Photochemical activation of chlorine by iron-oxide aerosol
Photochemical activation of chlorine by iron-oxide aerosol
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DOI：
10.1007/s10874-016-9336-6
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发表时间：
2017-06
影响因子：
2
通讯作者：
J. Wittmer;C. Zetzsch
中科院分区：
文献类型：
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作者：
J. Wittmer;C. Zetzsch
在聚四氟乙烯模拟室中的潮湿空气中，研究了人工海盐气溶胶液滴中溶解的铁和暴露于气态HCl的高度分散的氧化铁（Fe 2 O3）气溶胶颗粒（主要是赤铁矿，比表面积~150 m2 g −1）对氯的光化学活化。采用自由基时钟技术，我们量化了生产的气态原子氯（Cl）从辐照气溶胶。当盐气溶胶中含有Fe 2 O3在pH值为6时，没有观察到显着的Cl生产，即使溶解的铁是由“风化”（反复冻融5次）。将储备悬浮液的pH值调节至2.6、2.2和1.9，并平衡一周，得到了可定量的溶解铁（分别为0.03、0.2和0.6 mmol L−1）和气态Cl的产生速率分别为约1.6、6和8 × 1021 atoms cm− 2 h −1。在进一步的一系列实验中，纯Fe 2 O3气溶胶暴露于各种水平的气态氯化氢（HCl）。由此产生的氯的产生速率范围从8 × 1020 Cl atoms cm− 2 h −1（在~ 4ppb HCl下）到5 × 1022 Cl atoms cm− 2 h −1（在~350 ppb HCl下），并证实了HCl的吸收和转化为原子氯（在HCl到Cl的转化率为2- 5%，取决于相对湿度）。Fe 2 O3的实验表明，铁诱导的Cl形成可能是重要的高溶解性燃烧气溶胶颗粒在海洋环境中的气态HCl的存在下。
The photochemical activation of chlorine by dissolved iron in artificial sea-salt aerosol droplets and by highly dispersed iron oxide (Fe2O3) aerosol particles (mainly hematite, specific surface ~150 m2g−1) exposed to gaseous HCl, was investigated in humidified air in a Teflon simulation chamber. Employing the radical-clock technique, we quantified the production of gaseous atomic chlorine (Cl) from the irradiated aerosol. When the salt aerosol contained Fe2O3at pH 6, no significant Cl production was observed, even if the dissolution of iron was forced by “weathering” (repeatedly freezing and thawing for five times). Adjusting the pH in the stock suspension to 2.6, 2.2, and 1.9 and equilibrating for one week resulted in a quantifiable amount of dissolved iron (0.03, 0.2, and 0.6 mmol L−1, respectively) and in gaseous Cl production rates of ~1.6, 6, and 8 × 1021atoms cm−2h−1, respectively. In a further series of experiments, the pure Fe2O3aerosol was exposed to various levels of gaseous hydrogen chloride (HCl). The resulting Cl production rates ranged from 8 × 1020Cl atoms cm−2h−1(at ~4 ppb HCl) to 5 × 1022Cl atoms cm−2h−1(at ~350 ppb HCl) and confirmed the uptake and conversion of HCl to atomic Cl (at HCl to Cl conversion yields of 2–5 %, depending on the relative humidity). The Fe2O3experiments indicate that iron-induced Cl formation may be important for highly soluble combustion-aerosol particles in marine environments in the presence of gaseous HCl.