What is hiding below the surface - MPs including TWP in an urban lake

Marziye Shabnam Molazadeh; Fan Liu; Jeanette Lykkemark; Lucian Lordachescu; Asbjørn Haaning Nielsen; Jes Vollertsen

doi:10.1016/j.envint.2023.108282

What is hiding below the surface - MPs including TWP in an urban lake

Environ Int. 2023 Dec:182:108282. doi: 10.1016/j.envint.2023.108282. Epub 2023 Oct 31.

Authors

Marziye Shabnam Molazadeh¹, Fan Liu², Jeanette Lykkemark², Lucian Lordachescu², Asbjørn Haaning Nielsen², Jes Vollertsen²

Affiliations

¹ Aalborg University, Section of Civil and Environmental Engineering, Department of the Built Environment, Thomas Manns Vej 23, 9220 Aalborg Øst, Denmark. Electronic address: marziyem@build.aau.dk.
² Aalborg University, Section of Civil and Environmental Engineering, Department of the Built Environment, Thomas Manns Vej 23, 9220 Aalborg Øst, Denmark.

PMID: 37952413
DOI: 10.1016/j.envint.2023.108282

Abstract

Inland lakes play an important role as habitats for local species and are often essential drinking water reservoirs. However, there is limited information about the presence of microplastics (MPs) in these water bodies. Thirteen sediment samples were collected across a Danish urban lake to map MPs, including tyre wear particles (TWP). The lower size detection limit was 10 µm. MPs were quantified as counts, size, and polymer type by Fourier-transform infrared microspectroscopy (µFTIR) and mass estimated from the 2D projections of the MPs. As TWP cannot be determined by µFTIR, counts and sizes could not be quantified by this technique. Instead, TWP mass was determined by pyrolysis gas chromatography mass spectrometry (Py-GC/MS). The average MP abundance was 279 mg kg^-1 (µFTIR), of which 19 mg kg^-1 (Py-GC/MS) were TWP. For MPs other than tyre wear, the average MP count concentration was 11,312 counts kg^-1. Urban runoff from combined sewer overflows and separate stormwater outlets combined with outflow from a wastewater treatment plant were potential point sources. The spatial variation was substantial, with concentrations varying several orders of magnitude. There was no pattern in concentration across the lake, and the distribution of high and low values seemed random. This indicates that large sampling campaigns encompassing the entire lake are key to an accurate quantification. No preferential spatial trend in polymer characteristics was identified. For MPs other than TWP, the size of buoyant and non-buoyant polymers showed no significant difference across the lake, suggesting that the same processes brought them to the sediment, regardless of their density. Moreover, MP abundance was not correlated to sediment properties, further indicating a random occurrence of MPs in the lake sediments. These findings shed light on the occurrence and distribution of MPs, including TWP, in an inland lake, improving the basis for making mitigation decisions.

Keywords: Microplastics; Py-GC/MS; Sediments; Tyre wear particles; Urban Lake; µFTIR.

MeSH terms

Environmental Monitoring / methods
Geologic Sediments / chemistry
Lakes / chemistry
Microplastics* / analysis
Plastics / chemistry
Water Pollutants, Chemical* / analysis

Substances

Microplastics
Plastics
Water Pollutants, Chemical