Trace elements migrating from tailings to rock varnish laminated sediments in an old mining region from Nelson, Nevada, USA

Abstract

The dispersion and influence of soluble and particulate trace elements (TEs) present in the materials from abandoned mines is an imminent problem on terrestrial and aquatic environments. The goal of this research is to provide a broader view of such transport, assessing particle size distribution and TE interactions (e.g., scavenging) with mine tailings and locally derived sediments transported by water in arid region. Sand grains from wash sediment were collected from a dry ephemeral wash in Nelson, Nevada where the Techatticup Mine and Mill worked between 1850 and 1960. Samples were evaluated to determine the association and behavior of certain metals and metalloids including aluminum, arsenic, barium, cadmium, copper, chromium, iron, manganese, lead, selenium, vanadium, and zinc to rock varnish laminated sediments. Results show that some metals and metalloids were more concentrated on larger particles whereas others indicated the opposite tendency. For example, As was greatest on silt fractions and least on coarse fractions, while Se was detected only on silts. Cr, Cu, Fe, Mn, Pb, and Zn concentrations all increased with decreasing particle size (silt > sand > coarse), whereas Al, Ba, and V showed the opposite trend (silt < sand < coarse). The enrichment factor (EF) of Cu, Zn, Pb, As, and Se were lower in mine tailing sediment treated with wash than those obtained for source material. However in treated wash sediment samples, the high EFs of Ba, Cr, V, and Mn suggested a possible greater affinity of these metals to the Al, Fe, and Mn oxides from the RV sediment. The data found in this study show that transport of contaminated sediments in arid regions could lead to the enrichment of some TEs in down-gradient areas from source materials.