Рубрики:
COLLECTOR ICP-MS
DISSOLVED SILICON
ORGANIC-CARBON
TRACE-ELEMENTS
BOREAL RIVERS
NW RUSSIA
FLUXES
FRACTIONATION
WATERS
VARIABILITY
Кл.слова (ненормированные):
Silicon isotopes -- Fluxes -- Permafrost -- Siberia -- River -- Plants
COLLECTOR ICP-MS
DISSOLVED SILICON
ORGANIC-CARBON
TRACE-ELEMENTS
BOREAL RIVERS
NW RUSSIA
FLUXES
FRACTIONATION
WATERS
VARIABILITY
Кл.слова (ненормированные):
Silicon isotopes -- Fluxes -- Permafrost -- Siberia -- River -- Plants
Аннотация: This work is devoted to the characterization of natural mechanisms of silicon isotope fractionation within Siberian watersheds and predicting the climate warming effect on Si fluxes from the land to the Arctic Ocean. To unravel the different sources of silica generated by basalt weathering in Central Siberia under permafrost and larch deciduous forest conditions, we measured the Si isotopic composition of large and small rivers, surface flow, interstitial soil solutions, plant litter and soils. The average annual discharge-weighted delta Si-30 values of the second largest tributary of the Yenissei River, Nyzhnaya Tunguska and its main northern tributary (Kochechum) are equal to 1.08 +/- 0.10% and 1.67 +/- 0.15%, respectively, while their average annual Si concentrations are very similar (3.46 and 3.50 mg/L, respectively). During summer baseflow, the dissolved Si isotope composition of both large rivers and a small stream ranges between 1.5 and 2.5%. This is much heavier compared to the source basaltic rocks but similar to the fresh litter of Larix gmelinii, the dominating tree species in this region. It could be consistent with litter degradation in the uppermost soil horizons being the dominant source of solutes annually exported by Central Siberian rivers. During spring flood, accounting for 60-80% of annual Si flux, the delta Si-30 of the large rivers' dissolved load decreases by 1-1.5%, thus approaching the value of the bedrock and the silicate suspended matter of the rivers (RSM). This may reflect the dissolution of the silicate suspended load at high water/mineral ratio. The winter delta Si-30 values of the large river dissolved load range between 1.0 and 2.5%. During this period, contributing to <= 10% of the annual Si chemical flux, the interaction between bedrock (porous tuffs) and deep ground waters occurs at a very high solid/solution ratio, leading to the precipitation of isotopically light secondary minerals and enrichment of Si-30 in the fluids that feed the river through the unfrozen flowpaths. Results of this study imply that more than a half of the silica transported by Siberian rivers may transit through the biogenic pool and that, like in other stable basaltic regions, bedrock-water interactions account for a lesser fraction of the silica flux. As a result of projected future climate warming and weathering increases in boreal regions, the delta Si-30 isotopic composition of large Siberian rivers is likely to shift towards less positive values. (c) 2013 Elsevier B.V. All rights reserved.
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Полный текст,
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Держатели документа:
[Pokrovsky, O. S.
Schott, J.
Viers, J.] Univ Toulouse, GET CNRS UMR 5563, F-31400 Toulouse, France
[Pokrovsky, O. S.] UroRAS, Inst Ecol Problems North, Arkhangelsk, Russia
[Reynolds, B. C.] Swiss Fed Inst Technol, Inst Geochem & Petr, Zurich, Switzerland
[Prokushkin, A. S.] RAS, Inst Forest, Siberian Branch, Krasnoyarsk, Russia
Доп.точки доступа:
Pokrovsky, O.S.; Reynolds, B.C.; Prokushkin, A. S.; Прокушкин, Анатолий Станиславович; Schott, J.; Viers, J.; BIO-GEO-CLIM Mega-grant of the Ministry of Education and Science of the Russian Federation; Tomsk State University [14.B25.31.0001]; ANR "Arctic Metals"; GDRI CAR WET SIB and LIA LEAGE International Laboratories [RFFI 10-05-92513, 11-04-10056]; CRDF [RUG1-2980-KR-10]; Program of Presidium RAS [12-P-5-1021]; Program of Presidium UrORAS [12-U-5-1034]