Exploring the Toxic Legacy of Urbanisation: Investigating Heavy Metal Contamination in Saida's Urban Sediments

This study investigated urban pollution in the watershed of the city of Saïda, located in northwestern Algeria, focusing on heavy metals and organic pollution in sediments from urban drainage. The results identified, characterised and quantified these pollutants by comparing the total trace metal content of sediment samples with standards and reference values. They also highlighted the cycle of pollution generation and regeneration in the urban catchment, influenced by rainfall events and sediment extraction periods, and demonstrated the role of the drainage network as a physico-chemical reactor in the mobilisation of pollutants. The extent of pollution is assessed using pollution indices and factors, which showed high concentrations of various metals in the sediments, indicating significant pollution. Contamination levels ranged from very high for cadmium to moderate to high for lead, copper and chromium, while zinc and nickel showed low contamination. Conversely, cobalt and iron showed no contamination, but the sediments remained highly contaminated according to the contamination criteria. The results showed an anthropogenic enrichment exceeding critical thresholds and an ecological risk ranging from high to severe.