Trace element leaching from alum shale fines and red ash from Kvarntorp during a large column test

Abstract: Fuel shortage during the Second World War led to oil production in Kvarntorp, Kumla during 1942-1966 by pyrolyzing alum shale rich in pyrite, FeS2, and organic material such as kerogen. This production has led to a lot of waste laying deposited out in the open after the mining closed and has had negative environmental impact in the form of ongoing weathering and leaching of acidic water and leaching of trace elements into its surroundings. Chemical processes are still ongoing in this deposit, with temperatures reaching 700 °C on certain hotspots. Once the deposit cools down, precipitation will be able to enter the deposit and start leaching acidic water containing trace elements that will risk polluting groundwater in the surrounding areas. No one knows how many years it will take for the deposit to cool down, but it has been estimated to take at least 100 years.This study did leaching experiments on weathered fines as well as red ash in large columns while being oxygenated. Analyses consisted of ICP-MS, pH, electrical conductivity, acidity, alkalinity, and sulphate concentration.The results showed high concentrations of many valuable and potentially toxic elements in the leachates especially higher amounts of copper compared to previous studies.