Leaching Test of Sulphide-Bearing Rock Masses

In urban development projects, site preparation often requires excavation, which generates rock masses. In Stockholm Royal Seaport, rock masses from metro expansion that may contain sulphide and affect the environment through leaching are being reused.

Rock masses will be reused to create new land and habitats in the water. If these masses contain sulphide minerals, they can oxidize when in contact with air and water, which may lead to acidification of surrounding aquatic environments. To date, leaching risks are primarily assessed in acidic conditions, such as lakes. There is a knowledge gap regarding use in brackish or salt water.

Objective and goals

The purpose of the research project 'Recycling of Sulphide-Rich Construction Rock for Reef Building - Long-term Leaching Test in Aquatic Environment' is to study whether iron sulphate leaching occurs in water from the Baltic Sea and Lake Mälaren. Should the study demonstrate that no leaching occurs, the rock masses can be reused instead of being transported to landfill.

The aim is to contribute new knowledge about how sulphide-rich rock can be used for construction in water.

Among other things, the study will examine what chemical changes occur in the water and what environmental risks this entails. Tests are being conducted in Loudden and at Lake Mälaren. In Loudden, a basin is filled with crushed rock where Baltic Sea water is pumped in. Continuous measurements of pH value, ionic strength, sulphide content and elements in the rock are then taken. Weather impact will also be studied.

Results and Experiences

The investigations are ongoing and the final report will be presented in spring 2026.