"The great “riverine input-output paradox” is that even though the inputs of organic pollutants in rivers are enormous by point and non-point sources, the levels of pollutants in rivers are moderate and the final amount and impact of organic pollutants that reach the sea is small in comparison to other processes transporting pollutants to the marine environment Therefore, there is a need to study the degradative potential of rivers (and other sinks such as volatilization) in order to understand and predict the role that rivers play in the biogeochemical cycling of organic pollutants at regional scale. The main aim of the research proposed here is to contribute in the rise of knowledge about the degradative potential of rivers as driver of environmental fate and transport of organic pollutants during longitudinal transport. Specifically, it will contribute to shed the light on the issue of transformation products and abiotic and biotic degradation in rivers using selected representative organic pollutants covering a wide window of physical chemical properties in microcosm experiments in the laboratory and in the field . The impact of transformation products has been more or less ignored in terms of modelling. Work is required to develop the appropriate modelling strategies to assess potential risks and role of these substances. This research will contribute to the knowledge of the impact of organic pollutants in riverine systems and provide modelling tools to predict the ultimate fate and transport of these pollutants to other media (seas and atmosphere)."