Fe redox cycling in Iberian continental margin sediments (NE Atlantic)
Fe redox cycling in Iberian continental margin sediments (NE Atlantic)
复制标题
伊比利亚大陆边缘沉积物中的铁氧化还原循环（大西洋东北部）
DOI：
10.1357/002224002321505165
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发表时间：
2002
影响因子：
0.5
通讯作者：
W. Helder
中科院分区：
文献类型：
--
作者：
C. V. D. Zee;W. V. Raaphorst;W. Helder
本文介绍了伊比利亚边缘纳扎尔峡谷等4条横坡断面沉积物中孔隙水Fe2+、铁锌可提取Fe2+和固相铁的垂直分布情况。吸附的Fe2+不能直接测量，在操作上定义为可以用亚铁氮萃取的部分。我们的目标是(1)研究Fe2+吸附在铁氧化还原循环中的潜在作用，(2)对铁氧化还原循环进行量化，(3)确定其速率限制因素，重点是坡面和峡谷内站点之间的差异。在所有沉积物中，孔隙水中Fe2+和Fe2+可浸提态Fe2+浓度随着深度的增加而同时增加，直到达到最大值后，孔隙水中Fe2+浓度迅速下降，这可能是由于以铁-硫化物的形式沉淀。然而，Ferozine可提取的Fe2+浓度随着沉积物的深入而缓慢下降或保持不变，这表明吸附表面的反应正在进行，或者解吸比吸附动力学慢得多。在Fe还原时，Fe2+被释放到孔隙水中，在那里它直接沉淀和/或吸附到沉积物基质的可用表面，包括有机质。吸附作用延缓了自生亚铁矿物的形成，使Fe2+向沉积物中运移得更深。在那里，吸附的Fe2+可作为自生亚铁矿物形成的深部来源。建立了一个简单的稳态模型，该模型将Fe2+吸附作为一级动力学反应来估算Fe的反应速率。有机碳矿化率高的陆架上，Fe的氧化还原速率最强，且随水深的增加而减小。在沉积通量高的峡谷中，Fe的反应速率随着水深的增加而增加，在峡谷底部3097m处达到最大值，在4280m处又下降到深海。氧化层和还原层中的孔隙水Fe2+、可提取Fe2+和固相Fe的周转时间估计表明，沉积物混合是伊比利亚边缘所有站点Fe循环的最重要的速率限制因素。在主断面104m和113m站，Fe还原对有机质矿化的贡献率为5%，在峡谷底部3097m站，Fe还原对有机质矿化的贡献为6%。在其他站位，Fe还原对有机质矿化的贡献不到4%。
In this paper, data are presented on the vertical distribution of pore water Fe 2+ , ferrozine-extractable Fe 2+ and solid phase Fe in sediments along four across-slope transects including the Nazare canyon at the Iberian margin. Sorbed Fe 2+ cannot be measured directly and is operationally defined as the fraction that can be extracted with ferrozine. Our objectives were (1) to investigate the potential role of Fe 2+ sorption in the Fe redox cycle, (2) to quantify Fe redox cycling and (3) to determine its rate limiting factors, with emphasis on differences between stations across the slope and in the canyon. In all sediments pore water Fe 2+ and ferrozine-extractable Fe 2+ concentrations increased simultaneously with depth until a maximum was reached and upon which the pore water Fe 2+ concentration rapidly declined, presumably due to precipitation as iron-sulfide. The ferrozine-extractable Fe 2+ concentration, however, either slowly diminished or remained unchanged when going deeper into the sediment, suggesting ongoing reaction at the sorption surfaces or much slower desorption than adsorption kinetics. Upon Fe reduction, Fe 2+ is released into the pore water where it either directly precipitates and/or adsorbs onto available surfaces of the sediment matrix, including organic matter. Through sorption, authigenic ferrous mineral formation is delayed and Fe 2+ may be transported deeper into the sediment. There, sorbed Fe 2+ can act as a deep source for authigenic ferrous mineral formation. A simple steady-state model was formulated that includes Fe 2+ sorption as a first-order kinetic reaction to estimate Fe reaction rates. Fe oxidation and reduction rates were most intense at the shelf, where organic carbon mineralization rates are high, and decreased with water depth. In the canyon, where deposition fluxes were high, Fe reaction rates increased with water depth until a maximum at the foot of the canyon at 3097 m and decreased again to the abyssal at 4280 m. Turnover times estimated for pore water Fe 2+ , ferrozine-extractable Fe 2+ and solid phase Fe both in the oxidized and reduced layer indicated that sediment mixing was the most important rate limiting factor for Fe cycling at all stations of the Iberian margin. The contribution of Fe reduction to organic matter mineralization was 5% at the 104-m and 113-m stations on the main transect and 6% at the 3097-m station at the foot of the canyon. At the other stations Fe reduction contributed less than 4% to the mineralization of organic matter.