Polymer type affects the vertical distribution of microplastics in boreal lake sediments

Abstract

Lakes are disproportionately affected by microplastic pollution, and an estimated 99% of microplastics eventually settle in bottom sediments. Yet, knowledge on the mechanisms driving microplastic accumulation in lake sediments is limited. This thesis provides a literature review and contributes to a whole-ecosystem experiment called The pELAstic Project to elucidate the fate of microplastics in lake ecosystems. Three common microplastic polymers of different densities and sizes were added to Lake 378 at the IISD – Experimental Lakes Area. Sediment cores and sediment grab samples were collected across a water depth gradient. Sediment characteristics differed significantly between littoral and profundal samples. A negative association was found for water depth and one of the polymers; sediment depth was a helpful predictor of microplastic concentration across polymers. An interaction between sediment depth and size fraction was identified. This work contributes to microplastic hotspot prediction in sediment to direct the development of in situ remediation methods.