About 106 papers within the field of radioecology and environmental chemistry of which 67 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). Main expertise is speciation (i.e. determination of physico-chemical forms) and source identification of radionuclides and trace elements using advanced techniques (e.g. electron microscopy, synchrotron radiation based micro- and nano-focused x-ray techniques, accelerator mass spectrometry) with emphasis on characterisation of environmental particles including microplastic and radioactive particles in the nanometer-micrometer range. He is also focusing on environmental impact and risk assessments involving environmental transport and ecosystem transfer modelling as well as biological responses including from multiple stressor exposures. Research Director, CERAD CoE; Deputy Head of Section of Environmental Chemistry, MINA; Manager of the FIGARO gamma-UV irradiation facility, NMBU; Deputy Chair of Faculty Research Committee, MINA, NMBU; Member of Advisory Board, Norwegian Nuclear Decommissioning (NND); Member of AMAP expert group on sources of radioactivity in the Arctic; Norwegian expert to IAEA CRP on Transfer of radionuclides in semi-arid and arid environments and Nuclear Forensics International Technical Working Group (ITWG); Board member, NorScatt, Norwegian organisation for users of synchrotron and neutron radiation infrastructures.