Occurrence, leaching, and mobility of major and trace elements in a coal mining waste dump: The case of Douro Coalfield, Portugal

The coal mining residues from past activities in the Douro Coalfield are emplaced many dumps near areas, causing substantial environmental impacts. This study aims to contribute investigation of impacts caused by disposal residue through determination geochemical composition waste materials collected at 3 – 15 m depth, and water-leachable fraction produced percolation these inside dump. elements with higher concentration leachates Ca, Cd, Co, Mg, Mn, Na, Ni, S, Zn, indicating that they most easily leached accessible for mobilization into environment. presence is principally attributed their occurrence as water-soluble ions clays sulphides affected natural weathering conditions, which promotes breakdown exchangeable ions. classified acid high-metal. Natural leaching São Pedro da Cova dump principal paths chemical be percolated mobilized environment, posing risk soils, waters ecosystems surrounding areas.