Application of Imaging Spectrometer Data in Identifying Environmental Pollution Caused by Mining at Rodaquilar, Spain

The Rodaquilar mining area in southern Spain has been mined for gold for an extensive period, most recently in the 1940s and 1950s. This activity has resulted in waste rock and tailings being dispersed from the mine workings down to a large tailings dump and then along a river valley eventually reaching the sea. This tailings dump material consists of a variety of ferruginous materials that often contain trace elements that are environmentally harmful and possibly toxic. These ferruginous materials have distinctive spectral features which make them amenable to detection and mapping by airborne imaging spectrometer data. The dispersion of the tailings material was studied using two semiquantitative techniques, matched filtering and linear spectral unmixing and qualitative methods using band ratios and the variation in strength of spectral features. The distinct ferruginous mineral phases resolved by these methods were then compared to laboratory reference spectrum using qualitative analysis of the spectral profiles and two quantitative techniques, spectral angle mapping and cross correlogram spectral matching. The distribution of the ferruginous materials identified from the imaging spectrometer data supports the results of laboratory experiments on the dependence of the formation of iron species on their geochemical and physical situation.