Mapping of uranium and phosphorus in sediments of Lakes Baikal and Issyk-Kul by neutron-induced autoradiography

Жмодик, С. М.; Верховцева, Н. В.; Mironov, A. G.; Ilić, R.; Nemirovskaya, N. A.; Khlystov, Oleg; Klerkx, J.; Zhmodik, Alexey

doi:10.1016/s1350-4487(03)00204-x

Cited by 7 publications

(2 citation statements)

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“…The affinity of U to be incorporated into phosphate minerals, with the potential to form stable uranyl phosphate minerals (Jerden and Sinha, 2003;Ohnuki et al, 2004;Wellman et al, 2007), can lead to highly elevated U contents (up to 250 µg g -1 ; Altschuler et al, 1958;Bird, 2012). Indeed, previous geochemical analysis of Lake Baikal sediments showed that intervals enriched in phosphate minerals (especially vivianite) exhibit U concentrations of up to 90 µg g -1 (Zhmodik et al, 2003;; see also Fagel et al, 2005), at least one order of magnitude higher than in most marine sediments (Plank and Langmuir, 1998). Hence, U association with phosphate minerals can further U enrichment.…”

Section: The Relationship Between Uranium and Phosphorusmentioning

confidence: 99%

“…concentrations down to the lake bottom and into the top sediment layer, it has been shown that sedimentary U contents can reach more than 20 µg g -1 (Petrov et al, 1999;Zhmodik et al, 2003Zhmodik et al, , 2005Chebykin et al, 2004Chebykin et al, , 2007Goldberg et al, 2005), i.e. about 5 times higher than the rocks of Lake Baikal's watershed (Jahn et al, 2009;Litvinovsky et al, 2011).…”

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confidence: 99%

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Elevated uranium concentrations in Lake Baikal sediments: Burial and early diagenesis

et al. 2016

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The water column of Lake Baikal (Siberia) is pervasively oxic and O 2 penetrates several cm into the sediment, followed by distinct layers of Fe/Mn oxide that undergo reductive-dissolution/oxidativeprecipitation cycles. Uranium (U) contents of the oxic surface sediment layers were ~15 µg g-1 , which is unparalleled in oxygenated lakes. To understand the processes leading to this enrichment we investigated the geochemical composition of the particulate matter and pore water of four sediment cores from different locations in the lake and performed mass balance calculations based on sediment mass accumulation rates and published loads from major tributaries. The comparison of loads and export of U in Lake Baikal suggested that current estimates of loads are too low by a factor of about 3 compared to sediment mass accumulation rates. Peak loads during spring ice melt in tributaries that are difficult to monitor and quantify might be the main cause for the deviation. The high U concentrations in the lake sediments originated from the scavenging of U in the water column through association with settling organic particles and particulate Fe(III)-and, to a lesser extent, Mn(IV)-oxides. We outline the hypothesis that two distinct U phases, lithogenic and non-lithogenic U reach the lake sediment and that authigenic U is subsequently formed under reducing conditions within the sediment. In some cores we found that most U was remobilized during the degradation of organic matter, in particular within the top oxygenated layer of the sediment. Significant enrichments prevailed due to U adsorption to and/or co-precipitation with Fe-oxides. When Feoxides and, to a lesser extent, Mn-oxides were reductively dissolved, they released U to the pore water, leading to peak dissolved U concentrations in the anoxic sediment, which in turn, precipitated as authigenic U under predominantly sulphate-reducing conditions. The onset of the accumulation of authigenic U coincided with the formation of distinct Fe/Mn oxide layers above. We argue that the resilience of Fe-oxides (especially crystalline goethite and hematite), in association with phosphate, even within reducing (but non-sulfidic) sediments support the burial of substantial amounts of U.

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