Utvärdering av kalkbehandlad sulfidjord i Ersmark, Umeå

Sammanfattning: Acid sulfate soils cover a relatively large area of Sweden, especially the coast along Gulf of Botnia. As these soils in contact with oxygen they start to oxidize and the sulphide is converted to sulphate, leading to a strong acidification. Today, these acid sulfate soils often end up on landfills, which is not a sustainable solution as it is both costly and there is a risk of leakage. A company based in Umea has developed a method for neutralizing acid sulphate soil with hope that it can be reused as plant soil, by adding sand and calcium as well as organic matter. At present, the process is only half-finished as the organic matter is not yet added. This study determined how the treatment worked so far, how much sulphide and neutralizing potential remains in the soil, as well as a number of metals and nutrients commonly and preferably found in plant soil. The treated sulfide soil was compared with a plant soil nearby, along with comparison of data from four different studies elsewhere on sulphide soil and results from samples taken before the sulphide soil was treated. Results show that pH value was higher than before the treatment and total sulfur content had decreased, but is still twice as high compared to the plant soil. Sulphide is still found in the soil, but also a fair amount of calcium carbonate, which shows that the reaction is not completed but that the soil has the potential to be further neutralized. Metal content in the treated sulfide soil is similar to the plant soil. The humus content is at 1.3 % and lower than recommended. Depending on area of use the humus content has to increase, more or less. Based on the results of the analyzes, the treated soil cannot be used as plant soil at the present time. This because of the organic matter that has not yet been added, and that there is still sulphide left in the soil.