Resumen del producto

Mining for gold and silver in the El Triunfo mining area, Baja California, Mexico, has produced > 800,000 tonnes of mine-waste material. The mine has only been active intermittently since 1748 therefore tailings are scattered in the coastal system. Elemental migration is mainly caused by winds and tropical hurricanes, thus transported to the beach were metal deposits are formed. Sediments are discharged into the Pacific Ocean during intense storms when a sand barrier breaks. To evaluate the geochemistry of the alteration zone and the migration of the elements along the arroyo, 26 samples of surficial sediment were collected from close to the gold mine and along the path to the discharge in an evaporitic basin connected to the Pacific Ocean. Arsenic, Pb and Zn were analyzed with INAA, ICP-OES and ICP-MS and methods validated using certified reference materials. Elements enriched in the system shows maximum contents in tailings and ashes of As (50.5%), Pb (9.27 %) and Zn (4.96%) Sand sediments from the arroyo have maximum contents of arsenic (412 mg kg-1), Pb (1230 mg kg-1) and Zn (1950 mg kg-1). Comparison with background levels and Upper Continental Crust averages indicate severe contamination of these elements in this coastal system.

Palabras clave: sediments; Arsenic; gold ore mine; lead; zinc; arroyo

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