Mining waste is often sulfidic which oxidizes if it comes into contact with oxygen and water. This can cause harmful metals to be released and transported to surface- and groundwater, which can lead to environmental damage.
"This fall I have installed instruments to evaluate a remidiation of a waste rock dump in a test area at the Näsliden mine in Västerbotten," says Susanne Nigéus.
A common remidiation method is to cover the waste with a compacted layer of clayey till. This prevents water and oxygen from reaching the mining waste, which prevents oxidation. Since 2009, green liquor dregs, a residual product from the pulp industry, have been investigated at Luleå University of Technology as an additive to improve the natural till if the clay content is not sufficient.
"Our installed instruments measure oxygen concentration, soil moisture and temperature. The purpose is to find out how much water and oxygen reaches the waste under the dirt layer and how frost penetrates through the coverage," says Susanne Nigéus.
A desirable result would be if it appears that the sealing layer is near water saturated and that the oxygen concentration is near zero. This would minimize the sulfide oxidation and leaching of metals to the ground and surface water. The first results of the experiment are expected in autumn 2018.