Integration Of Drone-Borne Hyperspectral And Photogrammetric Techniques To Investigate Surface Changes Induced By Acid Mine Drainage. A Case Study Of Litov In The Sokolov Mining District, Czech Republic
Tumwet, Faith Chebet (1); Jackisch, Robert (2); Zimmermann, Robert (2); Gloaguen, Richard (2)
1: Hochschule für Technik und Wirtschaft Dresden, Germany; 2: Helmholtz-Zentrum Dresden-Rossendorf, Helmholtz Institute Freiberg for Resource Technology
This study seeks to investigate the effects acid mine drainage (AMD) has on a drainage channel leading acidic water (pH 2 – 3) from a recultivated sulfide-rich tailings dam and spoil heap to a pit lake located in Litov in the coal mining district Sokolov, Czech Republic. The main aim is to examine surface changes induced by AMD to aid in the design and modification of the drainage channel and the tailings dam wall.
The objective is achieved by analyzing drone-borne multispectral and hyperspectral datasets acquired from a 2016 research representing the initial topography of the area available at Helmholtz Institute Freiberg for Resource Technology (HIF), against drone-borne multispectral and hyperspectral datasets gathered in 2018 reflecting the present topography. Field and flight campaigns during the 2016 research were accompanied by pH and X-ray diffraction (XRD) analysis for ground truth, while pH, electrical conductivity, dissolved oxygen, and sulfate concentrations were collected to supplement the 2018 campaigns.
The hyperspectral data enabled the mapping of the extent and distribution of iron-bearing minerals jarosite, goethite, and hematite which are mostly occurring in acidic environments. The classification methods employed, spectral angle mapper (SAM) and band ratios, suggest a decrease in the magnitude of jarosite and an increase in precipitated goethite.
3D georeferenced surfaces were constructed through Structure-from-motion (SfM- Stereophotogrammetry) photogrammetric techniques by utilizing multispectral data, in the form of RGB images, and global navigation satellite systems (GNSS). Surface changes were evaluated using the cloud-to-cloud distance algorithm revealing morphological modifications. This has led to an array of weathered sedimentary landforms developed upon the slopes as well as depositional features accelerating precipitation and hydrolysis of goethite during low flow in the drainage channel.
The erosive characteristics of the iron-bearing secondary minerals and a connection to hydrological processes accelerate the acidity and metal leach-ability posing a risk to the environment while escalating modifications of its landscape.
The proposed remediation action is the adaptation of the sloping topography to control surface runoff.