3.3. Metals, metalloids and non-metals
Elemental concentrations exhibited a large variability (Figure 5), with
maxima typically found in P1-P2 (Duvanny Yar) samples (Be, Co, Sb, Se,
Sr, V), in the lower layers of lake waters (As, Cd, Cu, Fe, Mn, Ni, Si,
Zn) or in single samples from Kolyma river (Ba, Li, Mo). Only Al showed
the highest concentration in permafrost ice (sample P3). Multiple heavy
metals showed much higher concentrations in permafrost creeks and ice
(As 1.24-4.23 µg L-1, Cu 1.82-11.4 µg
L-1, Co 0.57-3.99 µg L-1, Mn
122-1300 µg/L, µg L-1Ni 3.36-16.5 µg
L-1) than in Kolyma and its tributaries (As 0.22-0.81
µg L-1, Cu 0.70-5.72 µg L-1, Co
0.01-0.05 µg L-1, Mn 0.61-14.1 µg
L-1, Ni 0.2-1.87 µg L-1(Suppl. Mat. 2 ). Permafrost samples also contained metals that
were not typically found in other samples: Ti (15.7-30.3 µg
L-1) and Hg (0.128-0.131 µg L-1). In
the lakes, several metals concentrations increased with water depth: Fe,
Mn, Ni and Zn concentrations did so in both lakes; Al, K, Sr in Lake 1,
and Cu, Pb, Sb in Lake 2. The only instances of an opposite direction of
change were Mo, Na and Sb in Lake 1. The highest concentrations of
selected elements in this study were observed in lake bottom waters,
e.g. [Cu] = 1370 µg/L, [Mn] = 4610 µg/L, and [Zn] = 687
µg/L. Bottom lake waters, permafrost creeks and ice were also enriched
with phosphorus (up to 34.7 µg/L in Lake 2, up to 512 µg/L in creeks and
43.3 µg/L in ice) (Suppl. Mat. 2 ).
Enrichment factors (EF) of all the collected samples indicate
significant or higher enrichment in heavy metals (As, Cd, Co, Cu, Mn,
Ni, Pb and Zn). The highest EFs in the dataset were found in lake bottom
waters for As, Co, Cu, Mn, Ni, Pb and Zn (Suppl. Mat. 1, Table
S4 ). Noteworthy is also the extremely high enrichment of the permafrost
ice and creeks, as well as Maly Anyui (A2) sample in Hg. Furthermore,
the concentration level of Cd was higher in the collected samples
connected to permafrost than elsewhere: in permafrost creeks, permafrost
ice, lower layers of lake water and in a few samples from the Kolyma
river in the K3 cross section. In that particular cross section, the
enrichment in Cd was higher in the mid-stream (samples K31 and K32) than
in the river bottom waters (K31b, K32b), testifying to the limited
mixing of dissolved elements in the vertical profile of the river,
suggesting their local supply.