Hotspots of microplastic accumulation at the land-sea transition and their spatial heterogeneity: The Po River prodelta (Adriatic Sea)

C Pellegrini; F Saliu; A Bosman; I Sammartino; C Raguso; A Mercorella; D S Galvez; A Petrizzo; F Madricardo; M Lasagni; M Clemenza; F Trincardi; M Rovere

doi:10.1016/j.scitotenv.2023.164908

Hotspots of microplastic accumulation at the land-sea transition and their spatial heterogeneity: The Po River prodelta (Adriatic Sea)

Sci Total Environ. 2023 Oct 15:895:164908. doi: 10.1016/j.scitotenv.2023.164908. Epub 2023 Jun 27.

Authors

C Pellegrini¹, F Saliu², A Bosman³, I Sammartino⁴, C Raguso², A Mercorella⁴, D S Galvez⁴, A Petrizzo⁴, F Madricardo⁴, M Lasagni², M Clemenza⁵, F Trincardi⁶, M Rovere⁴

Affiliations

¹ Consiglio Nazionale delle Ricerche (CNR), Istituto di Scienze Marine (ISMAR-CNR), Italy. Electronic address: claudio.pellegrini@bo.ismar.cnr.it.
² Earth and Environmental Science Department, University of Milano Bicocca, Milano, Italy.
³ Consiglio Nazionale delle Ricerche (CNR), Istituto di Geologia Ambientale e Geoingegneria (IGAG), Italy.
⁴ Consiglio Nazionale delle Ricerche (CNR), Istituto di Scienze Marine (ISMAR-CNR), Italy.
⁵ INFN Sezione di Milano-Bicocca, Piazza della Scienza 3, 20126 Milano, Italy.
⁶ Consiglio Nazionale delle Ricerche (CNR), Dipartimento di Scienze del Sistema Terra e Tecnologie per l'Ambiente (DSSTTA), Rome, Italy.

PMID: 37385497
DOI: 10.1016/j.scitotenv.2023.164908

Abstract

Deltas are the locus of river-borne sediment accumulation, however, their role in sequestering plastic pollutants is still overlooked. By combining geomorphological, sedimentological, and geochemical analyses, which include time-lapse multibeam bathymetry, sediment provenance, and μFT-IR analyses, we investigate the fate of plastic particles after a river flood event providing an unprecedented documentation of the spatial distribution of sediment as well as of microplastics (MPs), including particles fibers, and phthalates (PAEs) abundances in the subaqueous delta. Overall sediments are characterized by an average of 139.7 ± 80 MPs/kg d.w., but display spatial heterogeneity of sediment and MPs accumulation: MPs are absent within the active sandy delta lobe, reflecting dilution by clastic sediment (ca. 1.3 Mm³) and sediment bypass. The highest MP concentration (625 MPs/kg d.w.) occurs in the distal reaches of the active lobe where flow energy dissipates. In addition to MPs, cellulosic fibers are relevant (of up to 3800 fibers/kg d.w.) in all the analyzed sediment samples, and dominate (94 %) with respect to synthetic polymers. Statistically significant differences in the relative concentration of fiber fragments ≤0.5 mm in size were highlighted between the active delta lobe and the migrating bedforms in the prodelta. Fibers were found to slightly follow a power law size distribution coherent with a one-dimensional fragmentation model and thus indicating the absence of a size dependent selection mechanism during burial. Multivariate statistical analysis suggests traveling distance and bottom-transport regime as the most relevant factors controlling particle distribution. Our findings suggest that subaqueous prodelta should be considered hot spots for the accumulation of MPs and associated pollutants, albeit the strong lateral heterogeneity in their abundances reflects changes in the relative influence of fluvial and marine processes.

Keywords: Hot spots; Impact on marine food-chain; Microplastics; Phthalates; River delta; Sedimentary processes.