Water Resources Research Act Program

Details for Project ID 2015OH441B

Soil development on coal mine tailings; impact on trace metal sources and mobility to acid mine drainage

Institute: Ohio
Year Established: 2015 Start Date: 2015-03-01 End Date: 2016-02-28
Total Federal Funds: $20,072 Total Non-Federal Funds: $20,072

Principal Investigators: David Singer

Abstract: Acid mine drainage (AMD) discharge has severe, long lasting impacts on water quality and stream ecology in affected watersheds. The remediation of environmental damage caused by these mines is also extremely costly. Between 2005 and 2012, monitoring and reclamation of over 300 km of streams and rivers in Ohio was done at a cost of over $25 million dollars. One such affected watershed in northeast Ohio is Huff Run, the focus of fieldwork in the proposed study. Since 1996, 18 AMD remediation projects have been built in the watershed at a cost of over $4.5 million. Restoration at sites such as Huff Run target discharge from surface and below ground mines, but typically do not target leaching from historic mine tailings. Surface mine spoil, a mixture of compacted, partly weathered fine-earth material and fragments of shale and other rock fragments account for nearly a third of the surface material in the Huff Run Watershed. The proposed research is focused on the geochemical processes occurring during mine tailings weathering to answer the following question: How does soil development on coal mine tailings potentially promote or limit the mobility of trace metals that may degrade water quality? Little is known about soil development on coal mine tailings, or how this impacts the rate of release of toxic elements. Despite the significance of long-term soil development on mine tailings, these processes are not specifically addressed and monitored during development and construction of AMD reclamation projects. Without an understanding of how critical geochemical processes which occur during soil development limit or promote metal and acid mobility, restoration will continue to be ineffective at providing an ecological benefit to the state. The objectives of this project are to: (1) Determine mineralogical abundance and trace metal concentration in soils developing on coal mine tailings vertically through a soil profile, and (2) Assess the effects of varying soil moisture on trace metal transport over time through a spring to fall field season. We hypothesize that during wetter periods, soluble Fe(III)-bearing phases will dissolve, releasing trace metals into pore solutions that can be transported into down-gradient AMD. The proposed work will focus on the Huff Run watershed because of the magnitude of AMD challenges and efforts towards improvement in the region. To achieve these objectives and test the central hypothesis, measurements of spatial and temporal changes in mineralogy and trace metal mobility will be performed. These measurements will allow for an integrated understanding of the geochemical processes driving these changes, and investigate their role in impacting water quality at the meter- to micron-scale. Solid phase characterization of soil core samples will include scanning electron microscopy, surface area and porosity measurements, trace element speciation and distribution, and total organic carbon concentrations. Further, a series of lysimeters will be installed near where the soil cores are sampled at both field sites to collect pore solutions for trace metal analysis over a 7-month period to measure the effects of soil moisture on trace metal transport over time.