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

Abstract

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_<60) as well. Results suggest extreme MPC_TOT contamination all along the river (up to 6 × 10⁴ particles/L), strongly driven by MPC_<60, which account for >99 % of total particles found and whose abundance increases inversely with particle size. The MPC_>60 fraction (<0.5 % of MPC_TOT) highlighted a predominance (76 % of the total) of MF_TEX and synthetic polymers microfibers (e.g., PET) suggesting strong contributions from laundry effluents. Specifically, MF_TEX represent around 70 % of all MPC_>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 × 10¹⁵ MPC_TOT annually to the Mediterranean Sea. Fluxes are highly dependent on the seasonality, with a MPC_TOT delivery of 2.4 × 10¹³ particles/day and 1.2 × 10¹² 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.