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.

Butte, Montana is the site of a world class copper deposit that has been mined nearly continuously since the 1870's. Tailings deposits, a legacy of early mining practices, are abundant in the floodplain of the Clark Fork River, which has its headwaters near Butte. Tailings released by large-scale flooding in the early 1900's form a patchwork in the floodplain. Waters that contact the pyriterich tailings are generally acidic and contain elevated copper, zinc, and arsenic levels.Thinner tailings deposits (e.g. less than 15 cm) are fully oxidized and have become naturally re-vegetated. In areas with thicker tailings deposits, low pH (3 to 4.5) persists and tailings are devoid of vegetation. Evaporation from bare tailings concentrates metal sulfate salts at or near the surface. The bare tailings are susceptible to erosion and water flowing across the tailings dissolves metals and contributes metal loads to the Clark Fork River. In the middle and late 1980's, large fish kills occurred in the Clark Fork after thunderstorms rinsed soluble metals, especially copper, into the river.In 1990 and 1991, 4 km of the Clark Fork River near Warm Springs, Montana, was reclaimed using liming and both deep and conventional tillage techniques to reduce the mobility of metals in the floodplain and to allow reestablishment of vegetation. Successful stabilization of the floodplain soils has been amply demonstrated and phytostabilization was proposed as a cornerstone of the remediation efforts for the Clark Fork River superfund site. Environmental monitoring of the Clark Fork Demonstration project over a 14 year period is described in this paper.

Concentrations of Pb in whole blood from 222 cattle (Bos tarus L.) representing nine herds were determined. Lead blood levels were significantly (P ≤ 0.05) elevated for herds near a primary lead smelter compared to a background herd. Herd Pb blood levels were significantly correlated to distance from the smelter (r = −0.86), and to soil Pb concentrations (r = 0.96). They were also moderately correlated (r = 0.61) to vegetation Pb levels. Soil may be more important than forage as a source of Pb for these cattle. Immature cattle, less than 1 yr old, had higher (P ≤ 0.05) Pb blood levels than mature cattle. A total of 15 animals (all immature) exhibited Pb blood values above 35 µg dL−1. Twenty‐one animals had elevated (22–35 µg dL−1) Pb blood levels. Most cattle (80%) tested near the smelter and all cattle from the background herd had Pb blood levels in the normal diagnostic range (1–21 µg dL−1).

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