Yttrium and lanthanides in eastern Mediterranean seawater and their fractionation during redox-cycling
Yttrium and lanthanides in eastern Mediterranean seawater and their fractionation during redox-cycling
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DOI：
10.1016/s0304-4203(96)00091-6
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发表时间：
1997-02-01
期刊：
影响因子：
3
通讯作者：
Dulski, P
中科院分区：
文献类型：
--
作者：
Bau, M;Moller, P;Dulski, P
溶解的Y和稀土元素（REE）的浓度报告从西部地中海东部的地中海沿岸盆地，缺氧的高盐度盐水和上覆的Tyro次盆地的好氧海水，后者的数据允许氧化还原循环过程中的Y和稀土元素的行为进行比较研究。所有含氧沃茨均显示页岩标准化稀土和钇（REY（SN）; Y插入Dy和Ho之间）模式，具有HREE富集、Ce-SN负异常和La-SN、Eu-SN以及最显著的Y-SN正异常。Tyro次盆地缺氧卤水中REY含量最高，HREE富集程度最低，La-SN、Eu-SN、Gd-SN、Y-SN均为正异常，Ce-SN与好氧样品形成鲜明对比（12.1）与Yb（2.7）之间存在明显的正偏差（Ce（51.2））和强烈的负偏差（Y（2.4），而Dy为4.3，Ho为3.7）。Y/Ho摩尔比从102以上下降到只有67以下的海水-盐水界面，由于优先吸附的Ho相对于Y的Fe-和Mn-羟基氧化物颗粒，最终溶解在缺氧条件下。显着的Y-Ho分馏过程中的Mn和Fe的氧化还原循环是进一步的证据，为大大降低海洋颗粒反应性的Y相比，Ho，从较低的稳定性的表面络合物的Y相对于其稀土元素的邻居。因此，Y/Ho比值似乎是颗粒对天然沃茨中溶解微量元素分布影响的敏感指标。
Concentrations of dissolved Y and rare-earth elements (REE) are reported for oxic eastern Mediterranean seawater from the western Levantine Basin, and for anoxic hypersaline brine and overlying oxic seawater from the Tyro sub-basin, the latter data allowing a comparative study of Y and REE behaviours during redox-cycling. All oxic waters show shale-normalized Rare-Earths and Yttrium (REY(SN); Y inserted between Dy and Ho) patterns with HREE enrichment, negative Ce-SN anomalies, and positive anomalies of La-SN, Eu-SN, and, most pronounced, Y-SN. The anoxic brine in the Tyro sub-basin displays the highest REY concentrations and the least HREE enrichment of all samples, and positive anomalies of La-SN, Eu-SN, Gd-SN, Y-SN, and, in marked contrast to the oxic samples, Ce-SN.Compared to overlying oxic water, the anoxic brine shows enrichment factors that decrease from La (12.1) to Yb (2.7), with a pronounced positive deviation for Ce (51.2) and a strong negative deviation for Y (2.4, compared to 4.3 for Dy and 3.7 for Ho). The Y/Ho molar ratio decreases from 102 above to only 67 below the seawater-brine interface, due to preferential sorption of Ho with respect to Y on Fe- and Mn-oxyhydroxide particles that eventually dissolve under anoxic conditions. The pronounced Y-Ho fractionation during redox-cycling of Mn and Fe is further evidence for the considerably lower marine particle reactivity of Y compared to Ho, resulting from lower stabilities of surface complexes of Y relative to those of its REE neighbours. Hence, the Y/Ho ratio appears to be a sensitive indicator of the impact of particles on the distribution of dissolved trace elements in natural waters.