Abstract
Remote-sensing techniques offer an efficient alternative for mapping mining environments and assessing the impacts of mining activities. Airborne multispectral data in the thermal region and hyperspectral data in the optical region, acquired with the Airborne Hyperspectral Scanner (AHS) sensor over the Sokolov lignite open-pit mines in the Czech Republic, were analyzed. The emissivity spectrum was calculated for each vegetation-free land pixel in the longwave infrared (LWIR)-region image using the surface-emitted radiation, and the reflectance spectrum was derived from the visible, near-infrared and shortwave-infrared (VNIR–SWIR)-region image using the solar radiation reflected from the surface, after applying atmospheric correction. The combination of calculated emissivity, with the ability to detect quartz, and SWIR reflectance spectra, detecting phyllosilicates and kaolinite in particular, enabled estimating the content of the dominant minerals in the exposed surface. The difference between the emissivity values at λ = 9.68 µm and 8.77 µm was found to be a useful index for estimating the relative amount of quartz in each land pixel in the LWIR image. The absorption depth at around 2.2 µm in the reflectance spectra was used to estimate the relative amount of kaolinite in each land pixel in the SWIR image. The resulting maps of the spatial distribution of quartz and kaolinite were found to be in accordance with the geological nature and origin of the exposed surfaces and demonstrated the benefit of using data from both thermal and optical spectral regions to map the abundance of the major minerals around the mines.
Highlights
Mining has a wide range of impacts from processes such as the generation of acid tailings, metal contaminants, and air pollution caused by smelting activities, leading to soil erosion, water pollution, vegetation disturbance, and habitat degradation
An emissivity feature was observed in the spectrum of each land regions of interest (ROIs) between λ = 8.31 μm and λ = 10.14 μm
The emissivity spectrum of each land pixel in the longwave infrared (LWIR) image was calculated and the reflectance spectrum of each land pixel was derived from the VNIR–SWIR
Summary
Mining has a wide range of impacts from processes such as the generation of acid tailings, metal contaminants, and air pollution caused by smelting activities, leading to soil erosion, water pollution, vegetation disturbance, and habitat degradation. The current study makes use of airborne multispectral LWIR data, along with airborne hyperspectral SWIR data, to assess the mineral content in exposed vegetation-free rocks and soils ( land) in a lignite mining site in the Sokolov Basin, Czech Republic, as a case study. Mapping the distribution of the dominant minerals in the area—quartz and kaolinite—is relevant for the management or monitoring of mining sites, as well as for assessing the quality of the material used for reclamation. Whereas the hydroxyl-bearing mineral kaolinite, as well as other phyllosilicates, can be detected in the SWIR spectral region using the absorption feature at around 2.2 μm [25,26], quartz can only be mapped using the LWIR spectral region
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