Zinc

• The journey isn’t far either, as we’re by the city of Kuopio, which is surrounded by Finland’s 10th largest lake.
• We’re crossing the icy bay not for sport or holiday activities, nor is it part of a plan to hike to north Pole.
• Mud – or sediments, as geologists call them – are deposited slowly at the bottom of lakes.
• Lake Kallavesi has a specific and rare type of sediments called annually laminated or varved sediments.

The history of plastic, buried in the mud

• It’s a continuation of our ongoing research, most recently published in the Journal of Soils and Sediments in February 2023.
• Widespread use of plastic started about 70 years ago, and since then, 9 billion metric tonnes has been produced.
• It would be nice to work on lake on a sunny summer day, but the thick ice serves as a stable platform.
• We use metal rods to push the core tubes down 11 metres to the lake floor and then into the sediment.
• This benefit is also plastic’s worst aspect: released into the environment, it doesn’t decompose but breaks into ever smaller pieces.

The ABCs of reading sediment layers

• It might be the noise or maybe it is just excitement – after all, you never know beforehand what the sediment will look like.
• The thicker the bright layer is, the more intensive the spring flood and higher the snow was during the winter.
• Building a bridge or a road involves digging and can increase erosion, and our sediment shows bright layers that can be several centimetres thick.
• Today, however, I’m planning my playing in more detail, having spent weeks in the laboratory preparing these sediments for analysis.

Two steps forward, one steps back

• Unfortunately, that’s not the case for microplastics – their presence in the sediments is increasing over time.
• The materials most frequently found are polyethylene, polypropylene and polystyrene, often employed for so-called single-use products such as packaging.
• To learn more, visit the site of the Axa Research Fund or follow on Twitter @AXAResearchFund.