The Gateway Project "Mitigation of trace element concentration by adding organic carbon (Mitracarb)" is conducted at GEUS - Geological Survey of Denmark and Greenland in Copenhagen and Aarhus. Cooperation partners are Dr. Birgitte Hansen, Dr. Rasmus Jakobsen and Dr. Hyojin Kim. The aim of this project is to determine the process which mitigates trace element concentrations by adding organic carbon. This observation of mitigation of trace element concentrations was made in previous studies where organic carbon was originally used for enhanced nitrate reduction. The change in pH and redox potential was initially expected to lead to a mobilization of trace elements. However, the exact process responsible for the reduction of trace element concentrations could not be identified with the previous analyses. The different trace elements presumably interact differently with different minerals and surfaces in the sediments and this interaction can be clarified via sediment extractions. With a sequential extraction procedure, that mobilizes trace elements from different surfaces and minerals in the sediment, the binding type and processes for the different trace elements can be determined.