THE ROLE OF THERMAL-CONVECTION IN RESUPPLYING O2 TO STRIP COAL-MINE SPOIL

Oxygen has long been recognized as a control on the acid-generating re actions which produce acid mine drainage, and great effort has been ma de to reduce oxygen recharge to mine spoil. To investigate O2 availabi lity and the role of thermal convection in O2 transport in mine spoil, spoil temperature, O2, and CO2 concentrations of spoil gas were measu red monthly throughout the entire thickness of mine spoil for 1 year a t an abandoned strip mine in Clearfield County, Pennsylvania. O2 conce ntrations deep inside mine spoil were found to be 18% or higher, despi te active pyrite oxidation. The O2 inside this mine spoil had not been lowered to a level that limited the generation of acid mine drainage. Temperature surveys showed thermal anomalies, which appear to result from heat generated by pyrite oxidation reactions. The field data and a simple model show that thermally induced air convection can be a dom inant process maintaining high O2 concentration in deep mine spoil.