Insights into the transfer of silicon isotopes into the sediment record
Insights into the transfer of silicon isotopes into the sediment record
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DOI：
10.5194/bg-13-147-2016
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发表时间：
2016-01-01
期刊：
影响因子：
4.9
通讯作者：
Horstwood, M. S. A.
中科院分区：
文献类型：
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作者：
Panizzo, V. N.;Swann, G. E. A.;Horstwood, M. S. A.
第一个三角洲Si-30（硅藻）数据从湖泊沉积物陷阱，西伯利亚贝加尔湖。数据进行了比较，与3月地表水（上180米）三角洲Si-30（DSi）的组成，其平均值为+2.28份每千+/- 0.09（95%的置信度）。该值用作沃茨的硅藻水华前基线硅酸同位素组成（δ Si-30（DSi）（初始））。2012年至2013年期间，沿贝加尔湖南盆地水柱的深度沿着部署了开放式捕集器。硅藻组合显示出春季/夏季水华物种尖针杆藻弧度变种的优势（> 85%），因此δ Si-30（硅藻）组成主要反映了春季/夏季水华的利用。从开放式捕集器中分离硅藻，此外，从3个月（测序）捕集器（2012年5月、7月和8月）中分离硅藻，用于δ Si-30（硅藻）分析。开放捕集器的平均δ Si-30（硅藻）值为+1.23 ‰ +/-0.06（95%置信度和MSWD为2.9，n = 10）。2012年6月，总干物质沉积物通量最高，这是由于占主导地位的春季硅藻水华的初始出口。因此，我们认为，五月三角洲Si-30（硅藻）签名（+ 0.67% +/- 0.06; 2西格玛）相比，平均上层水三角洲Si-30（DSi）初始（如预开花）的签名可以用来提供一个快照估计硅藻吸收（摄取）分馏因子（吸收（摄取））在贝加尔湖。因此，得出了-1.61%的DSi（吸收）估计值，尽管我们强调需要同步的每月δ Si-30（DSi）和δ Si-30（硅藻）数据来提供更可靠的估计，因此需要更严格地测试这一点，特别是考虑到随着水华持续存在，DSi池的任何逐步富集。开放式圈闭中近乎恒定的三角洲Si-30（硅藻）组成表明，通过水柱的信号得到了充分保存，从而证明了该技术在地球化学和古环境研究中的使用和应用是合理的。最后将数据与从南部盆地采集的湖泊沉积物岩心样品进行了比较。对于芯BAIK 13 -1C（芯深0.6-0.8 cm）和BAIK 13 -4F（芯深0.2-0.4 cm），分别得出+1.30份/千份+/-0.08（2 σ）和+1.43%+/-0.13（2 σ）的值。陷阱数据突出的分馏因素与硅藻溶解（溶解）（特别是针杆藻，在陷阱中的优势类群，是非常容易溶解）的情况下，在水柱和湖泊表层沉积物，从而验证三角洲Si-30（硅藻）分析在贝加尔湖和其他淡水系统中的应用，在palaeoreconstructions。
The first delta Si-30(diatom) data from lacustrine sediment traps are presented from Lake Baikal, Siberia. Data are compared with March surface water (upper 180 m) delta Si-30(DSi) compositions for which a mean value of + 2.28 parts per thousand +/- 0.09 (95% confidence) is derived. This value acts as the pre-diatom bloom baseline silicic acid isotopic composition of waters (delta Si-30(DSi) (initial)). Open traps were deployed along the depth of the Lake Baikal south basin water column between 2012 and 2013. Diatom assemblages display a dominance (> 85 %) of the spring/summer bloom species Synedra acus var radians, so that delta Si-30(diatom) compositions reflect predominantly spring/summer bloom utilisation. Diatoms were isolated from open traps and, in addition, from 3-monthly (sequencing) traps (May, July and August 2012) for delta Si-30(diatom) analyses. Mean delta Si-30(diatom) values for open traps are + 1.23 parts per thousand +/- 0.06 (at 95% confidence and MSWD of 2.9, n = 10). Total dry mass sediment fluxes are highest in June 2012, which we attribute to the initial export of the dominant spring diatom bloom. We therefore argue that May delta Si-30(diatom) signatures (+ 0.67% +/- 0.06; 2 sigma) when compared with mean upper water delta Si-30(DSi) initial (e.g. pre-bloom) signatures can be used to provide a snapshot estimation of diatom epsilon(uptake) fractionation factors (epsilon(uptake)) in Lake Baikal. A epsilon(uptake) estimation of -1.61% is therefore derived, although we emphasise that synchronous monthly delta Si-30(DSi) and delta Si-30(diatom) data would be needed to provide more robust estimations and therefore more rigorously test this, particularly when taking into consideration any progressive enrichment of the DSi pool as blooms persist. The near-constant delta Si-30(diatom) composition in open traps demonstrates the full preservation of the signal through the water column and thereby justifies the use and application of the technique in biogeochemical and palaeoenvironmental research. Data are finally compared with lake sediment core samples, collected from the south basin. Values of + 1.30 parts per thousand +/- 0.08 (2 sigma) and + 1.43% +/- 0.13 (2 sigma) were derived for cores BAIK13-1C (0.6-0.8 cm core depth) and at BAIK13-4F (0.2-0.4 cm core depth) respectively. Trap data highlight the absence of a fractionation factor associated with diatom dissolution (epsilon(dissolution)) (particularly as Synedra acus var radians, the dominant taxa in the traps, is very susceptible to dissolution) down the water column and in the lake surface sediments, thus validating the application of delta Si-30(diatom) analyses in Lake Baikal and other freshwater systems, in palaeoreconstructions.