Abstract

At a 50-year-old coal mine drainage barrens in central Pennsylvania, USA, we evaluated the biogeo- chemistry of acidic, Fe(III)oxy(hydr)oxide precipitates in reclaimed plots and compared them to un- treated precipitates in control areas. Reclaimed plots supported successional vegetation that became established after a one-time compost and lime treatment in 2006, while control plots supported bio- logical crusts. Precipitates were sampled from moist yet unsaturated surface layers in an area with lateral subsurface flow of mine drainage above a fragipan. Fe(II) concentrations were three- to five-fold higher in reclaimed than control precipitates. Organically bound Fe and amorphous iron oxides, as fractions of total Fe, were also higher in reclaimed than control precipitates. Estimates of Fe-reducing and Fe- oxidizing bacteria were four- to tenfold higher in root-adherent than both types of control pre- cipitates. By scaling up measurements from experimental plots, total Fe losses during the 5-yr following reclamation were estimated at 45 t Fe ha 1 yr 1.