Predicting total dissolved solids release from central Appalachian coal mine spoils.

Area of Science:

• Environmental Science
• Geochemistry
• Water Quality Management

Background:

• Surface coal mines in Appalachia face pressure to reduce total dissolved solids (TDS) in discharge due to impacts on aquatic life.
• Specific conductance (SC) is a reliable indicator for TDS, with proposed benchmarks for instream water quality between 300-500 μS cm⁻¹.
• Coal mine discharges often exceed 1000 μS cm⁻¹.

Purpose of the Study:

• To assess how rock type and weathering affect SC leaching from mine spoils.
• To correlate laboratory leachate SC with field discharge SC.
• To identify rapid laboratory analyses for predicting SC in overburden materials.

Main Methods:

• Laboratory unsaturated column leaching experiments with 39 overburden materials.
• Correlation of column leachate SC with static lab parameters (total-S, saturated paste SC, neutralization potential).
• Comparison of lab data with field leaching and valley fill discharge SC data.

Main Results:

• Leachate SC is significantly influenced by rock type and pre-disturbance weathering; fine-textured, non-weathered strata and high-sulfur black shales yield higher SC.
• Laboratory columns simulated field SC decay trends within 5-10 leaching cycles.
• Initial peak SC is reliably predicted by saturated paste or 1:2 spoil:water SC tests (R² > 0.850).

Conclusions:

• Rock type, sulfur content, weathering, and rapid SC lab measurements can accurately predict overall TDS release risk.
• While initial SC can be predicted, long-term SC behavior requires further investigation.
• Understanding spoil characteristics is crucial for managing TDS pollution from coal mining.