Abstract
Microplastic research has mainly concentrated on open seas, while riverine plumes remain largely unexplored despite their hypothesized importance as a microplastic source to coastal waters. This work aimed to model coastal accumulation of microplastic particles (1–5 mm) emitted by the Po River over 1.5 years. We posit that river-induced microplastic accumulation on adjacent coasts can be predicted using (1) hydrodynamic-based and (2) remote sensing-based modelling. Model accumulation maps were validated against sampling at nine beaches, with sediment microplastic concentrations up to 78 particles/kg (dry weight). Hydrodynamic modelling revealed that discharged particle amount is only semi-coupled to beaching rates, which are strongly mouth dependent and occur within the first ten days. Remote sensing modelling was found to better capture river mouth relative strength, and accumulation patterns were found consistent with hydrodynamic modelling. This methodology lays groundwork for developing an operational monitoring system to assess microplastic pollution emitted by a major river.
Highlights
Marine plastic litter has long been recognized as an environmental problem (Azzarello and van Vleet, 1987; Law and Thompson, 2014; Sheavly and Register, 2007) but only recently has begun to receive international attention at a level adequate to the potential severity of the threat (G7 Germany, 2015; GESAMP, 2016; UNEP, 2016)
ChlA measurements fell within 0.005–0.043 mg/L, and suspended particulate matter (SPM) values covered a moderate range as compared with ARPA ER monitoring measurements of SPM from Pontelagoscuro
Water microplastic samples analyzed by Attenuated Total Reflectance (ATR) Fourier Transform Infrared (FT-IR) and shortwave infrared (SWIR) spectroscopy ranged from 1 to 84 particles/m3 (Fig. 2), with the highest concentrations being found along the outer river plume edge, within the main arm of the river (Po della Pila) and the side channel Busa di Tramontana
Summary
Marine plastic litter has long been recognized as an environmental problem (Azzarello and van Vleet, 1987; Law and Thompson, 2014; Sheavly and Register, 2007) but only recently has begun to receive international attention at a level adequate to the potential severity of the threat (G7 Germany, 2015; GESAMP, 2016; UNEP, 2016). Microplastics, commonly defined as particles < 5 mm in diameter (Galgani et al, 2013), are increasingly proving to be ubiquitous in all water systems. Despite the fact that freshwater systems are at least as severely contaminated as the oceans (Dris et al, 2015), large rivers have to date received relatively little attention (Mani et al, 2015; Wagner et al, 2014). An estimated 1.15 and 2.41 million tonnes enter the oceans each year from rivers alone (Lebreton et al, 2017), representing up to 50% of land based plastic emissions estimate, which ranges from 4.8 to 12.7 million tonnes (Jambeck et al, 2015). Once microplastics reach coastal waters, their dispersion and transportation pathways are governed by ocean and atmosphere dynamics; our understanding of these physical processes is still limited. Some authors suggest that how these processes influence microplastic transport may, to some extent, be comparable to well-studied suspended sediment transportation systems (Zhang, 2017), which could offer a more established framework for modelling suspended microplastic transportation
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
