In this work, we applied X-ray Absorption Spectroscopy (XAS) and selective leaching experiments for investigating iron speciation in different dust advections collected on different unwashed quartz fiber filters. XAS analysis evidenced a predominance of Fe(III) in 6-fold coordination for Saharan dust and a trend towards Fe(II) and 4-fold coordination in the order: Saharan dust, mixed Saharan, and non-Saharan aerosol samples. The role of the sampling substrate was evaluated explicitly, including in the analysis a set of blank filters. We were able to pinpoint the possible contribution to the overall XAS spectrum of the residual Fe on quartz as the concentration decrease towards the blank value. In particular, the filter substrate showed a negligible effect on the structural trend mentioned above. Furthermore, selective leaching experiments evidenced a predominance of the residual fraction on Fe speciation and indicated the lowest Fe concentrations for which the blank contribution is <20% are 1 $\mathsf{\mu }$ g for the first three steps of the procedure (releasing the acid-labile, reducible and oxidizable phases, respectively) and 10 $\mathsf{\mu }$ g for the last step (dissolving the insoluble residuals).

中文翻译：

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不同撒哈拉尘埃对流中的铁形态以及程序空白对X射线吸收光谱法和选择性浸出实验结果的影响

在这项工作中，我们应用了X射线吸收光谱（XAS）和选择性浸出实验，以研究在不同的未清洗石英纤维滤池上收集的不同尘埃对流中的铁形态。XAS分析证明，Fe（III）在撒哈拉尘埃的6倍配位中占优势，并且在Fe（II）和4倍配位的趋势中依次为：撒哈拉尘埃，混合撒哈拉和非撒哈拉气溶胶样品。明确评估了采样基质的作用，包括在分析中包括一组空白滤光片。我们能够确定出随着浓度降低到空白值，石英上残留铁对整个XAS光谱的可能贡献。特别地，过滤器基板对上述结构趋势的影响可忽略不计。此外， $\mathsf{\mu }$ g对于该程序的前三个步骤（分别释放酸不稳定的，可还原的和可氧化的相）和10 $\mathsf{\mu }$ g用于最后一步（溶解不溶残留物）。