期刊名称：Science et changements planétaires / Sécheresse
印刷版ISSN：1147-7806
电子版ISSN：1777-5922
出版年度：2005
卷号：16
期号：3
页码：183-187
出版社：John Libbey Eurotext
摘要：Figures See all figures Authors Saïda Niazi , Maria Snoussi , Ali Foutlane Faculté des sciences, Université Mohamed V, Département des sciences de la terre, BP 1014, Rabat, Maroc, Office national de l’eau potable (Onep), Laboratoire du contrôle de la qualité des eaux, Département de pollution et d’assainissement, Route d’Akkrache, Rabat, Maroc Key words: à venir Page(s) : 183-7 Published in: 2005 In September, 1989, the sudden appearance of high levels of manganese (5.6 mg/l) in the waters of the Abdeklkrim El Khattabi dam in Morocco — intended for the production of drinking water — resulted in shutting down the water treatment plant, with serious consequences for water management. This paper aims to identify the causes of this contamination and improve our understanding of it. A study of the entire watershed showed that the manganese comes from the Mn-mineralization lining many of the shale facies that cover much of the catchment area. Their easy erodibility, combined with the rare and irregular precipitation and the scarcity of vegetation, gives the Nekkor basin one of the highest erosion rates (5000 t/km/y) in Morocco and explains the high sediment load transported by the Nekkor river and the enormous silt buildup of the reservoir. There is therefore a high flow rate, estimated at approximately 680 t/y, of manganese, which binds preferentially to suspended matter. Our survey of the seasonal variations of Mn in the lake water clearly illustrates the concept of a chemical time bomb (CTB), that is, the remobilization of chemical elements stored in sediments in response to climatic change: a stock of Mn is stored temporarily in lake sediments during the wet season and a part of it is released during the dry period to cause natural manganese pollution.
