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.