Federal Office of Public Health 1 article published in JoVE Engineering Speciation and Bioavailability Measurements of Environmental Plutonium Using Diffusion in Thin Films Ruslan Cusnir1, Philipp Steinmann2, Marcus Christl3, François Bochud1, Pascal Froidevaux1 1Institute of Radiation Physics, Lausanne University Hospital, 2Federal Office of Public Health, Bern, Switzerland, 3Laboratory of Ion Beam Physics, ETH Zurich The technique of diffusive gradients in thin films (DGT) is proposed for speciation studies of plutonium. This protocol describes diffusion experiments probing the behavior of Pu(IV) and Pu(V) in presence of organic matter. DGTs deployed in a karstic spring allow assessment of the bioavailability of Pu.