763 ISSN 1028-334X, Doklady Earth Sciences, 2018, Vol. 480, Part 2, pp. 763–766. © Pleiades Publishing, Ltd., 2018. Original Russian Text © A.S. Prokushkin, O.S. Pokrovsky, M.A. Korets, A.V. Rubtsov, S.V. Titov, I.V. Tokareva, R.A. Kolosov, R.M.W. Amon, 2018, published in Doklady Akademii Nauk, 2018, Vol. 480, No. 4, pp. 480–484. Sources of Dissolved Organic Carbon in Rivers of the Yenisei River Basin A. S. Prokushkin a,b, *, O. S. Pokrovsky c , M. A. Korets a , A. V. Rubtsov a,b , S. V. Titov a , I. V. Tokareva a , R. A. Kolosov a , and R. M. W. Amon d Presented by Academician E.A. Vaganov September 23, 2015 Received September 23, 2015 Abstract—The spatial and temporal variations in concentrations of dissolved organic carbon in the Yenisei River and its major tributaries are analyzed. The results obtained suggest that the maximal contribution to the flows of dissolved organic carbon in the Yenisei River is made by cryohydromorphic forest landscapes of the Central Siberian Plateau. DOI: 10.1134/S1028334X18060077 Studies of the major rivers of the Arctic basin over the last two decades have allowed researchers to spec- ify the characteristics of carbon transport into the Arc- tic Ocean [1–6]. However, the absolute majority of these works are based on sampling at river outlets immediately before discharge into the terminal water object. This point complicates the identification of terrigenous carbon sources within particular land- scapes drained by a river network and, therefore, pre- diction of the response of hydrochemical carbon dis- charge into the Arctic Ocean under climate change. Thus, along with stationary long-term studies at river outlets, there is a great necessity to determine the quantitative and qualitative characteristics of carbon in rivers, the discharge of which is formed in basins with relatively homogeneous conditions in terms of climate, geological structure, soils, and vegetation [6–9]. In the present work, on the basis of analysis of tem- poral and spatial variability in the concentrations of dissolved organic carbon (DOC) in water of the Yeni- sei River and its main tributaries, we have attempted to identify the landscapes contributing to DOC dis- charge of the Yenisei River. The studies are based on generalization of the data on the carbon composition in water from the Yenisei River obtained by us in 2012–2015 and taken from the Arctic Great Rivers Observatory database (Arctic-GRO, http://arcticgre- atrivers.org/data.php [2]) for the period of 2003– 2015. To analyze the spatial variability in DOC con- centrations in the Yenisei River basin, 25 streams draining the western (n = 10) and eastern (n = 15) parts of the basin were selected; in June 2012 and May and August 2015, sampling of surface discharge was performed at these points. At the outlet of the Yenisei River (Igarka, 69° N, 88° E), the DOC concentrations in the period from 2003 to 2015 varied in a broad range (from 2.2 to 15.0 mg C/L) and were characterized by a power dependence on the water discharge: [DOC] = 0.061Q 0.47 , R 2 = 0.60, where [DOC] is the concentration in mg C/L and Q is the water discharge in m 3 /s. The peak values of DOC concentrations in the Yenisei River are usually observed in the period of spring thawing (≤15 mg C/L), indicating the predom- inant supply of solutions from organic soil horizons. In the summer–autumn period, the DOC concentra- tions decrease as a result of deeper infiltration of solu- tions into the soil and hence adsorption and microbi- ological transformations/mineralization of organic carbon in land ecosystems [8]. The average carbon export in the form of DOC from the Yenisei River basin was 5.37 ± 0.92 Tg C/yr, varying from 3.43 Tg C/yr in 2012 to 6.37 Tg C/yr in 2007; this parameter depends closely on the annual water discharge (Fig. 1a). The values of DOC dis- charge obtained by us agree with the variation ranges GEOGRAPHY a Sukachev Institute of Forestry, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk, 660036 Russia b Siberian Federal University, Krasnoyarsk, 660041 Russia c Géosciences Environment Toulouse, Centre national de la recherché scientifique, Toulouse, 31400 France d Texas Agriculture and Mechanical University at Galveston, Galveston, Texas, 77553 United States *e-mail: prokushkin@ksc.krasn.ru