Watershed wash-off of atmospherically deposited radionuclides: review of the fluxes and their evolution with time

Radionuclide transport with water from contaminated watersheds is an intermittent flux – also called watershed wash-off – which causes radionuclide redistribution in terrestrial ecosystems, and more critically radionuclide delivery to downstream waterbodies. Mean wash-off fluxes and their evolution with time have been generally quantified with transfer functions, which can be seen as transfer factors varying with time. But unfortunately the published quantifications rely on many analytical formulations for the transfer function. This paper aims at unifying the heterogeneous information concerning radionuclide wash-off. A generic transfer function model was proposed. Published wash-off quantifications were gathered in a database and converted within this new framework. This extensive review covered various radionuclides, source terms, processes, time and space scales reported in the literature since 1960. It demonstrated the feasibility of a generic wash-off model. Intervals of variations for the introduced coefficients were summarised and the influence of wash-off conditions were discussed. In some cases, the influence of wash-off conditions should be clarified to propose narrower parameter intervals for practical assessments.