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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >The influence of particle composition and particle flux on scavenging of Th, Pa and Be in the ocean
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The influence of particle composition and particle flux on scavenging of Th, Pa and Be in the ocean

机译：颗粒组成和颗粒通量对海洋中Th，Pa和Be清除的影响

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We have examined the relative affinity of Th, Pa and Be for sorption from seawater onto particles of varible composition (opal, carbonate, lithogenic particles and organic carbon). Nuclide concentrations in particles collected from time-series sediment traps were normalized by the dissolved nuclide concentration in the overlying water column in order to compute partition coefficients under conditions spanning a wide range of particle flux and particle composition. Our results suggest that the affinity of particles for Pa and Be increases with their increasing opal content and decreasing carbonate content, while the affinity of particles for Th increases with increasing carbonate content, and decreases with increasing opal content. We find no correlation between the aluminosilicate content of particles and their affinity for scavenging of any of these elements. Extrapolating to a pure CaCO_3 end member, the partition coefficient for Th (9.0 * 10~6 g g~(-1) is ～40 times greater than for Pa, and roughly 100 times greater than for Be, whereas for a pure opal end member, the partition coefficient for Th (3.9 * 10~5 g g~(-1)) is slightly less than that for Pa and Be. Partition coefficients decrease with increaisng particle flux in open-ocean settings, but not in an oceanmargin region. This kinetic effect reflects the increasing contribution of unaltered surface material reaching the sediment traps as particle flux increases. The degree of fractionation between Pa and Th and between Be and Th depends on the opal:carbonate rain ratio. These results challenge the use of sedimentary ~(231)Pa/~(230)Th and ~(10)Be/~(230)Th ratios as simple proxies of particle flux. However, the strong dependence of nuclide scavenging on the opal:carbonate rain ratio may provide a needed tool for reconstructing past changes in planktonic community composition.
机译：我们已经研究了Th，Pa和Be对海水从海水中吸附到组成可变的颗粒（蛋白石，碳酸盐，成岩颗粒和有机碳）上的相对亲和力。从时间序列沉积物收集器收集的颗粒中的核素浓度通过上覆水柱中的溶解核素浓度进行归一化，以便计算在宽范围的颗粒通量和颗粒组成条件下的分配系数。我们的结果表明，颗粒对Pa和Be的亲和力随蛋白石含量的增加和碳酸盐含量的减少而增加，而对Th和Th的亲和力随碳酸盐含量的增加而增加，而随着蛋白石含量的增加而降低。我们发现颗粒的硅铝酸盐含量与它们清除这些元素中任何一种的亲和力之间没有关联。推算到纯CaCO_3末端成员，Th（9.0 * 10〜6 gg〜（-1）的分配系数是Pa的40倍，是Be的大约100倍，而纯蛋白石末端的，Th的分配系数（3.9 * 10〜5 gg〜（-1））略小于Pa和Be的分配系数，在开放海洋环境中，分配系数随颗粒通量的增加而减小，而在海洋边缘区域则不然。动力学效应反映了随着颗粒通量的增加，未改变的表层物质到达沉积物捕集阱的贡献增加，Pa和Th之间以及Be和Th之间的分馏程度取决于蛋白石：碳酸盐雨比，这些结果对沉积物〜（ 231）Pa /〜（230）Th和〜（10）Be /〜（230）Th之比是颗粒通量的简单近似值，但核素清除率对蛋白石/碳酸盐雨比的强烈依赖性可能为重建过去浮游生物群落组成的变化。

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