Identifying acid mine-drainage pollution at Captains Flat, NSW, using airborne HYMAP data

The Captains Flat mine in southern NSW, Australia, produced significant quantities of base metal ore over a period of 80 years, ceasing in 1962. Considerable funds were spent in the mid 1970s on rehabilitation of the tailings dumps and workings. Despite this, acid groundwaters sourcing from the mine contain pollutant metals and continue to impact the ecology including vegetation, macro-invertebrates and fish. An airborne HYMAP hyperspectral survey was flown over the mine area to detect and monitor acid-mine drainage (AMD) and environmental effects. Minerals that precipitate from add waters draining from mine areas are of interest for remote sensing since they indicate the source, extent and conditions of environmental pollution. Precipitates are iron oxyhydroxides, oxyhyroxysulfates and sulfates. Spectral and XRD studies of mine drainage areas identified goethite, ferrihydrite, schwertmannite, natrojarosite, hydronium jarosite, gypsum and other sulfates. The most important of these are schwertmannite and ferrihydrite, which have high metal adsorption. Analysis of HYMAP data showed that AMD components can be detected as they enter the environment. This was valuable in identifying seepage areas that need to be remediated