METAL TRANSPORT IN A STREAM POLLUTED BY ACID-MINE DRAINAGE - THE AFONGOCH, ANGLESEY, UK

Sampling of the Afon Goch over a 14-month period revealed maximum diss olved Fe, Al, Mn, Cu and Zn concentrations of 259, 167, 49, 60 and 42 mg dm-3, respectively, and pH as low as 2.3, making it one of the most metal- and acid-contaminated streams in the UK. The river produces pa rticulates by precipitation of ferrihydrite, due to the entry of near- neutral tributary waters, under all discharge conditions. Consequently , metal transport in this stream is dominated by processes different f rom those in less contaminated streams. The stream acts as a sink for contaminants, except under high discharge, when accumulated metals are flushed from the system. The implications of these observations for t he monitoring and management of streams polluted by acid mine drainage are discussed,