Mobility of Heavy Metals in Soils and Tailings at the Hanover and Bullfrog Tailings Sites, Silver City, New Mexico PDF Download

Author: Tanya G. Baker
Publisher:
ISBN:
Category : Soils
Languages : en
Pages : 142

Get Book Here

Book Description
The Hanover Mining District, located east of Silver City in south west New Mexico, has been mined since at least the 1600's. The majority of production was for iron and base metals such as Cu, Zn, and Pb. The two sites of interest in this study are the Hanover and Bullfrog tailings piles. Tailings were produced from Zn-Pb sulfide-vein deposits. The main ore mineral at Hanover is sphalerite. Ankerite, specular hematite, pyrite, and pyrrhotite are common gangue minerals. The main ore minerals at Bullfrog (derived from three mines) are sphalerite and galena. Gangue minerals include quartz, pyrite, manganiferous calcite, chlorite, and rarely barite. Movement of heavy metals from the tailings piles may occur by wind transport of metal-containing particles, fluvial transport, aqueous transport, and/or plant uptake. To determine the mobility of heavy metals present at the sites, surrounding soils, vegetation, and surface water were sampled and analyzed. Soils were sampled at the surface and at depth to determine possible downward movement. Foliar samples were taken to determine metal concentrations in plants on and near the tailings. Surface water samples were taken from Hanover Creek above, adjacent to, and below the Hanover tailings to determine possible contamination from the tailings. Surface soil samples taken in an area affected by wind-transported tailings material show slightly elevated Pb, Zn, and Cu concentrations above background. Concentrations of these metals drop to background levels below 2-4 cm in depth. Plant samples show little uptake of heavy metals even in samples taken on the edge of the tailings piles where wind transported material had engulfed the plant. Water samples taken adjacent to and below the Hanover tailings contain fewer total dissolved solids and lesser concentrations of the main ions SO4, and Ca than those taken upstream of the tailings. This is probably due to the presence of calcium carbonate in the tailings material. These results, together with the alkaline nature of the soils and arid climate of the southwest United States, indicate the probability of dissolved aqueous transport of heavy metals away from the tailings is low. It is recommended that the tailings be covered with topsoil and revegetated to decrease any effects the tailings may have on the surrounding environment.