Development of a Rapid Assessment Method for Quantifying Carbon Sequestration on Reclaimed Coal Mine Sites

Projected climate change resulting from elevated atmospheric carbon dioxide has given rise to various strategies designed to sequester carbon in various terrestrial ecosystems. Reclaimed coal mine soils present one such potential carbon sink where traditional reclamation objectives can complement carbon sequestration. However, quantifying new carbon (carbon that has been added to soil through recent biological processes) on reclaimed mine soils have proven to be difficult due to carbonates and coal particles present in the reclaimed coal mine spoils. Visible coal particles can be removed, but the microscopic coal dust particles remain. Additionally, with the advent of carbon trading on the stock market, rapid quantification of newly sequestered carbon has proven to be elusive. The focus of this project is to assess the potential of thermogravimetric analysis as a rapid, simple and direct method for differentiating and quantifying new carbon from old carbon (carbon of geologic origin) on reclaimed coal mine sites and provide a standard procedure for determining carbon sequestered in soil sinks. Thermogravimetry is a physico-chemical technique where the weight change is measured and recorded during the incremental heating of the soil sample over a temperature range of 25 to 1000 ° C. Grass litter and limestone were used as representative organic and inorganic carbon fractions, while coal was used to differentiate the old and new carbon within the organic fraction. Recoveries of mixtures at the 95 % confidence interval were found to be 94.49 ± 4.23 % (coal) , 93.67 ± 2.11 % (litter) , and 108.88 ± 2.88 % (limestone) respectively. Each of the above components appeared as distinct separate peaks on the thermograph, with litter appearing between 260 to 390 ° C, coal 425 to 480 ° C, and limestone 640 to 740 ° C. Overlapping peaks for the organic carbon represented by the grass litter may be indicative of cellulose and lignin fractions. Ongoing work in this area is being carried out to separate such peaks which may further enhance thermogravimetric analysis as an effective method to determine new carbon and to simultaneously monitor organic matter degradation.