assessing heavy metal contamination in surface water and sediments of the tafna river (north-west of algeria)

Water and sediments have become a major threat. heavy metals, some of which are potentially toxic, are distributed in different areas by different routes. tafna river was studied upstream and downstream under contrasting hydrological conditions during the year 2020.the different levels and sources of pollution are assessed by combining geochemical indicators: geoaccumulation index (gi-go), contamination factor (cf), pollutant loading index (pli) and supplemented by correlation matrix (cm) as statiscal analyses added principal component analysis (pca). the elements analysed were physical and chemical parameters (ph, do, electrical conductivity ce and, cod bod5), and the metallic elements (fe, cd, pb, cu, mn and zn). they were classified based on how contaminated they were: for the water compartment (fe> mn>cu>pb>cd>zn), while for sediments (zn> pb>fe>cd>cu >mn). the results suggest that the chemical composition of the waters of the tafna river is influenced by the lithology, which contributes to the enrichment of the sediments. all of the indicators suggest an average levels of sediment and water pollution at the tafna's summit, then decreases towards the bottom due to the geomorphology with multiple sources of pollution. as a result, our study offers the first comprehensive information on the amount of heavy metals present in the riverbed's sediment and water.