Trace Elements Mobilization in Sediments of the Eagle Wash, Nelson, Nevada (USA)

Abstract

This study examines the mobilization of cyanide (CN-) and trace elements from the Eagle Milling Site situated in the Eagle Wash of Nelson, Nevada. Contaminants (CN- and mercury [Hg]) utilized for the extraction of precious metals from ores are subject to environmental release, but concentrations of other trace elements in sediments and their enrichment ratios indicate that mobilization of trace elements lead (Pb), arsenic (As), selenium (Se), and barium (Ba) has also occurred. Storage of milling wastes in Eagle Wash and subsequent storm water mobilization and transport has resulted in increases in CN-, Hg, Pb, As, Se, and Ba in wash sediments some 6,000 m from the source area. On the basis of enrichment ratios, the Eagle Wash was found to contain CN-, Hg, Pb, As, and Ba above background levels in wash sediments. Selenium increased slightly in concentration; chromium (Cr) decreased consistently; and silver (Ag) and cadmium (Cd) were not detected. Cyanide, Hg, Pb, Ba, Se, and As enrichment ratios were > 1.5, indicating anthropogenic enrichment in sediments, whereas Cr enrichment ratios were <1.5, indicating no anthropogenic enrichment.