Old Mountains, New Nutrients: Mountaintop Mining's Impact on Watershed Scale Nitrogen Export
Abstract
Mountaintop removal coal mining with valley fills (MTM-VF) is a form of coal mining common in the Central Appalachians that uses explosives and draglines to uncover shallow seems of coal. The coal residues and overburden are disposed of into adjacent valleys forming valley fills up to 200m thick. The large quantities of unconsolidated rock increase watershed storage potential and vastly increase rates of rock weathering via sulfuric acid generated by coal residues. This leads to high concentrations of coal and rock derived ions in receiving surface waters. Here we report on baseflow and storm samples and continuous hydrologic and specific conductivity data to investigate how MTM-VF and valley fills of various ages alter the flux and timing of nitrogen export in headwater catchments. Annual NO3-N flux from the mined Laurel Branch (LB) headwater stream (95% mined, 68 ha) was 21.1 kg NO3-N/ha/yr. This flux was more than 70x higher than the Rich's Branch (RB) reference catchment (0% mined, 118 ha). Mean baseflow NO3-N concentrations in LB were 2.65 ± 0.32 mg/l (95% CI), significantly higher than the 0.11 ± 0.02 mg/l (95% CI) observed at RB. Concentrations at LB, which was reclaimed five years ago, were intermediate relative to the actively mined Mueller's Branch (5.06 ± 1.59 mg/l) and Ballard Fork (1.73 ± 0.80 mg/l), which was reclaimed over twenty years ago. Although annual NO3 flux in LB is within the range of those observed in other abrupt landscape disturbances, the persistence of elevated NO3 levels decades after disturbance differentiates MTM-VF from other landscape disturbances. There are several possible explanations for this elevated NO3-N export. Here we explore the potential for mining associated explosives, fertilizer, soil and buried organic material mineralization, N fixation, and rock weathering derived N to explain this excess nitrogen.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.H41G..03B
- Keywords:
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- 1803 Anthropogenic effects;
- HYDROLOGYDE: 1804 Catchment;
- HYDROLOGYDE: 1860 Streamflow;
- HYDROLOGYDE: 1871 Surface water quality;
- HYDROLOGY