Arsenic Transport in Contaminated Mine Tailings following Liming

Abstract

The practice of liming to remediate contaminated soils and mine tailings has the potential to mobilize arsenic (As), due to the pH dependence of As sorption reactions on oxide minerals and layer silicates. The objectives of this study were to determine the effects of liming on As mobility in mine tailings and identify possible mechanisms controlling As mobilization with increased pH. Six mine tailing samples obtained from an abandoned copper smelter near Anaconda, Montana were analyzed for total As and soluble constituents using saturated paste extractions. Concentrations of soluble As among the six samples did not correlate with total As, but were more closely related to pH. Saturation indices with respect to known metal arsenate solid phases suggested that metal arsenate solid phases were not controlling soluble As in these samples. Two low pH samples (pond tailings and reprocessed tailings) were chosen for more detailed chemical characterization and unsaturated column transport experiments before and after liming. Soluble As concentrations measured in column effluent increased by factors of 10 (reprocessed tailings, RT) to 400 (pond tailings, PT) following liming. Sequential extractions of these tailing samples showed that the PT contained significantly higher “labile” As relative to the RT, consistent with amounts of As mobilized after liming. Further characterization of these samples using scanning electron microscopy (SEM) and energy dispersive analysis of x‐rays (EDAX) suggested that these samples do not contain discrete metal arsenate solid phases. Based on this suite of experimental data, increased mobility of As with liming appears to be consistent with the pH dependence of sorption reactions of As on Fe oxide minerals rather than dissolution‐precipitation reactions involving As.

Phytoremediation of contaminated soils and groundwater: lessons from the field

“…The practice of liming to remediate contaminated soils and mine tailings has the potential to mobilize arsenic due to the pH dependence of As sorption reactions on oxide minerals and layer silicates (Jones et al 1997). It may also be of concern for other trace elements such as Cu, Mo, U, V, and Se.…”

Mineralogical and geochemical characterization of arsenic in an abandoned mine tailings of Korea

“…Until now, mine tailings are frequently treated with lime amendment and/or are simply placed in landfills at designated disposal sites. Lime treatment, however, may result in enhanced As mobilization due to the pH dependence of As sorption by mineral solid phases (Jones et al 1997). When the conditions turn anaerobic, the reductive dissolution of As-bearing iron hydroxides occurs, causing desoprtion of arsenate and arsenite species (McGeehan & Naylor 1994).…”

Impact of unconfined sulphur-mine waste on a semi-arid environment (Almería, SE Spain)

“…Furthermore, in soil with CaCO 3 , Ca 2þ ions reduce adsorption and increase solubility of Cd 2þ (Lagerwerff and Brower, 1972). In the case of As, because it is co-precipitated fundamentally with Fe oxyhydroxides, and the quantity precipitated decreases as pH increases (Jones et al, 1997;Tyler and Olson, 2001;Simón et al, 2005), high solubility and low precipitation and/ or adsorption of As would be expected in Area B, characterized by a basic pH and a relatively low Fe concentration (similar concentration as in Area C). The low Fe concentration in Area B would be attributable to the low concentration on sulphur-mining wastes (mean ¼ 62 g kg À1 ), far lower than in other types of mining wastes, such as sulphide (mean ¼ 359 mg kg À1 ; Alastuey et al, 1999).…”