Asbestos fibres introduce trace metals into streamwater and sediments

Based on a case study in the Sumas River, it is demonstrated that asbestos fibres, which were introduced by a massive landslide, have altered the water quality and sediment conditions in the downstream section of the river. Asbestos fibres, because of their small size, are readily transported and resuspended i in stream systems. Associated with the fibres are high quantities of Ni, Cr, Co and Mn which occur as contaminations and isomorphic substitutions in most asbestos materials. A direct link between discharge, asbestos fibre and Ni concentrations was demonstrated in the water. Trace metal values in the sediments decrease with distance from the point source but the concentrations 20 km downstream of the slide are still significantly higher than levels at a control station unaffected by the slide. Asbestos fibres leach in acid media, and Mg and trace metals are removed. The process and rates were illustrated on the basis of laboratory experiments using organic acids. Since the pH in the streamwater is decreasing from 8.4 to 7.1 in the downstream direction, trace metals release is of concern.