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UNDERSTANDING THE IMPACT OF ENVIRONMENTAL VARIABLES ON THE LEACHING OF MERCURY-CONTAMINATED MINE WASTES FROM THE SULFUR BANK MERCURY MINE, CLEAR LAKE, CA
Citation:
Randall*, P M. UNDERSTANDING THE IMPACT OF ENVIRONMENTAL VARIABLES ON THE LEACHING OF MERCURY-CONTAMINATED MINE WASTES FROM THE SULFUR BANK MERCURY MINE, CLEAR LAKE, CA. Presented at EPA Workshop on Mining Impacted Native American Lands 2003, Reno, NV, 9/9-11/2003.
Description:
For nearly a century, Clear Lake in northern California has received inputs of mercury (Hg) mining wastes trom the Sulfur Bank Mercury Mine (SBMM). About 1.2 million tons of Hg-contaminated overburden and mine tailings were distributed over a 50-ha surface area due to mining operations trom 1865 to 1957. In 1957, the mine was shut down. In recent yrs, this site has been a Superfund site and has experience some minor corrective actions. However, Clear Lake remains under a fish advisory due to methyl mercury and continue to cause health concerns among the tribal communities( i.e. Elem Tribe) along the lake.
This study was undertaken as a part of developing treatment alternatives for waste materials, primarily waste rock and roaster tailings, trom sites contaminated with mercury (Hg) mining wastes. Leaching profiles of waste rock over a range of different pH and oxidation-reduction (Eh) conditions were performed. Since iron (Fe) is present in large quantities in mining wastes, the effect of Fe on leaching ofHg was also determined. Results show that the Hg concentration increased as the pH ofthe suspension increased until a pH value of 10.65. Thereafter, the Hg concentration decreased sharply. The Hg concentration in presence of Fe decreased significantly (l/10th to l/1O0th). Kinetics results show a relatively slow rate ofleaching in presence offerric ions. The results obtained trom the present study are being used to predict the fate and stability of Hg present in the environment, and will therefore, be useful in dictating the nature and suitability of any remediation treatment.