Paper No. 298-8
Presentation Time: 10:45 AM
THE EFFECTS OF BIOGEOCHEMICAL SINKS ON THE MOBILITY OF TRACE METALS IN AN AREA AFFECTED BY ACID MINE DRAINAGE, HUFF RUN, OHIO
Currently, a watershed restoration group has made progress in remediating surface water contributions to the Huff Run Stream in Mineral City, OH, which is heavily affected by acid mine drainage (AMD) due to historical coal mining. However, the accumulation of AMD sediments on the streambed has prevented the overall ecological health of the area from rebounding. A proposed remediation plan includes dredging, however the efficacy of doing so while preventing further iron buildup and the potential release of trace metals during such an operation is uncertain. The objectives of this research are to examine the effects geochemical sinks can have on the fate and transport of trace metals in order to understand the possible side effects of dredging on the Huff Run. This work aims to build a framework on which to base proposed remediation plans at a wide range of acid-mine drainage impacted sites. To achieve these objectives cores were gathered from the Huff Run and the Farr tributary, where a large amount of AMD is discharged into the Huff Run. These core sediments were analyzed through XRD analysis to understand the abundance and distribution of mineral phases, and ICP analysis to provide information on the amount of trace metals and understand what mineral phases they are associated with. Groundwater piezometers installed in AMD-bearing sediments and streambed sediment were used to quantify changes in trace metals concentrations. The analyses of cores gathered from the stream provide evidence that overtime deposited iron oxides go through thermodynamic transformations into more stable phases, mainly goethite. On-going work aims to determine how mineralogical transformations impact the availability of trace metals. Hydraulic head values gathered the piezometers have shown that hyporheic exchange is occurring, despite the deposition of fine grained sediment and iron oxides from historical mining. Water samples collected from the piezometers have been analyzed for pH and conductivity and show consistent changes as the water is exchanged from the surface and groundwater. On-going work aims to determine how this exchange affects the transport of trace metals.