Monitoring of river contamination derived from acid mine drainage using airborne imaging spectroscopy (HyMap data, South-West Spain)

Kurzfassung

Imaging spectroscopy is used in this work as an essential mapping tool to monitor changes in contaminated river sediments. Multidate hyperspectral image data (HyMap) are utilized to identify spatial mineral patterns, to detect temporal changes in mineralogy and to link these changes with geochemical processes and short-term climate characteristics. River sediments contaminated by acid mine drainage are covered by crusts with variably hydrated iron sulphate. The mineralogy of the crusts and the grain size of the underlying fluvial sediments overlap. The spectra used to build up maps from HyMap data are diagnosed mineralogically with archive spectral libraries from pyrite oxidation minerals from well-known sequences of minerals. The maps compiled from hyperspectral imagery display generalized oxidation shown by the coatings over river sediments following warm and dry periods with low water level. After the wet periods, the area covered by oxidized mineralogical phases recedes in favour of hydrated sulphate. The iteration of image processing algorithms and the mineralogical and potential contamination in a geological context are described. Change detection of the mineral crusts on the river sediments by mapping using hyperspectral remote sensing data may thus enable a quantitative and qualitative environmental evaluation by the regulators.