Appalachian surface coal mining operations fracture rocks (termed mine spoils), resulting in the weathering of minerals and release of water-soluble ions to streams. Collectively, the concentration of water-soluble ions in streams is called total dissolved solids (TDS) and streams with elevated TDS often have altered biota. The surficial, subsurface, and discharge properties of mine spoils influence TDS discharge concentrations. This study aimed to improve understanding of how hydrologic and hydrochemical processes occur and function in coal mining areas. These processes were characterized by infiltration and dye staining tests, mine spoil leaching experiments and modeling, and mining-influenced stream discharge monitoring. Results indicate that many factors influence hydrologic and hydrochemical processes in Appalachian coal mining areas, but these processes evolve over time as subsurface flow paths develop, mine rocks weather, and TDS is released from mine spoils. Fourteen years after placement, mean infiltration rates of mine soils reclaimed with trees were statistically greater than areas reclaimed with grasses, and different subsurface flow types were evident, indicating vegetation type influenced hydrologic processes. Specific conductance (SC) leaching patterns from mine spoils conformed to an exponential decay and linear segmented regression model. Maximum SC values (1108 ± 161 µS cm⁻¹) occurred initially during leaching, exponentially decayed, then exhibited linear SC releases (276 ± 25 µS cm⁻¹) that were elevated relative to natural background levels at the end of leaching. Major element (S, Ca, Mg, K, Na) leaching patterns resembled those of SC, whereas trace elements (As, Cd, Cu, Ni, Pb, Se) transitioned to linear release earlier in the leaching period. Mining-influenced stream SC discharge patterns varied by season and by precipitation amounts during storm events. Storm responses were characterized by either infiltration-excess overland flow or delayed SC releases due to internal flow through the VF. Given these results, mining companies wishing to control TDS discharges may be selective and pre-test mine spoils for total S and paste SC to determine TDS-generation potential. Isolation of spoils with high-TDS release potentials (i.e. unweathered sandstones and mudstones) from water-rock contact may help improve TDS discharges. / Ph. D. / The Appalachian surface coal mining process removes rock from above a coal seam by fracturing it with explosives. The fractured rock is then used to reconstruct the original shape of the mountain, and any rock left over after that reconstruction is often placed adjacent to the mining area in landforms constructed to direct water from the mine site to a natural stream. During the mining process, the minerals in the rocks rapidly break down, and when rainwater causes the weathering products (e.g. elements such as calcium, magnesium, sulfur, selenium, and arsenic) to discharge to a stream, the aquatic ecosystem of that stream is usually affected. The objective of this study was to characterize the processes occurring in coal mining areas that ultimately influence the water quality discharged by the mine. Results indicate that many factors influence how rainwater travels through coal mining rocks and the eventual quality of waters discharged from mine rocks, and that these factors evolve over time. A study of 14-year-old mine soils indicated that the type of vegetation (i.e. trees vs. grass) planted after mining influences how water infiltrates into soils and the pathways water travels through once infiltrated. Laboratory studies of mine rocks found that many of those rocks conformed to a single mathematical model that described their elemental release patterns. The model indicated that the quality of waters discharged from mining areas is elevated above natural conditions in the initial phase after mining. Those levels appear to decline over time, but may still have long-term effects on aquatic ecosystems. Field studies of five mining-influenced streams also found that the water quality in those streams was above levels which are detrimental to aquatic ecosystems at all flow levels. It may be helpful to mining companies to test mine rocks prior to mining to determine the best location to place the rocks after mining for mitigation of water quality issues. Isolating mine rocks with the highest potentials to impact water quality may improve post-mining water quality effects.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/77528 |
| Date | 26 April 2017 |
| Creators | Clark, Elyse V. |
| Contributors | Crop and Soil Environmental Sciences, Zipper, Carl E., McGuire, Kevin J., Eick, Matthew J., Daniels, W. Lee |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf, application/vnd.openxmlformats-officedocument.wordprocessingml.document |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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