BUDGETING SOIL CARBON IN THE CLEAN COAL DISCUSSION: ELEMENTAL AND ISOTOPIC MEASUREMENTS AND MODELING OF SOIL CARBON UPTAKE ON RECLAIMED MINING SITES

While recent research has focused on the use of carbon capture and sequestration technology feasibility, less focus has been placed upon terrestrial carbon storage affected by coal mining in the context of the clean coal debate. Recent research has shown that the initial disturbance of soil and above-ground carbon pools caused by surface coal mining methods can produce a significant carbon loss from the terrestrial ecosystem, thus increasing the coal carbon footprint of coal. However there is a lack of information regarding the uptake of CO₂ on reclaimed mining sites during re-growth and re-establishment of the soil carbon profile. This study was conducted in order to investigate carbon sequestration processes and rates in reclaimed surface coal mine lands in the Southern Appalachian forest region. Five reclaimed mining sites varying in age since reclamation (0, 2, 6, 8 and 10 years) were sampled to a depth of 50 cm to determine the corresponding carbon densities. In addition, nearby undisturbed forest sites were sampled to determine baseline carbon data for the region. In undisturbed forest sites, the carbon content decreases gradually with depth while nearly all soil organic carbon was stored in the first 10 centimeters for the reclaimed soils. Improved estimates with respect to past studies of the carbon density at each site were calculated by un-mixing soil organic carbon and geogenic organic carbon using carbon stable isotopes and a correction for rock fragments at the sites. Carbon densities for the 0, 2, 6, 8 and 10 year sites were 0.73, 1.1, 8.0, 6.3 , and 7.0 Mg C ha^-1, respectively, as compared to 91 Mg C ha^-1at the control sites. The temporal variation of soil carbon was modeled using a first order kinematic equation and it was found that carbon sequestration reached a value within 5% of baseline data in 330 years. Analysis of carbon elemental and isotopic data suggested that soil carbon turnover increases with the age of reclaimed mining site. Further analysis of short and long-term ecosystem carbon budgets is needed for reclaimed mining soils in order to better model their carbon sequestration potential. Understanding the long-term progression of carbon budgeting in reclaimed mine soil can lead to more effective reclamation guidelines and cleaner coal production.