Speciation and isotopic analysis of zinc in size-fractionated aerosol samples related to its source and chemical processes
Speciation and isotopic analysis of zinc in size-fractionated aerosol samples related to its source and chemical processes
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DOI：
10.1016/j.atmosenv.2022.119504
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发表时间：
2022-11
影响因子：
5
通讯作者：
Sachika Natori;M. Fujiwara;Minako Kurisu;M. Tanimizu;T. Iizuka;Y. Takahashi
中科院分区：
文献类型：
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作者：
Sachika Natori;M. Fujiwara;Minako Kurisu;M. Tanimizu;T. Iizuka;Y. Takahashi
气溶胶中的锌（Zn）具有重要的生物活性，从环保措施的角度引起了人们的关注。由于锌具有高挥发性和水溶性，人类活动很容易将其释放到大气中，并供应给天然水。为了探索大气气溶胶中Zn的来源和形成过程，研究Zn在粒径分馏气溶胶中的同位素（= δ66Zn）和形态信息至关重要。我们对2002年在筑波、千叶和高速公路隧道（广岛安山隧道）采集的样品进行了轻δ66Zn（例如δ66ZnIRMM= - 1.32‰，本研究使用IRMM-3702进行了归一化）测量，主要针对0.65 ~ 4.7 μm的颗粒进行了测量，但2011年和2016年采集的样品δ66ZnIRMMin的粒径增加到- 0.8‰以上。基于x射线吸收近边结构（XANES）和扩展x射线吸收精细结构（EXAFS）光谱对气溶胶中Zn的种类进行了估算，结果表明：(1)草酸锌和硫酸盐锌以及(2)氧化锌、硫化锌和碳酸盐锌分别是细颗粒和粗颗粒中的主要Zn种类。其中氯化锌主要分布在中粒径范围（2.1 ~ 4.7 μm），与轻δ66Zn的粒径范围相对应，表明轻δ66Zn是由人工燃烧过程中释放的氯化锌引起的。假设气溶胶中锌的起源有三个端元；(A)轮胎和刹车磨损和道路灰尘，(B)工业排放，(C)车辆尾气。通过对不同粒径Zn的大气浓度、形态和同位素组成的综合分析，认为它们的形成机制与汽化和混合过程有关。这些变化趋势可以用不同物种的δ66Zn值来解释：组分(A)主要由氧化锌和硫化锌组成，δ66Zn相对较重；组分(B)以液滴形式次生形成的氯化锌和硫酸盐，δ66Zn在所有组分中最轻；组分(C)草酸锌，δ66Zn接近0‰，是由汽车发动机完全燃烧排放的。通过同时应用粒径分馏气溶胶中Zn的物种形成和同位素分析获得的物种特异性Zn同位素数据，为气溶胶中Zn物种形成的初始生成和二次过程提供了新的信息。
Zinc (Zn) in aerosols plays important roles for biological activity and attracts public attention from the perspective of environmental measures. Because of its high volatility and water solubility, Zn is readily released into the atmosphere by human activities and supplied to natural water. To explore the origin and formation process of Zn in atmospheric aerosols, it is important to investigate isotopic (= δ66Zn) and speciation information of Zn in size-fractioned aerosols. We measured light δ66Zn (e.g., δ66ZnIRMM= −1.32‰ as the lowest value; IRMM-3702 is used for the normalization in this study) mainly for the particles ranging from 0.65 to 4.7 μm for the samples collected at Tsukuba, Chiba, and a motorway tunnel (Yasumiyama Tunnel in Hiroshima) in particular for the samples collected in 2002, but δ66ZnIRMMin the particle sizes increased above −0.8‰ for the samples collected in 2011 and 2016. Zn species in aerosols were estimated based on X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy, suggesting that (i) Zn oxalate and sulfate and (ii) Zn oxide, sulfide, and carbonate are main Zn species in fine and coarse particles, respectively. In particular, Zn chloride was found mainly in the middle particle size range (2.1–4.7 μm), which corresponds to the range with light δ66Zn, suggesting that the light δ66Zn was caused by emission of Zn chloride during artificial combustion processes in accordance with other studies. The origins of Zn in aerosols are assumed to have three endmembers; (A) tire and brake wears and road dust, (B) industrial emissions, and (C) vehicular exhaust. Their formation mechanisms are related to vaporization and mixing processes based on the results of combined analysis of atmospheric concentration, speciation, and isotopic composition of Zn with different particle sizes. These trends could be successfully interpreted by species-specific δ66Zn values: component (A) consisting mainly of Zn oxide and sulfide with relatively heavier δ66Zn, component (B) Zn chloride and sulfate secondarily formed in the droplet mode having lightest δ66Zn among all the species, and (C) Zn oxalate with δ66Zn closer to 0‰ due to its emission by the complete combustion in vehicle engines. Species-specific Zn isotope data obtained by the simultaneous application of speciation and isotopic analyses of Zn in size-fractionated aerosols complementary provide novel information on the initial generation and secondary processes for the formation of Zn species in the aerosols.