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Effects of sample drying on element forms in lake sediments

机译：样品干燥对湖泊沉积物中元素形态的影响

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The application of a sequential extraction scheme provides information on the phase association of elements in a sample, such phases being described, for example, as ‘exchangeable/adsorbed’, ‘amorphous Fe/Al oxides’ and ‘soluble organics’. It is therefore critical to maintain the chemistry of a sample from the time of collection to its analysis and during its preparation for analysis. This paper focuses on the redistribution of elements, amongst five operationally defined phases, that occurs on air-drying of the sample; the effect of subsequent storage of the sample is not addressed. Two lake sediment cores (‘Green Lake’, 31 cm, and ‘Gravel Pit Lake’, 19 cm) were sampled at 1-cm intervals and divided into two sets immediately prior to sequential leach analysis of the ‘wet’ sample. The other set was air-dried prior to sequential leach analysis. Most of the 39 elements determined in the Green Lake sediment showed, on drying, a redistribution to more labile forms. For example, increases in Fe concentration in the oxide phases were observed with a concomitant decrease in the crystalline forms of Fe reporting to the final aqua regia digestion. These changes are generally small in magnitude (<10% of the total element extracted) but they can change the shape of the element profile down the core for an affected leach which in turn could lead to misinterpretation of the sequential leach data. Surprisingly, S did not show any changes on drying, suggesting that the kinetics of oxidation are reasonably slow and that storage of the sample rather than drying is more important. The fact that some elements in the Gravel Pit Lake core behaved differently to Green Lake indicates that redistribution of elements on sample drying is both element and matrix dependent.
机译：顺序提取方案的应用提供了有关样品中元素的相缔合的信息 ，例如，这些相 被描述为“可交换/吸附”，“ “非晶态Fe / Al氧化物”和“可溶性有机物”。 因此，从样品采集到保存的整个过程中，保持样品 的化学性质至关重要。分析并在准备过程中 进行分析。本文着重讨论了在样品的风干 上发生的五个操作定义的阶段中元素的重新分配， ；没有解决样本 的后续存储的影响。以1 cm的间隔对两个湖泊沉积物岩心（“ sup> 31 cm和” Gravel Pit Lake” 19 cm）进行采样，并以1 cm的间隔进行采样，并立即分为两组先用 进行“湿”样品的连续浸出分析。 另一组在进行连续浸出分析之前进行风干。 这39个中的大多数干燥后，绿湖沉积物中 中确定的元素显示出重新分配为更不稳定的形式。对于 示例，观察到 氧化物相中的Fe浓度增加，同时报告最终王水的Fe的结晶形式 随之减少。消化。这些变化 通常幅度较小（<提取的总元素 的10％），但是它们可以更改元素轮廓的形状 受影响浸出的核心，这反过来可能导致 误解顺序浸出数据。令人惊讶的是， S在干燥时没有任何变化，这表明氧化的动力学 相当慢，并且样品 的储存而不是干燥更重要。 Gravel Pit Lake岩心中某些元素 的行为不同于Green Lake 的事实表明元素干燥时元素的重新分布是元素和基质的 依赖。

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