Organics Substantially Reduce HO2 Uptake onto Aerosols Containing Transition Metal ions.
Organics Substantially Reduce HO2 Uptake onto Aerosols Containing Transition Metal ions.
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DOI：
10.1021/acs.jpca.5b06316
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发表时间：
2016-03
期刊：
影响因子：
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通讯作者：
P. Lakey;I. George;M. Baeza_Romero;L. Whalley;D. Heard
中科院分区：
文献类型：
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作者：
P. Lakey;I. George;M. Baeza_Romero;L. Whalley;D. Heard
在相对湿度为60±3%、温度为293±2K、氧气初始浓度为α1×10(9)分子cm(-3)的条件下，利用气溶胶流动管与灵敏的荧光气体膨胀氧检测系统相耦合，测得亚微米级铜(II)掺杂硫酸铵气溶胶的氧质量调节系数为∼=0.23±0.07。研究了在掺铜气溶胶中加入不同有机物种(丙二酸、柠檬酸、1，2-二氨基乙烷、酒石酸、乙二胺四乙酸和草酸)对HO2吸收系数γ的影响。当乙二胺四乙酸二钠与铜(II)离子按1：1摩尔比加入时，吸氧系数从质量容纳值稳定下降到γ=0.008±0.009；当草酸与铜(II)按10：1摩尔比加入气溶胶时，吸氧系数稳定地下降到γ=0.003±0.004。EDTA与铜(II)离子结合强烈，有可能使它们无法用于催化分解HO2，也可以作为表面活性剂或改变气溶胶的粘度。将草酸添加到气溶胶中可能会形成低挥发性的铜-草酸盐络合物，通过改变气溶胶的粘度或通过使气溶胶中的沉淀形成涂层来减少对HO2的吸收。在许多类型的大气气溶胶中，可能存在足够高的草酸盐与铜(II)离子的比例，从而降低了HO2的吸收系数。当其他有机物种(丙二酸、柠檬酸、1，2-二氨基乙烷和酒石酸)与铜(II)离子以10：1的摩尔比加入时，HO2吸收系数没有明显变化。
A HO2 mass accommodation coefficient of α = 0.23 ± 0.07 was measured onto submicron copper(II)-doped ammonium sulfate aerosols at a relative humidity of 60 ± 3%, at 293 ± 2 K and at an initial HO2 concentration of ∼ 1 × 10(9) molecules cm(-3) by using an aerosol flow tube coupled to a sensitive fluorescence assay by gas expansion (FAGE) HO2 detection system. The effect upon the HO2 uptake coefficient γ of adding different organic species (malonic acid, citric acid, 1,2-diaminoethane, tartronic acid, ethylenediaminetetraacetic acid (EDTA), and oxalic acid) into the copper(II)-doped aerosols was investigated. The HO2 uptake coefficient decreased steadily from the mass accommodation value to γ = 0.008 ± 0.009 when EDTA was added in a one-to-one molar ratio with the copper(II) ions, and to γ = 0.003 ± 0.004 when oxalic acid was added into the aerosol in a ten-to-one molar ratio with the copper(II). EDTA binds strongly to copper(II) ions, potentially making them unavailable for catalytic destruction of HO2, and could also be acting as a surfactant or changing the viscosity of the aerosol. The addition of oxalic acid to the aerosol potentially forms low-volatility copper-oxalate complexes that reduce the uptake of HO2 either by changing the viscosity of the aerosol or by causing precipitation out of the aerosol forming a coating. It is likely that there is a high enough oxalate to copper(II) ion ratio in many types of atmospheric aerosols to decrease the HO2 uptake coefficient. No observable change in the HO2 uptake coefficient was measured when the other organic species (malonic acid, citric acid, 1,2-diaminoethane, and tartronic acid) were added in a ten-to-one molar ratio with the copper(II) ions.