When monitoring microplastic (MP) and tire wear particles (TWP) in marine sediments, the sample analysed is meant to be representative. However, is only a single grab enough to represent their concentration on the seabed? In this study, we assess the MP and TWP distribution variability on the seabed by sampling two grids of approx. 1 km² located in Danish waters. We collected respectively 13 and 16 samples. The aim was to understand how many samples are needed to represent the mean concentration and the uncertainty compared to collecting a single grab. To extract MPs and TWPs from the sediments, samples underwent pre-oxidation, density separation, incubation by surfactants followed by multiple enzymatic digestions, Fenton oxidation, and further density separation. Extracts were analysed by FPA-µFTIR imaging for the identification of MPs and Pyr-GC/MS for TWP. The first technique provides MPs counts and allows for mass estimation. The latter technique quantifies TWP-mass but not particles’ number. The preliminary results showed that the first grid had the MP concentration ranging from 250 and 24848 µg/kg dw, while TWP varied between 58 and 35197 µg/kg dw. Initial results indicate that the variability of the second grid is of similar order. This study indicates that a single grab sample does not represent the concentration over a small area like 1 km². However, multiple samples are needed to fully map the content of MP and TWP at the sampled location. This study contributes significantly to providing guidelines for sampling strategies within the MSFD and OSPAR guidelines.

Primary Presenter: Jeanette Lykkemark, Aalborg University (jly@build.aau.dk)

Authors:

Jeanette Lykkemark, Aalborg University  (jly@build.aau.dk)

Laura Sanchez, Aalborg University  ()

Fan Liu, Aalborg University  ()

Rupa Chand, Aalborg University  ()

Jes Vollertsen, Aalborg University  ()