Procesos erosivos en jales de la presa i de nacozari de garcía, sonora y su efecto en la dispersión de contaminantes

The operation and exploitation of the Pilares breccia-pipe copper ore deposit and its subsequent cessation of activities in 1945 generated approximately 20 million tons in mine tailings and waste, currently covering a 19 hectares surface located within the urbanized area of Nacozari de Garcia, Sonora. The studied mine tailings are unconfined, with unstable slopes of 50°, lack of vegetation and seasonal efflorescent salts haved formed onthe surface. Such characteristics generate high eolian and water erosion and the possiblecollapse of material. In this work, calculated erosion is classified as severe to very severe. Granulometric characteristics of the tailings mark significant differences in theintensity of water erosion. The physical characterization of the tailings shows two areas of different granulometry that influence in the oxidation of sulfides and metal release: an area of large particle size, and another of fine particle size produced by the flotation process. Climate indexes were estimated for a time period from 1960 to 2011. The aridity index of Martonne shows a rank from 47 to 66, varying from humid in thé60s and́70s to perhumid in thé80s, and humid at present. The Lang index shows values from 15.2 to 22.8, which classifies as a steppe. Copper contents in residential soils and airborne dust collected at two meters height exceed the geochemical background.