Abstract
Abstract. In order to better understand the chemical composition of snow and its impact on surface water hydrochemistry in the poorly studied Western Siberia Lowland (WSL), the surface layer of snow was sampled in February 2014 across a 1700 km latitudinal gradient (ca. 56.5 to 68° N). We aimed at assessing the latitudinal effect on both dissolved and particulate forms of elements in snow and quantifying the impact of atmospheric input to element storage and export fluxes in inland waters of the WSL. The concentration of dissolved+colloidal (< 0.45 µm) Fe, Co, Cu, As and La increased by a factor of 2 to 5 north of 63° N compared to southern regions. The pH and dissolved Ca, Mg, Sr, Mo and U in snow water increased with the rise in concentrations of particulate fraction (PF). Principal component analyses of major and trace element concentrations in both dissolved and particulate fractions revealed two factors not linked to the latitude. A hierarchical cluster analysis yielded several groups of elements that originated from alumino-silicate mineral matrix, carbonate minerals and marine aerosols or belonging to volatile atmospheric heavy metals, labile elements from weatherable minerals and nutrients. The main sources of mineral components in PF are desert and semi-desert regions of central Asia. The snow water concentrations of DIC, Cl, SO4, Mg, Ca, Cr, Co, Ni, Cu, Mo, Cd, Sb, Cs, W, Pb and U exceeded or were comparable with springtime concentrations in thermokarst lakes of the permafrost-affected WSL zone. The springtime river fluxes of DIC, Cl, SO4, Na, Mg, Ca, Rb, Cs, metals (Cr, Co, Ni, Cu, Zn, Cd, Pb), metalloids (As, Sb), Mo and U in the discontinuous to continuous permafrost zone (64–68° N) can be explained solely by melting of accumulated snow. The impact of snow deposition on riverine fluxes of elements strongly increased northward, in discontinuous and continuous permafrost zones of frozen peat bogs. This was consistent with the decrease in the impact of rock lithology on river chemical composition in the permafrost zone of the WSL, relative to the permafrost-free regions. Therefore, the present study demonstrates significant and previously underestimated atmospheric input of many major and trace elements to their riverine fluxes during spring floods. A broader impact of this result is that current estimations of river water fluxes response to climate warming in high latitudes may be unwarranted without detailed analysis of winter precipitation.
Highlights
To identify the group of elements that behaved in a similar way in snow water and snow particles, we applied a complementary hierarchical cluster analysis (HCA; Hartigan, 1975; Kaufman and Rousseeuw, 2005), which is widely adopted in geochemical interpretations of element concentration data (e.g., Bini et al, 2011; Levitan et al, 2015; Schot and van der Wal, 1992; Moragues-Quiroga et al, 2017)
Zn and Pb did not exhibit any systematic effect of latitude, and Sb, Cd and Ni exhibited a single maximum at ca. 63–65◦ N
The chemical composition of surface layer of snow cover was studied across a 1700 km latitudinal gradient in the Western Siberia Lowland (WSL)
Summary
The snow cover exhibits a number of properties making it a unique natural archive and indicator of the ecosystem status (Baltrenaiteet al., 2014; Bokhorst et al, 2016; Callaghan et al, 2011; de Caritat et al, 1998, 2005; Garbarino et al, 2002; Guéguen et al, 2016; Kashulina et al, 2014; Lisitzin, 2002; Niu et al, 2016; Ross and Granat, 1986; Singh et al, 2011; Siudek et al, 2015; Van de Velde et al, 1999; Walker et al, 2003). The dissolved (< 0.45 μm or < 0.22 μm) fraction of snow was traditionally studied in European subarctic (de Caritat et al, 1998; Chekushin et al, 1998; Kashulina et al, 2014; Reimann et al, 1991, 2000; Reinosdotter and Viklander, 2005) but the data on trace elements in snow water collected in boreal, Arctic and subarctic regions are limited This is especially true for large and geographically homogeneous territories of western Siberia, presenting relatively similar levels of snow deposition during winter seasons (i.e., from 100 mm of water in the south to 140–150 mm of water in the north) without any pronounced influence of large industrial centers, mountain regions and marine aerosols over the territory close to 1.5 million km (Resources of Surface Waters of USSR, 1972, 1973; Boyarkina et al, 1993)
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