Stable isotope evidence for the Bottom Convective Layer homogeneity in the Black Sea

Geochemical Transactions

Research Article

Nataliya M Kokryatskaya¹  Sofia A Kosova²  Elena O Dubinina³  Evgeniy V Yakushev⁴  Alexander V Dubinin⁵  Tatyana P Demidova⁵  Maria N Rimskaya-Korsakova⁵ 

[1] Institute of Environmental Problems of the North, Russian Academy of Sciences, nab. Severnoy Dviny, 23, 163000, Arkhangelsk, Russia;Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry, Russian Academy of Sciences, Staromonetniy per. 35, 119017, Moscow, Russia;Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry, Russian Academy of Sciences, Staromonetniy per. 35, 119017, Moscow, Russia;University of Johannesburg, Auckland Park Kingsway Campus, P.O. Box 524, Johannesburg, Republic of South Africa;Norwegian Institute for Water Research, Gaustadalleen 21, No-0349, Oslo, Norway;PP Shirshov Institute of Oceanology, Russian Academy of Sciences, Nahimovskiy prospect, 36, 117997, Moscow, Russia;

关键词: Black Sea;    Hydrogen sulfide;    Sulfate;    Sulfur isotopes;    Oxygen isotopes;    Hydrogen isotopes;    Bottom Convective Layer;    Sulfate reduction;   

DOI  :  10.1186/1467-4866-15-3

 received in 2013-08-23, accepted in 2014-04-09,  发布年份 2014

来源: Springer

【 摘 要 】

The Black Sea is the largest euxinic basin on the Earth. The anoxic zone consists of the upper part water mass stratified by density, and the lower water mass homogenized relative to density (depth >1750 m), named the Bottom Convective Layer. To assess homogeneity and possible exchange of matter across the upper and lower boundaries of the Bottom Convective Layer, new data on stable isotope composition of S, O and H were obtained. Samples were collected in August 2008 and March 2009 from two stations located in the eastern central part of the Black Sea.Distribution of δ18O and δD values of water for the entire water column did not vary seasonally. Appreciable differences were marked for δD value variation in the picnocline area (water depth 200-400 m) and in the BCL 5 m above the bottom that might be caused by penetration of intrusions with elevated portion of shelf modified Mediterranean Water. Observed linear relationship between δ18O (or δD) and salinity indicates that mixing water and salt occurs at the same time, and the deep water of the Black Sea has two end members: the high-salinity Mediterranean seawater and freshwater input.In the Bottom Convective Layer, the average δ34S (H2S) was -40.6 ± 0.5‰ and did not vary seasonally. At the bottom (depth > 2000 m), 34S depletion down to –41.0‰ was observed. Our δ34S (SO4) data are by 2-3‰ higher than those measured previously for the Bottom Convective Layer. Sulfate from the aerobic zone with δ34S (SO4) = +21‰ corresponds to ocean water sulfate and that has not been subjected to sulfate reduction. Average δ34S (SO4) values for depths > 1250 m were found to be +23.0 ± 0.2‰ (1σ). Sulfur isotope composition of sulfate does not change in the Bottom Convective Layer and on its upper and lower boundaries, and does not depend on the season of observation.

【 授权许可】

CC BY   
© Dubinin et al.; licensee BioMed Central Ltd. 2014. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited.