‘Down to the river’: amount, composition, and economic sector of litter entering the marine compartment, through the Tiber river in the Western Mediterranean Sea

Land-based activities are, undoubtedly, the main source of marine litter, particularly in a highly populated closed sea basin, such as the Mediterranean Sea. Rivers, consequently, act as a pathway of mismanaged waste to the sea. While quantification of inputs is a difficult task, the assessment of abundance, composition trends and baselines, and the identification of sources and main sectors producing marine litter are of crucial importance to support the ability of policy makers to improve waste reduction measures. For this reason, the Joint Research Centre (JRC/RIMMEL) coordinated a network of several research bodies that monitored floating litter (> 2.5 cm) from fixed observation points located on rivers near the sea using the same systematic research protocol. In Italy, one of the surveyed rivers was the Tiber, the third longest river on the peninsula, which after running through the city of Rome divides into two branches before flowing into the Tyrrhenian Sea. Results of 1 year of monitoring, September 2016–August 2017, highlight that 82% of the floating items were plastic and belong to the food and cosmetic sector, and it was estimated that 85.4% (± 9.4) of litter items get into the sea each hour from the Tiber river canal in Fiumicino, of which approximately 30% were already fragmented.