To explore the freezing effect on iron (Fe) solubility in natural environments, especially in Polar regions, event based freshly fallen snow samples were collected at Newark, New Jersey on the US East Coast for two consecutive winter seasons (2014–2015 and 2015–2016). These samples were analyzed for the concentrations of soluble iron (Fesol) using UV-Vis Spectroscopy and filterable iron (Fefil) and total iron (Fetot) using Atomic Absorption Spectroscopy. The average fractional solubility of the Fesol (the portion that passes through a 0.22 μm pore-size filter) with respect to the total Fe in the samples was 23.3 ± 12.2%, with the majority of the soluble Fe being present as Fe(III). Approximately 48.5% of the total Fe existed as Fefil (the portion that passes through 0.45 μm pore size filter media). No significant correlation was found between the soluble ionic species and soluble Fe. Six snow events were kept frozen for 10 days, and analyzed in periodic intervals to study the post-freezing modification in Fe solubility. Events 1 and 2 showed increasing trend in the soluble Fe concentrations; however, the events 5, 6, 7, and 8 showed no noticeable increments. The pattern shown in Events 1 and 2 is associated with high fraction of Fefil and one unit pH drop, suggesting that the freeze-induced modification in Fe solubility could be linked with the amount of Fefil and the acidity change in the samples. To further investigate the freeze-induced compaction of particles, samples from three events 6, 7, and 10 were analyzed by SEM-STEM-EDS microscopy, and the results showed that due to freezing, in general, the particles in the ice-melt counterparts tend to compact and cluster and form larger aggregates compared to the particles in snow-melt. These results show, despite the freeze-induced compaction in snow was observed from STEM images, the snow freezing might not have significant effect in increasing Fe solubility from materials in the snow. These results further suggest that freezing process with fresh snow in high-latitude regions may not impose significant modification on Fe solubility in snow.

中文翻译：

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冻结和压实对天然雪中铁溶解度的影响不显着

为了探索冻结对自然环境中铁 (Fe) 溶解度的影响，尤其是在极地地区，我们在美国东海岸的新泽西州纽瓦克连续两个冬季（2014-2015 和 2015-）收集了基于事件的新降雪样本。 2016）。使用紫外-可见光谱法分析这些样品的可溶性铁 (Fesol) 的浓度，使用原子吸收光谱法分析可过滤铁 (Fefil) 和总铁 (Fetot) 的浓度。Fesol（通过 0.22 μm 孔径过滤器的部分）相对于样品中总 Fe 的平均分数溶解度为 23.3 ± 12.2%，其中大部分可溶性 Fe 以 Fe(III) 形式存在. 大约 48.5% 的总 Fe 以 Fefil（通过 0.45 μm 孔径过滤介质的部分）形式存在。在可溶性离子物质和可溶性 Fe 之间没有发现显着的相关性。六个雪事件被冻结 10 天，并定期进行分析以研究冻结后 Fe 溶解度的变化。事件 1 和事件 2 的可溶性 Fe 浓度呈上升趋势；然而，事件 5、6、7 和 8 没有显示出明显的增加。事件 1 和 2 中显示的模式与高比例的 Fefil 和一个单位的 pH 值下降有关，这表明冷冻诱导的 Fe 溶解度改变可能与 Fefil 的量和样品中的酸度变化有关。为了进一步研究冷冻诱导的颗粒压实，通过 SEM-STEM-EDS 显微镜分析了来自三个事件 6、7 和 10 的样品，结果表明，由于冷冻，一般来说，与融雪中的颗粒相比，冰融化对应物中的颗粒倾向于压实和聚集并形成更大的聚集体。这些结果表明，尽管从 STEM 图像中观察到雪中冻结引起的压实，但雪冻结可能对增加雪中材料的 Fe 溶解度没有显着影响。这些结果进一步表明，高纬度地区新鲜雪的冻结过程可能不会显着改变铁在雪中的溶解度。