Fate of contaminants at an abandoned mining site in an arid environment
Mining exploitation of mineral resources in the American West has been an important factor in westward expansion. However, this legacy might pose a significant risk to the wider environment. Previous assumptions were that abandoned mining sites in hyperarid regions posed no significant threat. Three washes in Nelson, Nevada (USA) were evaluated to determine if trace elements and Cyanide from abandoned mining sites have migrated downwash in a hyperarid climate. Data show that this assumption is true with respect to current environmental conditions, however, future climate changes have not been considered. Data show that the Carnation, Eagle, and Techatticup wash sediments contained low concentrations of CN[sup]-, Hg, Ag, As, Pb, and Se, but above background levels. It was found that contaminated sediments containing CN[sup]-, Ag, As, Ba, Cd, Cr, Hg, Pb, and Se have migrated at least 6000 m. Furthermore, research has shown that creosote bush in the affected parts of the washes has accumulated small amounts of trace elements As, Cr, and Se in its leaves, but other trace elements present in wash sediments (Ag, Cd, and Pb) have not been taken up. The current environmental conditions provide for a low risk to downwash areas based on low concentration of CN[sup]- and trace elements when compared to the United States Environmental Protection Agency's screening levels. However, if environmental climate changes were to occur, the risk to downwash environments may increase. There are more than 1000 abandoned mining sites in Nevada and countless more across the globe that are located in similar environments. It has been shown that it is possible for mine tailings in Nelson, Nevada to migrate in a hyperarid climate indicating a site may pose a greater risk as a result of climate change. Sites with significantly more contaminated sediments could be at a greater risk for waste to be mobilized into the wider environment due to climate change. If the local environment is effected by an increase in precipitation or intensification of storm events, pathways for contaminants to enter the wider environment could ultimately impact or pose a more significant risk to the wider environment.