Exploration of occurrence and sources of microplastics (>10 μm) in Danish marine waters

Yuanli Liu; Claudia Lorenz; Alvise Vianello; Kristian Syberg; Asbjørn Haaning Nielsen; Torkel Gissel Nielsen; Jes Vollertsen

doi:10.1016/j.scitotenv.2022.161255

Exploration of occurrence and sources of microplastics (>10 μm) in Danish marine waters

Sci Total Environ. 2023 Mar 20:865:161255. doi: 10.1016/j.scitotenv.2022.161255. Epub 2022 Dec 31.

Authors

Yuanli Liu¹, Claudia Lorenz², Alvise Vianello², Kristian Syberg³, Asbjørn Haaning Nielsen², Torkel Gissel Nielsen⁴, Jes Vollertsen²

Affiliations

¹ Department of the Built Environment, Aalborg University, Thomas Manns Vej 23, 9220 Aalborg, Denmark. Electronic address: yuanlil@build.aau.dk.
² Department of the Built Environment, Aalborg University, Thomas Manns Vej 23, 9220 Aalborg, Denmark.
³ Department of Science and Environment, Roskilde University, Universitetsvej 1, DK-4000 Roskilde, Denmark.
⁴ National Institute of Aquatic Resources, Technical University of Denmark, Kemitorvet, Building 202, DK-2800 Kgs. Lyngby, Denmark.

PMID: 36596418
DOI: 10.1016/j.scitotenv.2022.161255

Abstract

Microplastics (MPs) were quantified in Danish marine waters of the Kattegat and the southernmost part of Skagerrak bordering to it. Kattegat is a waterbody between Denmark and Sweden that receives inflow from the Baltic Sea and direct urban runoff from the metropolitan area of Copenhagen and Malmö. MPs were measured in 14 continuous transects while steaming between monitoring stations. MP levels tended to be highest close to the Copenhagen-Malmö area, albeit this was more obvious from the abundance of particles rather than mass. The outcome of the measurements allowed a rough MP budget in the Danish Straits region, suggesting that urban waste- and stormwater discharges could not be neglected as potential MP source in these waters. The marine samples were collected by pumping and filtering water over 10 μm steel filters, hereby sampling a total of 19.3 m³. They were prepared and analyzed by FPA-μFTIR imaging, and the scans interpreted to yield MP size, shape, polymer type, and estimated mass. The average concentration was 103 ± 86 items m^-3, corresponding to 23.3 ± 28.3 μg m^-3 (17-286 items m^-3; 0.6-84.1 μg m^-3). Most MPs were smaller than 100 μm and fragments dominated the samples. The carbonyl index was assessed for polyolefins, showing that oxidation increased with decreasing MP size, but did not correlate with distance to urban areas. A rough budget of MP in the Danish Straits region suggested that MPs discharged from urban waste- and stormwaters were an import source of MPs.

Keywords: MP abundance; Mass concentration; Microplastic sources; Microplastics; μFTIR-imaging.