The Role of Redox Processes in Shaping Soil Water Quality of Reclaimed Mine Soils

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Amir Hass, Fatima Irfan, Robert Cantrell, Jeff Skousen

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Surface mine reclamation practices affect headwater soil and water quality. Such practices, especially in steep-topography, tend to incorporate rock spoils of different weathering stages (e.g. saprolite, blast-rock fragments) with the salvaged soil for further use as topsoil-replacement material during reclamation. Such material alters composition and properties that otherwise ubiquitous to native soils, affecting soil biogeochemical processes and outcomes. In this study, we attempted to elucidate the governing processes affecting soil water quality under such practices. Sites in southern WV, USA, reclaimed using sandstone spoils of different weathering stages, placed at different compaction levels, were instrumented with soil water sampling devices, 12 years after reclamation. Water samples were collected weekly during a 3-year study and analyzed for metals content, ionic composition, total alkalinity, and dissolved organic carbon in addition to in-situ measurement of dissolve oxygen, pH, temperature, total dissolved solids (TDS), and redox potential. Episodes of high TDS (exceeding USA-EPA regulatory threshold of 300 ┬ÁS cm-1) were associated with low redox potential (Eh < 300 mV) and with pH shift to circumneutral values. Wide within-season fluctuation was observed in all measured parameters. Ubiquitous to mining environment, present of sulfate (as well as that of other terminal-electron acceptors; TEA) showed, in successive incubation studies, to affect soil solution redox potential. The results are discussed in the context the limited pools and ability of reclaimed mine soils to buffer changes in moisture, pH, redox, etc., pointing to potential vulnerability amid expected increase in frequency and intensity of extreme weather events.

Resource Type:
Conference Presentation, SER2021

Pre-approved for CECs under SER's CERP program