Trace element biogeochemistry of a wetland system receiving mine drainage.

摘要

Trace element removal and retention in a natural wetland/pond system was investigated at an abandoned silver/lead mine located in American Fork Canyon, Utah. The mine portal water was neutral in pH, contained Fe oxides, and high concentrations of Zn, Cd, Pb, and As. The beaver pond served as an adequate sedimentation basin for the removal of trace elements from the mine drainage at low flow when sufficient retention time was provided for precipitation and sedimentation processes to occur. The stability of the pond sediments to retain the trace elements was investigated under two laboratory induced-redox environments, oxygen-limiting and ambient conditions. Maximum trace element retention occurred within the sediment samples exposed to oxygen-limited conditions, primarily controlled by Fe2+ oxides and Fe2+ carbonates. When these reduced sediments were exposed to atmospheric oxygen, trace element retention immediately decreased due to the oxidative dissolution of these reduced Fe solid phases.