ICMGP 2022 – On-Demand / Poster Presentation

Abstract Information :

Organic soils in the Circumpolar North may store large amounts of total mercury (THg) that could be mobilized by permafrost thaw. The Hudson Bay Lowlands (HBL) is the World?s second largest northern peatland, supports North America?s lowest latitude continuous permafrost, and contains 81-150 mg/m2 of THg in the top 300 cm of the soil profile according to published estimates. These estimates are speculative as there has been little research completed on the spatial patterns of THg in the HBL, and the size of the THg pool has not been verified by field sampling and analyses. To better understand the implications of permafrost thaw in the HBL on Hg cycling, cores of full peat profiles (ranging from 45 to 300 cm deep) were collected across the HBL at 35 sites representing a range of environments such as bogs, fens, permafrost plateaus, and thermokarst fens. These cores were sectioned into 4 cm increments, and analysed for THg and other elements (C, N, Ca, K, P). Preliminary analyses show that the pool of THg at our study sites is 9.5 mg/m2, which is lower than published estimates. Mean THg concentrations in surface peat (top 50 cm) differs slightly between locations from continuous and discontinuous zones of permafrost (101.3 ng/g and 83.4 ng/g, respectively), where THg from the surface of permafrost plateaus in the continuous zone is considerably higher than any other environment (mean = 199.6 ng/g). However there are no statistically significant variations in mean THg concentrations along the entire profile between fens (56.1 ng/g), thermokarst fens (50.1 ng/g), bogs (43.9 ng/g) and plateaus (31.9 ng/g). These results advance our understanding on the spatial distribution of THg storage through this globally significant and rapidly changing permafrost wetland.