Greenland in the Anthropocene: an archive of microplastic pollution

Glacimarine sediment results from glaciers weathering the rock exporting silt and clay into the ocean. Such fine sediments are also exported from the Greenlandic Ice Sheet where new sources of plastic pollution like seasonal ice thawing may be releasing microplastics (MP) back to the environment. MP could be then transported to the seafloor via sediment burial and incorporated into the layers of the geological record. However, the purification and extraction of MP from such a fine-grain matrix is challenging, as the small grains remain in suspension and can form aggregates. In order to look for a footprint of the Anthropocene in Greenland, a sediment core was analyzed to generate a record of MP by comparing a pre- and post-plastic boom period. Using ²¹⁰Pb and ¹³⁷Cs dating, the chronology was established from 1861 to 2015 ±5 yrs bridging the plastic boom of the 1950s. Using a 4-step methodology developed for fine-grain matrices, MP particles were characterized via FT-IR imaging. QC/QA protocols were applied throughout the process to reduce the risk of contamination. More than 1000 particles were found in total ranging from 20 µm to 600 µm and going as far back as 1930. Nine polymer types were found, the most common being PE and PP accounting for 84% of all particles. This is the first sediment record of MP pollution in the Arctic, which shows that once thought pristine regions have in fact being polluted for a long time, which in turn implies that the impact might be greater than previously thought. In addition, this long-term accumulation in Greenlandic marine sediment could be compared to global horizons in the search for markers of the Anthropocene.