A unique property of mine soils is the presence of coal and carboniferous rock particles that are present in various sizes, quantities, and qualities. We present a detailed description of a 16-step method for measuring soil organic carbon (SOC) in mine soils that can successfully differentiate between pedogenic and geogenic carbon forms. The proposed method is a combination of a chemical procedure for carbonates removal, a thermal procedure for pedogenic C removal, and an elemental C analysis procedure at 900°C. Our methodology provides a means to correct for the carbon loss from the more volatile constituents of coal fragments in mine soils and another correction factor for the protected soil organic matter that can also remain unoxidized following thermal pretreatment. The performance of the 16-step method was evaluated against the Walkley-Black procedure. Both SOC estimation methods were tested on 30 different mine soil mixtures (with 6 levels of coal content ranging from 0 to10% by soil weight) carefully constructed to represent a wide spectrum of mine soils in the hard-rock region of the Appalachian coalfield.

The mean percent relative uncertainty from the true mean, PRUM(%), of SOC predictions made by the 16-step method ranged from 13 to 148% for sandstone (SS) (with true SOC of 0.082 wt%), from 11 to 41% for siltstone (SiS) (with true SOC of 0.629 wt%), from 5 to 84% for the 50:50_SS:SiS mixture (with true SOC of 0.382 wt%), and from 9 to 103% for the Jefferson soil (with true SOC of 0.811 wt%), across the spectrum of coal content levels tested. The PRUM(%) of SOC predictions made by the Walkley-Black procedure ranged from 17 to 1,003% for SS, from 2 to 122% for SiS, from 3 to 126% for the 50:50_SS:SiS mixture, and from 2 to 58% for Jefferson soil.