Understanding the origins of aerosol iron (Fe) is crucial for comprehending its influence on Earth's climate and the global biogeochemical cycle. Fe isotopes (δ56Fe) serve as a distinctive and effective tool for constraining aerosol Fe sources and transport routes. In this work, we comprehensively compiled a global dataset (n = 195) of recent aerosol Fe isotopes, spanning diverse atmospheric environments such as urban areas, remote glacier areas, and oceans in order to elucidate the distribution of aerosol Fe isotopes and conduct a quantitative assessment of atmospheric Fe sources on a global scale. We first summarized the spatiotemporal distribution of aerosol δ56Fe and its partitioning pattern in various aerosol size fractions. On the spatial scale, the field observations of aerosol Fe isotopes were predominantly concentrated in the Northern Hemisphere locations. Aerosol δ56Fe exhibited a pronounced decreasing trend from glaciers to oceans to human-influenced urban areas. On the temporal change, aerosol δ56Fe showed lower values during non-dust periods compared to those of dust periods, along with greater variability. The partitioning pattern of δ56Fe in various aerosol size fractions is characterized by a notable enrichment of lighter isotopes in PM2.5 compared to that of bulk samples and PM>2.5. Secondly, the current quantification study of aerosol Fe sources using Fe isotopes remains uncertain due to the exclusion of heavy-isotope anthropogenic endmembers in calculations. Therefore, here we re-categorized the global aerosol-Fe sources into three endmembers along with their representative δ56Fe values, including natural dust (0.09 ± 0.03 ‰), steel smelting+automobile exhaust (−2.9 ± 1.3 ‰), as well as coal combustion (0.46 ± 0.16 ‰). Finally, utilizing the MixSIAR model and complied isotope dataset, we identified coal combustion as the predominant anthropogenic source of aerosol Fe on the hemisphere scale. To enhance our understanding of the atmospheric Fe cycle, future research will necessitate broader large-scale observations of aerosol Fe isotopes, with a particular emphasis on the Southern Hemisphere.

中文翻译：

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使用稳定铁同位素对气溶胶铁起源的全球尺度限制：综述


了解气溶胶铁 （Fe） 的来源对于理解其对地球气候和全球生物地球化学循环的影响至关重要。Fe 同位素 （δ56Fe） 是限制气溶胶 Fe 来源和运输路线的一种独特而有效的工具。在这项工作中，我们全面编制了近期气溶胶 Fe 同位素的全球数据集 （n = 195），涵盖城市地区、偏远冰川地区和海洋等不同的大气环境，以阐明气溶胶 Fe 同位素的分布并在全球范围内对大气 Fe 来源进行定量评估。我们首先总结了气溶胶 δ56Fe 的时空分布及其在各种气溶胶尺寸分数中的分配模式。在空间尺度上，气溶胶 Fe 同位素的现场观测主要集中在北半球位置。气溶胶 δ56Fe 表现出从冰川到海洋再到受人类影响的城市地区的明显下降趋势。在时间变化上，与尘埃期相比，非尘埃期的气溶胶 δ56Fe 值较低，并且变化更大。δ56Fe 在各种气溶胶尺寸分数中的分配模式的特点是，与大块样品和 PM>2.5 相比，PM2.5 中较轻的同位素显着富集。其次，由于计算中排除了重同位素人为终元，目前使用 Fe 同位素对气溶胶 Fe 源的定量研究仍不确定。因此，我们将全球气溶胶-Fe 来源及其代表性的 δ56Fe 值重新分类为三个端元，包括自然尘埃 （0.09 ± 0.03 ‰）、钢铁冶炼 + 汽车尾气 （-2.9 ± 1.3 ‰） 以及煤炭燃烧 （0.46 ± 0.16 ‰）。 最后，利用 MixSIAR 模型和合成同位素数据集，我们确定煤炭燃烧是半球尺度上气溶胶 Fe 的主要人为来源。为了加强我们对大气 Fe 循环的理解，未来的研究将需要对气溶胶 Fe 同位素进行更广泛的大规模观测，特别强调南半球。