Stability of Schwertmannite and Ferrihydrite in the Stream Waters of Imgok and Osheep Creek Polluted by Acid Mine Drainage

Abstract

The precipitation of Fe-compounds from acid mine drainage (AMD) and stream water polluted by AMD plays a crucial role in regulating pollutant migration and determining the impacts of AMD on aquatic ecosystems. It is thus essential to identify the nature of precipitates that form and to understand their stabilities in order to assess their environmental impact. This is a necessary prerequisite before an appropriate treatment program can be prepared. Various kinds of Fe-compounds have been found to precipitate from AMD, but not all of them have been investigated in detail. Schwertmannite is one of the Fe-compounds which need more investigation. Its stability constant was reported only once (Bigham et al., 1996). The purpose of this study is to determine the stability of schwertmannite and ferrihydrite as a function of the composition of the stream water from which they precipitate. Schwertmannite and ferrihydrite have been found to precipitate respectively from the stream waters of Imgok Creek and Osheep Creek in Kangwon-Do, Korea (Yu, 1996; Yu et al., 1996). Although Imgok and Osheep Creeks both drain what were once very actively operated mining areas and are polluted by AMD from the abandoned coal mines, their compositions are very different.