Resumen del producto

Gold and silver mining in the El Triunfo (ET-MZ) area on the southernmost Baja California Peninsula Mexico has an average grade of Ag calculated to 131- 436 g Mg-1. Tailings are scattered in the coastal system due to the intermittent mining activity occurring since 1748. Elemental migration is caused by winds and tropical hurricanes which may occur in summer. Silver, Cu and Ni concentrations were measured in tailings in the ET-MZ and in superficial sediments along the Hondo – Las Gallinas – El Carrizal arroyo in order to determine the enrichment and spatial distribution along the dry river (arroyo) to the discharge into the Pacific Ocean. Chemical analysis was realized using an ICP-MS and methods were validated using certified reference materials. Results show maximum contents of 207, 1660 and 14.5 mg kg-1 of Ag, Cu and Ni, respectively in tailings and of 36.1, 78.8 and 111 mg kg-1, respectively in sediments. Normalized enrichment factors (NEFs) were calculated for sediments along the arroyo using Earth´s crust averages. NEFs calculated for silver show very severe to moderate contamination. For Cu and Ni, however, NEFs were low close the mining zone and impoverished in almost all the samples (<3).

Palabras clave: heavy metals; geochemistry; sediments; silver; mine wastes

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