—Bottom sediment cores from the Langtibeito (Yamal Peninsula) and Gol’tsovoe (Gydan Peninsula) background arctic lakes are studied. The sedimentation rate estimated from ²¹⁰Pb and ¹³⁷Cs accounted for 0.17 and 0.20 cm/y, respectively. The element composition, grain-size composition, and loss on ignition were determined layer-by-layer in both cores. The element concentrations in the bottom sediments of both lakes throughout the entire core length are at the background level. The mercury content in the subsurface layers of sediments in both lakes, unlike other elements, was much higher than its local background contents. This is likely related to its atmospheric influx through transboundary transport. The comparison of diatom and grain-size data revealed the rebuilding of lake ecosystems in response to lake shoaling. The bioindication methods are promising for reconstructing the recent climatic changes in arctic regions.

The paper presents data on the features of Hg distribution and its input in dated bottom sediments in two Arctic lakes: Longtibeito on the Yamal Peninsula and Gol’tsovoe on the Gydan Peninsula. The Hg concentrations are much higher in the upper layers of the sediments, and the enrichment factors are 14 and 10 at background concentrations of 4.3 and 5.2 ng g^–1, respectively. The sedimentation rates in both lakes are fairly high: the rate for Longtibeito Lake varied relatively little and is 660 ± 75 g m^–2 year^–1 on average, and that for Gol’tsovoe Lake decreased toward upper layers from 791 to 513 g m^–2 year^–1. The fluxes of total Hg in these lakes are principally different, but their lithogenic fluxes are approximately equal: 5–7 μg m^–2 year^–1. Mercury flux into Longtibeito Lake is much higher than into Gol’tsovoe Lake and amounts to 41.5 μg m^–2 year^–1. Layer-by-layer grain-size analysis with determination of Hg in each fraction, highlights differences between the lakes. The total Hg concentration in a layer in Gol’tsovoe Lake is controlled by the fine fraction (0.2 mm) particles with high Hg concentrations. One of the likely reasons for the increase in Hg concentration in the upper layers may have been the development of oil and gas fields in this territory.