Abstract

In 2015 an extraordinary hydrometeorological event occurred in the southern Atacama Desert (northern Chile) that resulted in a catastrophic flood in the city of Copiapo. A large volume of detrital sediments was transported downstream, provoking an economic and environmental disaster in the Copiapo Valley, a region dominated by mining activity. Loads of sediment and residues were moved by the flow and deposited throughout the urban area of Copiapo. The current study explores the geochemical features and associated pollution risks of metal(loid)s in sediments collected in different points of the city after the flood event. Results revealed that, despite the high natural concentration of elements due to geogenic chemical composition of the area, geoaccumulation of Al, As, Cd, Co, Cu, Hg, Fe, Mn, Ni and Pb showed moderate contamination when compared to the background concentrations of the area. Furthermore, Hg, originating from legacy mining practices, constituted the main environmental risk associated with the flood sediments. Finally, data from this study were compared to other flood events and mining spills; some contaminants in the 2015 flood sediments in Copiapo were higher than some historical mining disasters. This work highlights the potential intersection between anthropogenic activities (mining) and extreme hydrometeorological events (floods) in arid environmental degraded areas.