Proglacial river sediments are a substantial sink of perfluoroalkyl substances released by glacial meltwater

Abstract

How climate change will influence the accumulation of pollutants in remote mountainous lakes is poorly understood. Here we collected sediment cores from two glacial lakes (one is small and close to glacier, and the other is large and far from glacier) in the Third Pole and quantified deposition fluxes of perfluoroalkyl substances. The trends of perfluoroalkyl substances fluxes broadly correspond with their historical emissions and phase-out. Besides of emission, glacial meltwater strongly impacts the accumulation of perfluoroalkyl substances in the small lake, while precipitation exhibits great impact on that of the big lake. We then modified the Quantitative Water Air Sediment Interaction model to explore how perfluoroalkyl substances transport along proglacial rivers before entering the big lake and found that river sediments intercept ~13% of perfluoroalkyl substances from glacial meltwater. With climate warming and increased glacial meltwater, proglacial river sediments will play an important role in retaining perfluoroalkyl substances.