Evaluation de la contamination par Cadmium, le Chrome, le Plomb et le Manganèse dans les sédiments, les macro invertébrés et une plante aquatique (Roripa nasturtium aquaticum) dans l'Oued Rhumel et son affluent l'Oued Boumerzoug en zone urbaine

Abstract

Rhumel Wadi and its affluent Boumerzoug Wadi, one of the most important water ressources in Constantine, are subject to urbain and industrial effluents. In order to assess the level of trace metals contamination and the biological quality of thoes aquatic ecosystems, water, fresh sediments, benthic invertebrates and an aquatic plant (Roripa nasturtium aquaticum) were collected at stations along the Rhumel and Boumerzoug Wadi selected in an urban areas. Concentration of cadmium, lead, chromium and manganese in the different compartiments were determined by Atomic Absorption Spectroscopy. In addition, Biotic Index, and chemical parameters of water and sediments were determined. Results show, that heavy metals concentrations in water are not detectable, while an enrichment of sediment appear, espacially for cadmium and lead. The determination of thoese elements concentrations in Benthic invertebrates, indicate a probabel transfer from sediments towards this aquatic fauna espicially for chromium and lead. As for Roripa nasturtium aquaticum, the concentration of cadmium, lead, chromium and manganese in roots are greater than in stems and leaves, indicating significant metal immobilisation by roots. Manganese concentrations indicate a bioconcentration phenomenon for this plant, bioconcentration factors are superior to 1. The decline of taxa richness is observed at downstream stations, which are affected by wastewater and industrial effluents. The Biotic Index decreases dramatically from 8 at upstream stations to 2 at downstream station.