Laboratory Investigations of Weathering of Soils from Mammoth Mountain, CA, a Naturally CO2-Impacted Field Site

The potential impacts of CO2 leakage from a natural subsurface reservoir on soil and water quality were studied. Field measurements of soil pore CO2 concentrations and visual inspection of plants at Mammoth Mountain, CA, allowed the demarcation of tree-kill and non-tree-kill zones, with CO2 concentrations >100,000 ppm and ∼1,000 ppm, respectively. Soils collected from six sites along a transect stretching from the center of the tree-kill zone to an equidistant point into the non-tree-kill zone were analyzed for surface area and organic carbon content. Batch and column leaching tests were conducted to determine the extent of weathering induced by the presence of CO2 in the aqueous solution. Soils deep into the tree-kill area exhibited significantly higher surface areas (10.67 m2/g vs 2.53 m2/g) and lower organic carbon content (9,550 mg/kg vs 35,550 mg/kg). Batch results indicated that lower pH values (∼2) released higher concentrations of Mg, Si, Fe, and As, while, for soils in the tree-kill zone, longer-...