5. CONCLUSIONS
In our study of the dissolved inorganic chemistry in the lower Kolyma basin, we found that the ionic HCO3-Ca-Mg water type was prevalent (representing both lakes and permafrost ice), and the river and permafrost creek waters had also a significant admixture of sulphate. The highest concentrations of DOC (9.13-127 mg/L) were found in permafrost ice, permafrost creeks and thermokarst lakes, i.e. the water bodies connected to permafrost thaw. Among the collected water samples, a few heavy metals were detected at higher concentrations in permafrost-related samples than elsewhere, i.e. As, Cd, Co, Fe, Mn, Ni, and V. The occasionally detected Cr, Hg, Pb and Ti were also typically associated with the permafrost-related origin of a sample. Mercury occurred also at a relatively high concentration in the Maly Anyui tributary of Kolyma. The highest concentrations of most of the studied elements were found in the lake bottom waters, suggesting that thermokarst lakes act as local traps for elements, including heavy metals. Further evidence for the origin of these metals could be provided in the future through sampling lake bottom sediments as well.
The impact of changes in permafrost regions, occurring due to climate change, need to be considered with respect to both the remobilisation from older permafrost (of organic carbon and other chemical components) and the interference with newly deposited anthropogenic contaminants. Such impacts are likely to be complex and modified by the local sedimentation processes in the local watercourses and lakes. The further forecasted climate change may result in the formation of new flow pathways for dissolved chemicals migrating between supra-, intra- and subpermafrost waters. Further research into the concentration of dissolved and particulate phases in permafrost thaw and active layer waters is warranted to diminish the uncertainties related to this field of knowledge or to estimate the total load of e.g. heavy metals in the permafrost regions, available to remobilisation.