Very low isotope ratio of iron in fine aerosols related to its contribution to the surface ocean
Very low isotope ratio of iron in fine aerosols related to its contribution to the surface ocean
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DOI：
10.1002/2016jd024957
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发表时间：
2016-09
期刊：
影响因子：
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通讯作者：
Minako Kurisu;Y. Takahashi;T. Iizuka;M. Uematsu
中科院分区：
文献类型：
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作者：
Minako Kurisu;Y. Takahashi;T. Iizuka;M. Uematsu
从日本广岛采集了7个粒径分级的气溶胶样品，并分析了其化学组成、铁（Fe）可溶性分数、Fe物种和Fe同位素比值。结果表明，细颗粒物中的铁比粗颗粒物包含更大比例的人为气溶胶。细颗粒中的铁比粗颗粒中的铁更易溶于模拟海水中（高达25%），并且以Fe（hydr）氧化物物种的形式存在，如水铁矿或赤铁矿。粗颗粒的δ 56 Fe同位素比值（+0.04‰ ~+0.30‰）接近地壳平均值（0.0‰）。相比之下，细颗粒的δ 56 Fe值要低得多，范围为-2.01 ‰至-0.56 ‰。细颗粒物中可溶性Fe组分的δ 56 Fe值非常低（−3.91至−1.87‰），表明人为气溶胶产生的可溶性Fe具有低δ 56 Fe值。这样低的值可以解释由动力学同位素分馏过程中的Fe在高温下蒸发，再加上铁的耐火特性。还分析了西北太平洋的海洋气溶胶。细颗粒的δ 56 Fe值也低于粗颗粒。这些结果对利用铁同位素定量估算海洋表层沉积的人为铁贡献具有重要意义。
Seven size‐fractionated aerosol samples were collected from Hiroshima, Japan, and were analyzed in terms of chemical composition, soluble fraction of iron (Fe), Fe species, and Fe isotope ratios. The results suggested that Fe in fine particles contained a larger fraction of anthropogenic aerosols than coarse particles did. Iron in the fine particles was more soluble in simulated seawater (up to 25%) than that in the coarse particles and was in the form of Fe (hydr)oxide species, such as ferrihydrite or hematite. The Fe isotope ratios (δ56Fe) of the coarse particles (+0.04‰ to +0.30‰) were close to the crustal mean value (0.0‰). By contrast, the δ56Fe values of fine particles were much lower and ranged from −2.01‰ to −0.56‰. δ56Fe values of the soluble Fe fraction in the fine particles were remarkably low (−3.91 to −1.87‰), suggesting that anthropogenic aerosols yield soluble Fe with low δ56Fe values. Such low values could be explained by kinetic isotope fractionation during evaporation of Fe at high temperatures, coupled with the refractory characteristics of Fe. Marine aerosols from the Northwest Pacific were also analyzed. The δ56Fe values in the fine particles were also lower than those in the coarse particles. These results may be important to quantitatively estimate the contribution of anthropogenic Fe deposited on the surface ocean on the basis of the Fe isotopes.