Iron dissolution kinetics of mineral dust at low pH during simulated atmospheric processing
Iron dissolution kinetics of mineral dust at low pH during simulated atmospheric processing
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DOI：
10.5194/acp-11-995-2011
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发表时间：
2010-11
影响因子：
6.3
通讯作者：
Zongbo Shi;S. Bonneville;M. Krom;K. Carslaw;T. Jickells;A. Baker;L. Benning
中科院分区：
文献类型：
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作者：
Zongbo Shi;S. Bonneville;M. Krom;K. Carslaw;T. Jickells;A. Baker;L. Benning
摘要。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。在pH值为1、2和/或3的条件下，将北京沙尘和Tibesti沙尘的3个粒径组分（20、10和2.5）溶解1000小时。在前10分钟，所有沙尘样品都经历了极快的铁溶解。随后，铁的溶解以较慢的速度进行，然后达到稳定的溶解平台。随时间变化的铁溶解数据集最好地描述了一个由三个酸萃取铁池组成的模型，每个铁池根据一级动力学溶解。溶解速率常数k (h−1)每个池是独立于源(撒哈拉或亚洲)和大小(10点20点或下午2.5)的尘埃但高度依赖博士“快速”铁池有k(25在pH = 1 h−1)类似规模的“干”水铁矿纳米颗粒和/或缺乏晶体铁(III)氢氧化物,而“中间”和“慢”铁池k值分别为50 - 60和3000 - 4000乘以小于“快速”池。“慢”铁池可能由结晶铁氧化物相（即针铁矿和/或赤铁矿）和粘土矿物中含有的铁组成。“快”、“中”和“慢”铁池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，在低尘液比的系统中，铁可以从所有三个池中溶解，而在高尘液比的系统中（例如，在气溶胶中），足够的铁可以从“快速”相中溶解，以主导铁的溶解，并抑制其他铁池中铁的溶解。这些数据表明，尘液比和pH是控制铁在粉尘中溶解动力学的基本参数。为了减少大气和气候模式的误差，需要包括这些基本的控制因素。
Abstract. We investigated the iron (Fe) dissolution kinetics of African (Tibesti) and Asian (Beijing) dust samples at acidic pH with the aim of reproducing the low pH conditions in atmospheric aerosols. The Beijing dust and three size fractions of the Tibesti dust ( 20 ; 10 ; and 2.5 ) were dissolved at pH 1, 2 and/or 3 for up to 1000 h. In the first 10 min, all dust samples underwent an extremely fast Fe solubilisation. Subsequently, the Fe dissolution proceeded at a much slower rate before reaching a stable dissolution plateau. The time-dependant Fe dissolution datasets were best described by a model comprising three acid-extractable Fe pools each dissolving according to first-order kinetics. The dissolution rate constant k (h −1 ) of each pool was independent of the source (Saharan or Asian) and the size (PM 20 , PM 10 or PM 2.5 ) 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 values respectively 50–60 times and 3000–4000 times smaller than the "fast" pool. The "slow" Fe pool was likely to consist of both crystalline Fe oxide phases (i.e., goethite and/or hematite) and Fe contained in the clay minerals. The initial mass of the "fast", "intermediate" and "slow" Fe pools represented respectively about 0.5–2%, 1–3% and 15–40% of the total Fe in the dust samples. Furthermore, we showed that in systems with 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 be solubilised from the "fast" phase to dominate the Fe dissolved and to suppress the dissolution of Fe from the other Fe pools. These data demonstrated that dust/liquid ratio and pH are fundamental parameters controlling Fe dissolution kinetics in the dust. In order to reduce errors in atmospheric and climate models, these fundamental controlling factors need to be included.