Vapor generation of mercury and methylmercury in aqueous microdroplets produced by pneumatic nebulization
Vapor generation of mercury and methylmercury in aqueous microdroplets produced by pneumatic nebulization
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气动雾化产生的水微滴中汞和甲基汞的蒸气生成
DOI：
10.1039/d2ja00137c
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发表时间：
2022
影响因子：
3.4
通讯作者：
Zhang Jing
中科院分区：
文献类型：
--
作者：
He Qian;Zhang Ningxin;Qiao Yifan;Li Chenchen;Zhang Jing
在原子光谱法中，气动雾化（PN）通常用于从散装溶液中引入微液滴（或气溶胶）。本研究发现，在不添加任何氧化还原剂、电或辐射的情况下，由汞离子（Hg2+）和甲基汞离子（MeHg+）生成挥发性单质汞（Hg0）的水蒸气生成过程可以在PN制备的水微滴中自发发生。MeHg+的降解可能是由羟基自由基（OH˙）引起的，Hg2+的还原可能是由OH−释放的电子引起的，它们都是在PN制备的微滴的水气界面上自发形成的。采用冷蒸汽原子荧光光谱法（CVAFS）检测Hg2+，详细评价了PN参数（雾化气体压力、微滴直径、载体溶液流速和溶液pH）对Hg2+和MeHg+蒸汽生成效率的影响。微滴对Hg2+的生蒸气效率约为37.2%。在10 μg L−1浓度下测定的Hg2+和MeHg+的相对标准偏差（RSD）分别为2.5%和3.4%。Hg2+和MeHg+的检出限（lod）分别为0.09 μg L−1和0.43 μg L−1。与其他蒸汽生成技术相比，微液滴诱导蒸汽生成技术为低能源成本的绿色化学提供了创新机会。此外，水微滴可能为云中的Hg2+还原参与全球大气汞循环提供了新的途径。
Pneumatic nebulization (PN) is commonly used for microdroplet (or aerosol) introduction from bulk solution in atomic spectrometry. Here, we found that the vapor generation process of mercury ion (Hg2+) and methylmercury ion (MeHg+) to volatile elemental mercury (Hg0) could spontaneously occur in aqueous microdroplets produced by PN without any added redox agent, electricity or radiation. The MeHg+ degradation might be caused by a hydroxyl radical (OH˙) and the Hg2+ reduction might be caused by the electron released from OH−, which were all formed spontaneously at the water–air interface of microdroplets produced by PN. With cold vapor atomic fluorescence spectrometry (CVAFS) as the detector for Hg0, the parameters in PN (including nebulizing gas pressure, microdroplet diameter, carrier solution flow rate, and solution pH) on the Hg2+ and MeHg+ vapor generation efficiencies were evaluated in detail. The vapor generation efficiency of Hg2+ by microdroplets was about 37.2%. The relative standard deviation (RSD) of Hg2+ and MeHg+ determined at 10 μg L−1 were 2.5% and 3.4%, respectively. The detection limits (LODs) of Hg2+ and MeHg+ were 0.09 μg L−1 and 0.43 μg L−1, respectively. Compared with other vapor generation technologies, microdroplets induced vapor generation technology provides an innovative opportunity for green chemistry with low energy cost. Moreover, aqueous microdroplets may have provided a new route for Hg2+ reduction in clouds to participate in the global atmospheric mercury cycling.