Niveau de contamination par les ETM des sédiments du barrage Béni Haroun et des oueds qui l’alimentent

Abstract

The main goal of this PhD was to evaluate the impact of the anthropogenic activities (urban, industrial or agricultural activities) on aquatic ecosystemsin the northeastern region of Algeria. The evaluation focused on the Rhumel and Endja wadis, which drain urban, industrial and diffuse discharges and feed the Beni Haroun dam, the largest source of drinking water, irrigation and fishing in Algeria. In order to achieve our goal, this work was based on a multiple approach involving the terrain, with 6 campaigns of water and sediment sampling on 16 points spread over the wadis and reservoir lake, an analytical approach through physicochemical characterization of water and sediments, a biological and ecological approach by calculating biotic index via benthic macroinvertebrate fauna, and assessing the bioavailability of trace metals through metallic contamination of macroinvertebrates and four species of fish Cyrinus carpio, Abramis brama, Carassius carassius et Barbus callensis. The sediments of the Béni Haroun dam and wadis are slightly alkaline, have high conductivity and medium organic matter content.The spatio-temporal data of the pseudo-total levels of ETM in the sediments record the following order of abundance: Fe > Zn > Pb > Cu > Se. The concentrations are : 5920-33400 μg/g for Fe, 28,50-311,35μg/g for Zn, 2,30-115,35 μg/g for Pb, 2,25-41,25μg/g for Cu and ,02-2,69μg/g for Se. Indeed, the spatial distribution of heavy metals content reveals natural levels for Cu and Zn. Contamination by Fe, Se and Pb is widespread and affects all stations. This result has also been confirmed by the geoaccumulation index (Igeo) and the contamination factor (CF), which suggest that these high levels are essentially anthropogenic. The collected macroinvertebrates reveal polymetallic contaminations dominated by iron, zinc and lead. Similarly, the levels of the fish's TMs reflect contamination of the ichthyological fauna of the Beni Haroun dam. The levels determined in the muscles of the four fish species exceed the critical contamination values regardless of the metals studied, making them unfit for consumption as they pose a risk to human health.