Microplastics and microfibers contamination in the Arno River (Central Italy): Impact from urban areas and contribution to the Mediterranean Sea

Fluvial ecosystems are among the main drivers of microparticles (MPC) in the form of both synthetic polymers (i.e. microplastics; MPs) and natural-based textile fibers (MF TEX ) to the seas. A wide dimensional range of MPC (5 to 5000 μm, hereafter MPC TOT ) were investigated for the first time in the Arno River waters, one of the principal rivers of Central Italy, crossing a highly anthropized landscape. Fluxes of MPC TOT discharging to the Mediterranean Sea, one the most polluted Sea worldwide, were estimated as well. A specific sampling and analytical protocol was set up to distinguish between microplastics (MPs) and natural-based textile fibers (MF TEX ) contribution for MPC larger than 60 μm (MPC >60 ), and investigate MPC smaller than 60 μm (MPC 99 % of total particles found and whose abundance increases inversely with particle size. The MPC >60 fraction (60 . The metropolitan area of Florence was identified as an MPC TOT hotspot as a consequence of the intense urbanization and possibly of over-tourism phenomenon affecting the city. The Arno River discharges approximately 4.6 × 10 15 MPC TOT annually to the Mediterranean Sea. Fluxes are highly dependent on the seasonality, with a MPC TOT delivery of 2.4 × 10 13 particles/day and 1.2 × 10 12 particles/day during wet and dry season, respectively. The total mass of discharged MPC TOT is estimated at about 29 tons/year (t/y); the MPC >60 fraction amounts to about 8 t/y, and MF TEX to about 1 t/y. • Microparticles (MPC) contamination of the Arno River waters is highlighted. • μ‐FTIR + fluorescence microscopy allows the investigation of a wide MPC size range. • MPC >60 are mainly textile fibers; MPC <60 are more abundant and easily mobilised. • The City of Florence is identified as MPC hotspot. • Meteorological forcing inland influences MPC contribution from the river to the sea.