Evaluation of heavy metal contamination levels in river sediments and their risk to human health in urban areas: A case study in the Matanza-Riachuelo Basin, Argentina.

Anthropogenic contamination of Cd, Cr, Cu, Ni, Pb and Zn in riverbed sediments of the Pampean area (Matanza-Riachuelo Basin, MRB), Argentina, was evaluated using various indices: Geo-accumulation Index (Igeo), Contamination Factor (Cf), Metal Pollution Index (MPI), Pollution Load Index (PLI) and Contamination Degree (Cdeg). A database based on previous samplings of heavy metal concentrations at different sites in the Upper, Middle and Lower MRB was used. The Igeo and Cf values are calculated using selected local background (Pristine Pampean loess, LZB), and global average shale values (ASTW). Paired Igeo and Cf results with LZB and ASTW fall in dissimilar classes, especially in respect of Cd. In turn, MPI, PLI and Cdeg show similar results, as they do not have the same degree of confidence as Igeo and Cf. The Upper Basin, mainly rural, shows the following profile of sediment contamination: Cd > Ni > Cu ≫ Pb > Zn > Cr. The Middle Basin, which is at the periphery of a very industrialised and urban area, displays the following contamination profile for both Igeo and Cf: Cu > Pb > Zn > Ni > Cd > Cr. Conversely, in the Lower Basin, where land-use is urban/industrial, the levels of metal contamination are higher and appear in this order: Cr > Pb > Cu > Zn > Ni > Cd. Cadmium, Cu, Ni and Zn have shown no significant oral and/or dermal HQ nor carcinogenic risk but the potential risk posed by Cr and Pb must be taken into account. Maximum and mean values of Cr total carcinogenic risk (TCR) as well as Ni TCR also point to a health risk to children in the Lower Basin Area. All the data analysed confirm that industrial and urban growth without land-use planning, and a poor environmental legislation until the beginning of the 21st century, have not provided the necessary framework for sustainable development in the MRB.