Downward migrating microplastic in lake sediments is a tricky indicator for the onset of the Anthropocene

Abstract

Plastics are a particulate novel material in Earth’s history. Due to its persistence and wide-range presence, it has a great potential of being a global age marker and correlation tool between sedimentary profiles. Hence, microplastics are currently considered among the array of proxies to delimit the Anthropocene Epoch (starting from year 1950 and above). Here we present a study of microplastics deposition history inferred from sediment profiles of three lakes in north-eastern Europe. The sediments were dated with independent proxies from nowadays back to the first half of the 18th century. Surprisingly, regardless of the sediment layer age, we found microplastic particles throughout the cores in all sites. The factor driving microplastic particles to penetrate deeper in sediment layers appears to be particles' dimensional (aspect) ratio: less elongated particles tend to be transported deeper while more elongated particles and fibres have a decreased ability to be mobile. We conclude that interpretation of microplastics distribution in sediment profiles is ambiguous and does not strictly indicate the beginning of the Anthropocene Epoch.