Permafrost coverage, watershed area and season control of dissolved carbon and major elements in western Siberian rivers

Abstract

Abstract. Analysis of organic and inorganic carbon (DOC and DIC, respectively), pH, Na, K, Ca, Mg, Cl, SO4 and Si in ~ 100 large and small rivers (< 10 to ≤ 150 000 km2) of western Siberia sampled in winter, spring, and summer over a more than 1500 km latitudinal gradient allowed establishing main environmental factors controlling the transport of river dissolved components in this environmentally important region, comprising continuous, discontinuous, sporadic and permafrost-free zones. There was a significant latitudinal trend consisting in a general decrease in DOC, DIC, SO4, and major cation (Ca, Mg, Na, K) concentration northward, reflecting the interplay between groundwater feeding (detectable mostly in the permafrost-free zone, south of 60° N) and surface flux (in the permafrost-bearing zone). The northward decrease in concentration of inorganic components was strongly pronounced both in winter and spring, whereas for DOC, the trend of concentration decrease with latitude was absent in winter, and less pronounced in spring flood than in summer baseflow. The most significant decrease in K concentration from the southern (< 59° N) to the northern (61–67° N) watersheds occurs in spring, during intense plant litter leaching. The latitudinal trends persisted for all river watershed size, from < 100 to > 10 000 km2. Environmental factors are ranked by their increasing effect on DOC, DIC, δ13CDIC, and major elements in western Siberian rivers as follows: watershed area < season < latitude. Because the degree of the groundwater feeding is different between large and small rivers, we hypothesize that, in addition to groundwater feeding of the river, there was a significant role of surface and shallow subsurface flow linked to plant litter degradation and peat leaching. We suggest that plant-litter- and topsoil-derived DOC adsorbs on clay mineral horizons in the southern, permafrost-free and discontinuous/sporadic permafrost zone but lacks the interaction with minerals in the continuous permafrost zone. It can be anticipated that, under climate warming in western Siberia, the maximal change will occur in small (< 1000 km2 watershed) rivers DOC, DIC and ionic composition and this change will be mostly pronounced in summer.

Size Distribution, Surface Coverage, Water, Carbon, and Metal Storage of Thermokarst Lakes in the Permafrost Zone of the Western Siberia Lowland

“…The filtered samples were stored at 4-5 • C in the dark, before analysis. The concentrations of dissolved organic and inorganic carbon (DOC and DIC, respectively), cations, and trace elements (TEs), were measured using routine methods for analyzing boreal water samples in the GET laboratory (Toulouse) [79,80]. The DOC and DIC were measured using a Shimadzu Total Organic Carbon Analyzer TOC 6000 with an uncertainty of 5%.…”

“…The stock of dissolved components in lakes on the permafrost-affected WSL territory can be compared to that delivered by all rivers of the WSL from the same territory to the Arctic Ocean. For this, watershed size-averaged, year-round fluxes of carbon, and major and trace elements assessed in previous works [79,80], can be used. A diagram of element stock in thermokarst lakes, relative to that in rivers of the WSL, is presented in Figure 6.…”

“…Three groups of elements can be distinguished: (i) major and trace elements, whose storage in lakes is less than 10% of that in rivers (DIC, Mg, Ca, Sr, Ba, K, Si, B, Fe, Co, Ni, Mn, and Ce); (ii) elements presenting non-negligible storage in lakes (20% ± 10% of that in rivers): DOC, Rb, Zn, Cu, V, Mo, Zr, As, Nd, and Th; and finally (iii) elements having significant, 30 to 70% storage in lakes, relative to rivers: Cd, Pb, La, Cr, and Al. It can be seen from this classification that major cations, DIC, B, Si, and metals subjected to significant redox transformations (Mn, Fe, and Ce), are essentially present in the rivers because they are delivered by groundwater feeding or shallow subsurface flux [79,80]. The groundwater and subsoil feeding are very low in lakes which have frozen peat on the border and frozen sediments at the bottom, throughout the year [54].…”

Towards the Marine Arctic Component of the Pan-Eurasian Experiment

“…Due to mentioned scarcity in hydrological monitoring, the main datasets are based on regional studies recently performed in Lena (Hölemann et al 2005), Ob (Shakhova et al 2007), and Amur (Levshina 2008 Chudaeva et al 2011) rivers, and summarised in reviews (Savenko 2006;Bagard et al 2011;Pokrovsky et al 2015). Some of the large rivers (e.g.…”

Dissolved organic carbon and major and trace elements in peat porewater of sporadic, discontinuous, and continuous permafrost zones of western Siberia

“…The specific UV absorbency (SUVA 280 , L mg −1 m −1 ) is used as a proxy for aromatic C, molecular weight, and source of dissolved organic matter (DOM) (Uyguner and Bekbolet, 2005;Weishaar et al, 2003;Ilina et al, 2014, and references therein). The SUVA 280 in the present study was used for consistency with previous measurements of lakes and rivers in western Siberia (Shirokova et al, 2013;Manasypov et al, 2015Manasypov et al, , 2017Pokrovsky et al, 2015) and permafrost-draining rivers in central Siberia .…”