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

IF 0.9 4区 地球科学 Q4 GEOCHEMISTRY & GEOPHYSICS
Alexander V Dubinin, Elena O Dubinina, Tatyana P Demidova, Nataliya M Kokryatskaya, Maria N Rimskaya-Korsakova, Sofia A Kosova, Evgeniy V Yakushev
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引用次数: 9

Abstract

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.

Abstract Image

黑海底部对流层均匀性的稳定同位素证据
黑海是地球上最大的新生盆地。缺氧区由上层按密度分层的水团和下层相对密度均匀化的水团(深度>1750 m)组成,称为底层对流层。为了评估底部对流层上下边界的均匀性和可能的物质交换,获得了S、O和H稳定同位素组成的新数据。样本于2008年8月和2009年3月从位于黑海中东部的两个站点采集。整个水柱的δ18O和δD值的分布没有季节变化。在背斜区(水深200 ~ 400 m)和底部以上5 m的BCL, δD值变化有明显的差异,这可能是由于陆架修饰地中海水升高部分侵入物的侵入造成的。观测到的δ18O(或δD)与盐度的线性关系表明,水盐混合同时发生,黑海深水有两个端部:高盐度地中海海水和淡水输入。底部对流层平均δ34S (H2S)为-40.6±0.5‰,没有季节变化。在底部(depth >2000 m), 34S损耗低至-41.0‰。我们的δ34S (SO4)数据比底部对流层的实测数据高2 ~ 3‰。好氧带的硫酸盐δ34S (SO4) = +21‰,为海水硫酸盐,未发生硫酸盐还原。深度>平均δ34S (SO4)值;1250 m为+23.0±0.2‰(1σ)。硫酸盐的硫同位素组成在底部对流层及其上下边界没有变化,也不取决于观测季节。
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来源期刊
Geochemical Transactions
Geochemical Transactions 地学-地球化学与地球物理
CiteScore
3.70
自引率
4.30%
发文量
2
审稿时长
>12 weeks
期刊介绍: Geochemical Transactions publishes high-quality research in all areas of chemistry as it relates to materials and processes occurring in terrestrial and extraterrestrial systems.
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