Browsing by Author "Männistö, Theo"

The traditional method for identifying sulfate soils has been the incubation method, which typically takes 9-19 weeks. However, in collaboration, the Finnish Environment Institute (SYKE), Geological Survey of Finland (GTK), and Åbo Akademi developed a faster hydrogen peroxide oxidation method for identifying sulfate soils and assessing acidity potential. This method allows for sulfate soil identification and acidity potential estimation in just a few hours. The hydrogen peroxide oxidation method was used to identify sulfate soils in the Helsinki region and to evaluate the method. The study areas included the Sunnuntaipalsta-field area in Malmi, the area associated with the relocation of Gasgrid’s gas pipeline in Pihlajamäki, and the Hermanninranta- Kyläsaari area. Sulfate concentrations determined by the oxidation method were compared with concentrations obtained through water extraction at the Helsinki geophysical, environmental and mineralogical laboratories (Hellabs) of the University of Helsinki's Department of Geology and Geophysics, and acid extraction at ALS Finland Ltd. In Malmi, the method worked well and reliably, indicating naturally acidified soil with relatively low sulfur concentrations. Deeper layers revealed potential acidic sulfate soil materials. In Pihlajamäki, the method was effective, identifying clear potential acidic sulfate soils even with samples consisting of clay fillings. Challenges arose in the Hermanninranta-Kyläsaari area due to contaminated fill soils with high pH values and various hydrocarbons. The lower layers of the samples were rich in organic matter (LOI > 10%), causing the hydrogen peroxide oxidation method to overestimate sulfate concentrations, resulting in deviations with both acid and water extraction results. Based on the results, the hydrogen peroxide oxidation method performs most reliably when loss on ignition (LOI) is < 10% and the pH change (ΔpH) after oxidation is less than 5 units. The method could be a valuable addition to soil investigations conducted by the City of Helsinki's construction services public enterprise, Stara, in their Street and ground laboratory. The method is effective and enables the rapid identification of potential acidic sulfate soils.