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首页> 外文期刊>Atmospheric chemistry and physics >Iron dissolution kinetics of mineral dust at low pH during simulated atmospheric processing
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Iron dissolution kinetics of mineral dust at low pH during simulated atmospheric processing

机译：模拟大气处理过程中低pH下矿物粉尘的铁溶解动力学

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We investigated the iron (Fe) dissolution kinetics of African (Tibesti) andAsian (Beijing) dust samples at acidic pH with the aim of reproducing thelow pH conditions in atmospheric aerosols. The Beijing dust and three sizefractions of the Tibesti dust (<20 μm: PM20; <10 μm:PM10; and <2.5 μm: PM2.5) were dissolved at pH 1, 2 and/or3 for up to 1000 h. In the first 10 min, all dust samples underwent anextremely fast Fe solubilisation. Subsequently, the Fe dissolution proceededat a much slower rate before reaching a stable dissolution plateau. Thetime-dependant Fe dissolution datasets were best described by a modelcomprising three acid-extractable Fe pools each dissolving according tofirst-order kinetics. The dissolution rate constant k (h−1) of each poolwas independent of the source (Saharan or Asian) and the size (PM20,PM10 or PM2.5) of the dust but highly dependent on pH. The"fast" Fe pool had a k (25 h?1 at pH = 1) of a similar magnitude to"dry" ferrihydrite nanoparticles and/or poorly crystalline Fe(III)oxyhydroxide, while the "intermediate" and "slow" Fe pools had k valuesrespectively 50–60 times and 3000–4000 times smaller than the "fast" pool.The "slow" Fe pool was likely to consist of both crystalline Fe oxidephases (i.e., goethite and/or hematite) and Fe contained in the clayminerals. The initial mass of the "fast", "intermediate" and "slow" Fepools represented respectively about 0.5–2%, 1–3% and 15–40% ofthe total Fe in the dust samples. Furthermore, we showed that in systemswith low dust/liquid ratios, Fe can be dissolved from all three pools,whereas at high dust/liquid ratios (e.g., in aerosols), sufficient Fe may besolubilised from the "fast" phase to dominate the Fe dissolved and tosuppress the dissolution of Fe from the other Fe pools. These datademonstrated that dust/liquid ratio and pH are fundamental parameterscontrolling Fe dissolution kinetics in the dust. In order to reduce errorsin atmospheric and climate models, these fundamental controlling factorsneed to be included.
机译：我们研究了非洲（Tibesti）和亚洲（北京）粉尘样品在酸性pH下的铁（Fe）溶解动力学，目的是再现大气气溶胶中的低pH条件。北京尘埃和Tibesti尘埃的三个尺寸分数（<20μm：PM 20 ; <10μm：PM 10 ; <2.5μm：PM 2.5 < ）在pH 1、2和/或3下溶解达1000小时。在最初的10分钟内，所有粉尘样品都经历了极快的铁溶解。随后，Fe的溶解速度要慢得多，直到达到稳定的溶解平台。随时间变化的铁溶出数据集最好用一个模型描述，该模型包含三个可酸萃取的铁矿，每个铁矿均根据一级动力学溶解。每个池的溶出速率常数 k （h −1 ）与来源（撒哈拉或亚洲）和大小（PM 20 ）无关，灰尘的PM 10 或PM 2.5 ），但高度依赖于pH。 “快速”铁池的 k （在pH = 1时为25 h ？1 ）的大小与“干燥”亚铁酸盐纳米颗粒和/或结晶度较差的Fe（ III）羟基氧化铁，而“中级”和“慢速” Fe池的 k 值分别比“快速”池小50–60倍和3000–4000倍。“慢速” Fe池很可能既包含结晶的Fe氧化物相（即针铁矿和/或赤铁矿），也包含在粘土矿物中。 “快”，“中”和“慢” Fepool的初始质量分别约占粉尘样品中总铁的0.5–2％，1–3％和15–40％。此外，我们表明，在粉尘/液体比率低的系统中，Fe可以从所有三个池中溶解，而在粉尘/液体比率高的情况下（例如，在气溶胶中），可以从“快”相中溶解出足够的Fe以占主导地位。溶解并抑制其他铁库中铁的溶解。这些数据证明粉尘/液体比和pH是控制Fe在粉尘中溶解动力学的基本参数。为了减少大气和气候模型中的误差，这些基本控制因素需要包括在内。

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