Mercury in Deep Ice-Rich Permafrost Deposits of Siberia

• Main Author: Rutkowski, Clara
• Format: Thesis
• Language: unknown
• Published: 2019
• Subjects: Arctic Ocean; Ice; laptev; Laptev Sea; Magnetic susceptibility; permafrost; Yakutia; Siberia
• Online Access: https://epic.awi.de/id/eprint/52090/; https://hdl.handle.net/10013/epic.53cfb0a0-233e-45ab-900d-17fe347603d1

The ice-rich permafrost in Siberia (`Yedoma´) is extraordinarily prone to thawing due to Arctic warming resulting in an increased sediment input from coastal shorelines and river floodplains to the Laptev Sea. Freeze-locked deposits including hazardous heavy metals are now entering the Arctic Ocean. Shallow Arctic soil layers often show high levels of mercury (Hg). In this study, Hg concentrations from various deposits in Siberia´s deep permafrost soil were determined. Links between sediment properties and the Hg enrichment in order to assess a first deep Hg inventory in Pleistocene permafrost down to 36 m below surface were explored as well. Sediment profiles from seven sites of different permafrost degradation states on Bykovsky Peninsula (Northern Yakutia) and in the Yukechi Alas region (Central Yakutia) were analyzed for Hg content using a Direct Mercury Analyzer (DMA-80), based on photometric absorption. Total carbon, total nitrogen and organic carbon as well as grain size distribution, bulk density and mass specific magnetic susceptibility were investigated as sediment property parameters. Results reveal a Hg concentration of 9.72 ± 9.28 μg kg-1 and an explicit correlation of Hg to organic carbon, total nitrogen, grain size distribution and mass specific magnetic susceptibility. Moreover, Hg concentrations are higher in the generally sandier sediment of the Bykovsky Peninsula than in the siltier sediment of the Yukechi Alas. This is counterintuitive and may well be explained by proximity to the ocean and higher clay content in the more poorly sorted grain sizes there. This case study showed that the deep permafrost sediments, frozen since millennia, verifiably contain Hg. Even though it might not be an alarming amount, it could re-enter the recent biogeochemical cycles after thaw with ongoing Arctic warming.