Selenite and selenate in clouds at a high-altitude mountain location in Central Japan
Selenite and selenate in clouds at a high-altitude mountain location in Central Japan
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DOI：
10.1016/j.atmosres.2022.106253
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发表时间：
2022-05
影响因子：
5.5
通讯作者：
M. Kagawa;N. Katsuta;Y. Ishizaka
中科院分区：
文献类型：
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作者：
M. Kagawa;N. Katsuta;Y. Ishizaka
大气是硒（Se）的临时储存库。了解硒在初级排放中的化学反应和形态是至关重要的，因为大气沉降是陆地（农业）系统硒污染和微量营养素的重要来源。在这项研究中，亚硒酸盐和硒酸盐的浓度在酸性云水（pH 4.3平均），包括非降水和降水云，分析了在山顶附近的网站。Norikura（海拔2770米），日本中部。云水中的可溶性硒与非海盐硫酸盐中的可溶性硒呈正相关，表明硒以硫酸铵的形式存在。硫酸铵产生于日本西南部和中国的工业和城市地区的化石燃料燃烧。在云水中的硒和硒酸盐的浓度逐渐下降，随着酸度（pH值）的上升，在大致相同的比例。亚硒酸盐和硒酸盐的共存可能表明HSeO 3 −-SeO 42 −对的氧化还原平衡。在降水云水中，亚硒酸盐是所有云事件中的主要组分。这可能是由于清除当地的燃煤气溶胶从日本西南部的雨滴（冲洗）。的硒/硒酸盐比的云以及降水云不相关的气态O3浓度，并保持稳定，在整个白天和黑夜。此外，模拟云水条件的硒-过氧化氢（H2 O2）溶液的实验室实验表明，亚硒酸（HSeO 3 −）不能被H2 O2氧化。观测和实验结果表明，酸性云中Se的氧化态不是由可能的SO2氧化剂如H2 O2和O3氧化引起的。
The atmosphere is a temporal reservoir of selenium (Se). Understanding the chemical reactions and speciation of Se in primary emissions is crucial because atmospheric deposition is an important source of both Se contamination and micronutrients for terrestrial (agricultural) systems. In this study, the concentrations of selenite and selenate in acid cloud water (pH 4.3 average), including non-precipitating and precipitating clouds, were analyzed at a site near the summit of Mt. Norikura (2770 m a.s.l.), central Japan. The soluble Se in cloud water has a positive correlation with that of non-sea-salt sulfate, implying that the Se was incorporated in ammonium sulfate. The ammonium sulfate was generated from fossil fuel combustions in industrial and urban areas of southwest Japan and China. The concentrations of selenite and selenate in cloud water gradually decreased with a rise in acidity (pH) in approximately the same proportion. The coexistence of selenite and selenate perhaps indicates an oxidation-reduction equilibrium for the HSeO3−–SeO42−couple. For the precipitating cloud water, the selenite was the dominant species in all cloud events. This may be attributed to scavenging of local coal-combustion aerosols from southwest Japan by the rain droplets (washout). The selenite/selenate ratios of clouds as well as precipitating clouds were not correlated with gaseous O3concentrations and remained stable throughout both day and night. In addition, laboratory experiments with Se–hydrogen peroxide (H2O2) solutions mimicking the cloud water conditions indicated that selenious acids (HSeO3−) cannot be oxidized with H2O2. The observational and experimental results suggest that the Se oxidation states in acid clouds are not caused by oxidation by the possible oxidants for SO2such as H2O2and O3.