The MAELSTROM project aims to test and evaluate innovative technologies for the removal of marine litter in different coastal environments, while also assessing their impact on the ecosystems in selected demo sites and evaluating the economic and societal benefits of the MAELSTROM solutions within local economies. The Deliverable 2.1 - Report on the characterization of major sources of marine litter and macro-plastic in the demo sites, aimed to create the baseline knowledge about marine litter sources both land and sea-based. An overall review on marine litter sources, in particular macro-plastic, was performed at European level. The review was based on information available from literature and the results served as reference to frame the results of the specific literature surveys focused on the two demo sites. In the two demo sites, i.e the Lagoon of Venice and the North Western coast of Portugal, detailed studies focused on the identification and mapping of the sources of macroplastic were analysed. In particular, information about mass flow and about the characteristics of the macro-plastics was collected to identify their potential sources and pathways. The survey was performed through the consultation and analysis of existing databases on marine litter data on the sea floor, rivers and beaches. This allowed to organize the marine litter data available for demo sites upon spatial layers to support the comparison with the applied dispersal numerical models. The collected information and data will feed the numerical models run in T2.2.