1. INTRODUCTION
Permafrost loss has been observed widely in the Northern Hemisphere
since the second half of 20th century (Streletskiyet al. , 2015) and it has impacted markedly both terrestrial and
aquatic environments (Mann et al. , 2022; Vonk et al. ,
2015). Further significant changes are predicted in permafrost
environments during the 21st century (Smith et
al. , 2022; Streletskiy et al. , 2021; Teufel & Sushama, 2019) as
the climate warms (Overland J., 2017; Overland et al. , 2014).
Such changes will be both vertical and horizontal, resulting in deeper
active layers (Abramov et al. , 2021), shrinking permafrost
extent, and the retreat of its respective zones (Lim et al. ,
2019; Streletskiy, 2021). The progressing permafrost degradation leads
to important and lasting changes in geomorphological processes (Rudyet al. , 2017; Tananaev & Lotsari, 2022), hydrological phenomena
(Rudy et al. , 2017; Suzuki et al. , 2021) and
biogeochemical cycles (Grosse et al. , 2016; Mann et al. ,
2012; Vonk et al. , 2015).
Hydrochemical changes in permafrost regions are increasingly probable,
leading to both temporary and permanent hazards to the surface water
quality in the Arctic (Brubaker et al. , 2012; Gunnarsdóttiret al. , 2019). Permafrost active layer deepening and the
formation of new thermokarst lakes, taliks and drainage pathways
(Dzhamalov & Safronova, 2018; in’t Zandt et al. , 2020; Tananaev
& Lotsari, 2022) all lead to changes in the migration of chemical
compounds (Frey & Mcclelland, 2009; Monhonval et al. , 2021) both
horizontally and vertically (Ji et al. , 2021; Tananaev et
al. , 2021). The newly formed drainage pathways may leach chemical
compounds from layers previously disconnected from groundwater flow (Jiet al. , 2021; Lim et al. , 2019). Thermoerosion phenomena
lead to intense erosion and thaw slump formation. Such phenomena impact
the fluvial transport of suspended sediment and chemical compounds along
the main hydrological pathways, to the estuaries and the ocean (Chalovet al. , 2018; Frey & Mcclelland, 2009; Kokelj et al. ,
2013; Toohey et al. , 2016). Both natural and antropogenic
chemical compounds may become mobilised from permafrost into surface
waters (Kosek et al. , 2019; Lehmann-Konera et al. , 2018),
and the anthropogenic compounds may be of both local and
long-range-transport origin (Potapowicz et al. , 2019; Szopińskaet al. , 2016).
The studies on the hydrochemical impacts of climate change in Siberian
Arctic rivers have focused mainly on the organic carbon (OC) transport,
including the dissolved OC (DOC), suspended particulate OC (POC) and
riverbed sediment OC (SOC) (e.g., Holmes et al. , 2012; Jonget al. , 2022; Mann et al. , 2012; Wild et al. ,
2019). Compared to the research on OC, the recognition of inorganic
elements transport, including heavy metals, is relatively poor and
limited to selected elements (Ji et al. , 2021; Kuchmenko et
al. , 2002; Lim et al. , 2019). Systematic research on the
potential accumulation of heavy metals in permafrost has only been
conducted on mercury (Wang et al. , 2022). Therefore, we present a
study on the possible release of contaminants from permafrost into
freshwater. Our objective was to perform a detailed hydrochemical
assessment of permafrost thaw impact on the inorganic chemicals
occurrence in the lower Kolyma River basin. We investigate this question
in various freshwater environments: thermokarst lakes, permafrost ice,
permafrost thaw creeks, and in watercourses representing various
proportions of permafrost thaw supply.