[Impact of acid mining drainage on the quality of superficial waters and sediments in the Marrakesh region, Morocco].
The aim of the present study is the evaluation of the effects of the acid drainage of three abandoned mining sites: SB-Othmane, Kettara and Draâ-sfar, on water and sediment quality of the Tensift River and its two temporary tributaries, the Kettara and El-Coudia Oueds. These mining sites located near Marrakesh contain mining residues abandoned for ten to twenty years. They are presently in an agricultural region of the Haouz district. In each site, these uncontrolled mining residues present a high level of metallic sulphide and generate, during rainy periods, leaching products which have physical and chemical characteristics of acid mine drainage (AMD). These percolates display an acidic pH ranging from 2.5 to 5.2, a high electric conductivity, large amounts of sulphate and heavy metals, especially under dissolved form (e.g. Cd: 17.34 mg l(-1); Fe: 1734 mg l(-1); Zn: 3935 mg l(-1)). Except for Pb, the free ionic form is the most abundant metallic form, as showed by calculations using the speciation GEOCHEM program. The analysis of water and sediments of the surrounding superficial aquatic ecosystems shows a modification of water chemical facies and an enrichment in heavy metals, mainly under the solid phase for Fe, Pb, Cu, Co, Cr and Ni, and under dissolved fraction for Cd and Zn. The dissolved fraction of these metals is dominated by the free ionic form, considered as available for organisms. Furthermore, sediments contain important quantities of heavy metals (Pb: 1450 microg g(-1), Zn: 1562 microg g(-1)) with an available fraction which is higher than 40% for the Cd and Zn. The abundance of trace elements (free ionic and available forms) in water and sediment presents a durable risk of their transfer to food chains.
El Gharmali
A
A
Univ. Cadi Ayyad, FSS, Dépt. Biol., Lab. Analyses. BP/2390, Marrakech 40 000, Maroc.
Rada
A
A
El Adnani
M
M
Tahlil
N
N
El Meray
M
M
Nejmeddine
A
A
D000143:Acids; D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000032:analysis; D007220:Industrial Waste; D019216:Metals, Heavy / Q000032:analysis; D008906:Mining; D009018:Morocco; D045483:Rivers / Q000737:chemistry; D013431:Sulfates / Q000032:analysis; D014874:Water Pollutants, Chemical / Q000032:analysis*
D000143:Acids; D007220:Industrial Waste; D019216:Metals, Heavy; D013431:Sulfates; D014874:Water Pollutants, Chemical