Industrial emissions of lanthanides to aquatic ecosystems increase, but knowledge of the environmental fate of these metals is limited. Here we focus attention upon the distribution of lanthanides in freshwater ecosystems, describing lanthanide partitioning between sediment, water and biota. Since lanthanides are often used as oxidation-state analogues for actinides, their distribution can reflect long-term behaviour of the radioactive transuranics. Concentrations of all 14 naturally occurring lanthanides were measured by ICP-MS in Sago pondweed (Potamogeton pectinatus), common duckweed (Lemna minor), seven different mollusc species (tissue and shell), two sediment fractions (< 2 mm and < 63 microm), surface water and sediment pore water from five locations in The Netherlands. In all samples, the typical 'saw-tooth' lanthanide pattern was observed, which implies that lanthanides are transported as a coherent group through aquatic ecosystems. Typical deviations from this pattern were found for Ce and Eu and could be explained by their redox chemistry. The variation in concentrations in abiotic fractions was limited, i.e. within one order of magnitude. However, variations of up to three orders of magnitude were observed in biotic samples, suggesting different affinities among organisms for lanthanides as a group, with significant differences only among molluscs and pondweed samples in relation to sampling location. For P. pectinatus it was shown that pore water was the most important lanthanide source, and for snails, food (plants) seems to be the dominant lanthanide source. Lanthanides were not equally distributed between mollusc shell and tissue and the ratio of lanthanide concentrations in shell and tissue were dependent on the sampling location. Shells contained much lower concentrations and were relatively enriched in Eu, and to a lesser extent in Ce. Bioconcentration factors for lanthanides in plants and snails relative to surface water were typically between 10000 and 100000 l x kg(-1) dry matter, while sediment-water partition coefficients were between 100000 and 3000000 l x kg(-1) dry matter. There was a low extent of biomagnification in the plant-to-snail system, with a maximum biomagnification factor of 5.5. Many distribution coefficients displayed a slight decrease with atomic number. This can be attributed to the general increase in ligand stability constants with atomic number, keeping the heavier lanthanides preferentially in solution.

中文翻译：

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淡水植物和软体动物中的镧系元素浓度与地表水，孔隙水和沉积物中的浓度有关。荷兰的一个案例研究。

镧系元素向水生生态系统的工业排放量增加，但是对这些金属的环境命运的了解有限。在这里，我们集中注意镧系元素在淡水生态系统中的分布，描述镧系元素在沉积物，水和生物区系之间的分配。由于镧系元素经常被用作act系元素的氧化态类似物，因此它们的分布可以反映出放射性超铀化合物的长期行为。ICP-MS测定了西米塘草（Potamogeton pectinatus），普通浮萍（Lemna minor），七种软体动物种类（组织和壳），两个沉积物组分（<2 mm和<63 microm）中所有14种天然镧系元素的浓度，来自荷兰五个地区的地表水和沉积物孔隙水。在所有样本中，典型的“锯齿” 观察到镧系元素的格局，这意味着镧系元素作为一个连贯的群体通过水生生态系统进行运输。对于Ce和Eu，发现了与该模式的典型偏差，可以用它们的氧化还原化学来解释。非生物组分中浓度的变化是有限的，即在一个数量级之内。但是，在生物样品中观察到的变化高达三个数量级，这表明生物体之间对镧系元素的亲和力不同，只有软体动物和紫菜样品之间的采样位置显着不同。对于果蝇（P.pectinatus）而言，孔隙水是最重要的镧系元素来源，而对于蜗牛而言，食物（植物）似乎是镧系元素的主要来源。镧系元素在软体动物的外壳和组织之间分布不均，外壳和组织中镧系元素的浓度比取决于采样位置。贝壳的浓度要低得多，并且相对富集在Eu中，而Ce则较少。相对于地表水，植物和蜗牛中镧系元素的生物浓缩系数通常在10000至100000 lx kg（-1）干物质之间，而沉积物-水分配系数在100000至3000000 lx kg（-1）干物质之间。植物-蜗牛系统的生物放大率较低，最大生物放大系数为5.5。许多分布系数随原子序数显示略有下降。这可以归因于配体稳定常数随原子序数的普遍增加，