Determination of calcium and sulfate species in aerosols associated with the conversion of its species through reaction processes in the atmosphere and its influence on cloud condensation nuclei activation
Determination of calcium and sulfate species in aerosols associated with the conversion of its species through reaction processes in the atmosphere and its influence on cloud condensation nuclei activation
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DOI：
10.1016/j.atmosenv.2019.117193
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发表时间：
2020-02
影响因子：
5
通讯作者：
C. Miyamoto;K. Sakata;Yoshiaki Yamakawa;Y. Takahashi
中科院分区：
文献类型：
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作者：
C. Miyamoto;K. Sakata;Yoshiaki Yamakawa;Y. Takahashi
采用X射线吸收近边结构(XANES)分析方法，对日本西南部东广岛地区采集的气溶胶中的钙(Ca)物种进行了测定，并对其粒度分布和季节变化进行了研究。钙K边X-射线光电子能谱分析表明，石膏(CaSO_4-⋅_2H_2O)和草酸钙(CaC_2O_4-⋅_2H_2O)是大气中矿物颗粒反应生成的主要钙物种。这些物种的吸湿性与方解石(CaCO3)相似，方解石是矿物颗粒中的一种原始钙物种。此外，高吸湿性的钙物种，如硝酸钙[Ca(NO3)2⋅4H2O]和氯化钙(CaCl2⋅2H2O)被认为是次要的钙物种。此外，矿物颗粒反应生成的CaSO_4-⋅_2H_2O抑制了硫酸盐吸湿气溶胶物种的形成，如硫酸铵[(NH_4)_2SO_4]，从而减少了云凝结核的数量。硫K边X-射线光电子能谱也证实了CaSO_4-⋅_2H_2O是粗颗粒中硫酸盐的主要形态。相比之下，高吸湿性硫酸盐(如(NH4)2SO4)是细颗粒物中的主要形态。此外，在采样期间，CaSO_4-⋅_2H_2O组分占总硫酸盐的比例增加，这受沙尘事件的影响。因此，反应减少了细颗粒中吸湿硫酸盐的量，在矿物粉尘存在的情况下，粗颗粒中生成了CaSO4⋅2H2O。虽然这些事实大多已被模拟和实验室研究所证实，但本研究表明，根据自然样品的X射线能谱分析气溶胶中钙和硫酸盐的形态，CaCO3反应生成CaSO4⋅2H2O将减少吸湿性硫酸盐气溶胶的数量。
Calcium (Ca) species in aerosols collected in Higashi–Hiroshima in southwestern Japan were determined by X-ray absorption near-edge structure (XANES) analysis, and their size distributions and seasonal variation were investigated. Calcium K-edge XANES results showed that gypsum (CaSO4⋅2H2O) and calcium oxalate (CaC2O4⋅2H2O) were the major Ca species that were formed by reactions of mineral particles in the atmosphere. These species exhibit similar hygroscopicity to that of calcite (CaCO3), which is an original Ca species in mineral particles. In addition, high hygroscopic Ca species, such as calcium nitrate [Ca(NO3)2⋅4H2O] and calcium chloride (CaCl2⋅2H2O) were considered minor Ca species. Moreover, the formation of CaSO4⋅2H2O by the reaction of mineral particles suppresses the formation of hygroscopic sulfate aerosol species, such as ammonium sulfate [(NH4)2SO4], reducing the number of cloud condensation nuclei (CCN). Sulfur K-edge XANES also confirmed that CaSO4⋅2H2O was a major species of sulfate in coarse particles. By contrast, high hygroscopic sulfate, such as (NH4)2SO4, was major species in fine particle. In addition, CaSO4⋅2H2O fraction to total sulfate increased during the sampling period, which was affected by a dust event. Consequently, the amount of hygroscopic sulfate in fine particles was decreased by the reaction, forming CaSO4⋅2H2O in coarse particles in the presence of mineral dust. Although these facts have been indicated mostly by modeling and laboratory studies, the present research suggested that the reaction of CaCO3to form CaSO4⋅2H2O will reduce the amount of hygroscopic sulfate aerosols based on natural sample measurement in terms of the speciation of Ca and sulfate in aerosols using XANES spectroscopy.