About 101 papers within the field of radioecology and environmental chemistry of which 62 articles are in international peer review journals. Contributions have also been made to several reports and books including a chapter on environmental chemistry of plutonium in the new Plutonium Handbook (2. edition). Specializing on speciation (i.e. determination of physico-chemical forms) and source identification of radionuclides and trace elements using advanced techniques (e.g. synchrotron radiation based micro x-ray techniques, accelerator mass spectrometry) with emphasis on characterisation of radioactive particles in the nanometer-micrometer range. In recent years, he has also been focusing on transport, ecosystem transfer, biological responses including responses from multiple stressor exposures as well as environmental impact and risk assessments. Research director, CERAD CoE; Deputy head Section of Environmental Chemistry, MINA; Manager of the FIGARO gamma-UV irradiation facility, NMBU; Member of Advisory Board, Norwegian Nuclear Decommissioning (NND); Member of AMAP expert group on sources of radioactivity in the Arctic; Norwegian expert to Nuclear Forensics International Technical Working Group (ITWG); Board member, NorScatt, Norwegian organisation for users of synchrotron and neutron radiation infrastructures.