and exchangeable fractions to less labile fractions, particularly into organically bound fractions. Reuse of conventional water within the same soil decreased the whole soil redistribution index values, indicating tendency to return to the pattern of distribution of groundwater-irrigated soil.

Candidate areas for wastewater stabilization ponds utilizing GIS and metal adsorption capacities of native clayey deposits: Mornag case study (NE Tunisia)

The main objective was to determine candidate areas for proposed wastewater stabilization ponds (WSPs) to treat municipal wastewater from rural communities in Mornag, Tunisia. To attain our goal, geology, topography, proximity to surface water, proximity to residential areas and proximity to main roads were gathered and analyzed in a geographic information system. For each criterion, a suitability map was created by classifying the study region into two discrete categories: suitable and unsuitable areas. A final suitability map showing candidate areas for WSPs was produced by overlaying different resulting criteria maps. Then, batch adsorption experiments and infiltration–percolation tests by experimental column were carried out to determine the efficiency removal of native clayey deposits of candidate areas for Pb, Cd and Cu in the presence or absence of organic matter, in order to verify their potential use as filter substrate of heavy metals from treated wastewater by WSPs. The performances of filter materials used in wastewater treatment systems were determined. Thus, their lifetime could be estimated.