ACCELERATED WEATHERING OF SANDSTONE WITH A SOXHLET EXTRACTOR

Simulated accelerated weathering was conducted using a Soxhlet extractor at 105^oC with aqueous reflux solution to simulate nature leaching in the area. The leaching residues and the leachates were analyzed by ICP-MS analysis to determine how the refluxes are affecting the composition of sandstone sample and leachate produced.

The ICP-MS method can detect and analyze up to 46 elements. As determined in leaching residues, all ofNb, P, the chemical elements are essentially unchanged within analytical errors up to four times of refluxes. However, the analyses of leachate showed that Al, Ba, Ca, Cd, Ce, Cu, Fe, Mg, Mn, Na, Ni, Pb, Rb, S, Sr, and Zn are affected by the repeated refluxes. Elements Ag, As, Be, Bi, Cs, Ga, Hf, In, La, Li, Lu, Nb, Sb, Sc, Se, Ta, Tb, Te, Th, Tl, U, V, Y, Yb, and Zr are close to detection limits. Systematic changes were observed in Mn and Zn. As determined with environmental scanning microscope. Manganese is found largely in calcareous matrix and Zn in pyrite. The experiments with increasing number of refluxes suggest that the dissolution of calcareous matrix is continuing after four refluxes. However, the leaching process of pyrite appears to slow down and reach an equilibrium value after four refluxes.

The experiments implies that calcareous matrix in sandstone debris in covering material of solid waste disposal site could still remain as a source of trace elements while weathering of pyrite stops to become a source of trace elements in leachate..