Ecological and health risk assessment, geochemical background prediction and source identification of potentially toxic elements in sediments: a watershed-scale study (data update).

A study was conducted on thirteen wadis in the Kebir Rhumel watershed, located in northeastern Algeria, to assess potentially toxic elements (PTEs) concentration in surface sediments. Samples were collected from 37 sites during both wet and dry seasons to provide a general classification of pollution levels and to assess the ecological and health risk of these elements. Multivariate data analysis was used to detect areas with distinct polluting characteristics and trace their natural and/or anthropogenic sources. The levels of PTEs (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) were determined using flame atomic absorption spectroscopy. The dominance of various PTEs in the sediments followed the sequence: Fe > Mn > Zn > Pb > Cu≈Cr > Ni > Co > Cd, for both seasons. The concentrations measured showed some levels exceeding the required standards, especially for Cd, Cu, Fe, Mn, Pb and Zn, while Co, Cr and Ni remained below the critical levels. The following mean concentrations were recorded: 1.4/1.2 (Cd), 45.6/48.2 (Cr), 12.5/11.2 (Co), 45.6/48.8 (Cu), 36796/35480 (Fe), 25.4/23.6 (Ni), 248/268 (Mn), 72.9/71.2 (Pb) and 156/131 µg/g (Zn) for wet/ and dry seasons, respectively. Principal components analysis revealed that Cd, Pb, Cu and Zn pollution in the Kebir Rhumel watershed was predominantly anthropogenic in origin, whereas the PTEs (Cr, Co, Fe, Mn and Ni) were primarily of pedological/geological origin. The carcinogenic and non-carcinogenic risks associated with chromium concentrations in sediments are evident for children in both high and low water events, with ingestion as the main route of exposure. The results emphasize the urgent need for focused attention on the studied area due to the high likelihood of adverse health outcomes.