Wednesday, November 15, 2006

Carbon Sequestration in Reclaimed Coal Mine Lands of Wyoming.

Girisha Ganjegunte1, Peter Stahl2, and George Vance2. (1) Texas A&M University System, 1380 A&M Circle, El Paso, TX 79912, (2) University of Wyoming, Department of Renewable Resources, P.O.Box 3354, Laramie, WY 82071

Wyoming is the leading producer of coal in the U.S. and surface mining activities result in depletion of soil organic matter due to greater oxidation rates. Low soil organic C (SOC) content of reclaimed mine lands presents a great opportunity to sequester CO2 through reclamation. This research evaluated the rates and mechanisms of SOC accumulation in reclaimed coal mines of Wyoming. Soil samples were collected (0-30 cm) from mines that have been reclaimed for 6 to 20 years with cool-season-grasses (CS) and shrubs (SH). Soil samples were also collected from topsoil stockpiles that have been stored for 3 months and 16 years. Samples were analyzed for organic C using elementar analyzer and lignin concentrations in soil samples were evaluated using the alkaline CuO oxidation method followed by HPLC quantification. Results of the study indicated that SOC content of reclaimed soils increased with time. In cool season grass sites the SOC content (0-30 cm depth) increased with time from 25 Mg ha-1 in 3 months old topsoil stockpile to 33 Mg ha-1 in 20 yrs old sites. Shrub sites showed the opposite trend of declining SOC content in reclaimed sites with time, which ranged from 31 Mg ha-1 in 6 year old shrub site to 23 Mg ha-1 in 16 year old shrub site. The SOC contents of control sites (unmined areas) were greater than that of reclaimed sites (47 Mg ha-1 for CS and 48 Mg ha-1 for SH). Lignin contents of SOC in reclaimed sites were significantly greater than that of control indicating there has been an accumulation of recalcitrant organic C compounds in reclaimed sites. Results our study indicated the greater C sequestration potential of reclaimed mine lands and that the biochemical mechanism can be the major C stabilization process in the reclaimed mine lands of Wyoming