Experiments were conducted on pilot study spent tuffaceous ore and native soils to predict arsenic teachability and subsequent attenuation from a proposed spent ore pile at an Idaho gold mine. The experiments were patterned after the graded serial batch extraction tests developed by Houle and Long and were designed to mimic the leachate movement through time and space conditions not attainable by column tests. Each extraction sequence involved consecutive contact with three batches of spent ore followed by three batches of soil. Four different samples of soil collected from the proposed mining site were tested in this manner. Solution aliquots were taken from each batch, filtered, and analyzed for arsenic and pH. Four extraction sequences were run for each soil type at increasing liquid-to-solid ratios to simulate increasing durations of leaching and attenuation. A total of 16 extraction sequences were conducted.
Analytical results of the solution aliquots showed an increase in arsenic concentrations on contact with successive batches of ore, but a decrease in concentration after contact with soil batches. For the conditions simulated, adsorption and precipitation by natural soils would prevent contamination of ground and surface waters. The results are consistent with the known aqueous geochemistry of arsenic.