Photochemical redox cycling of iron in coastal seawater
Photochemical redox cycling of iron in coastal seawater
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DOI：
10.1016/0304-4203(95)00027-o
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发表时间：
1995-08
期刊：
影响因子：
3
通讯作者：
William L. Miller;D. Whitney King;Jie Lin;D. R. Kester
中科院分区：
文献类型：
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作者：
William L. Miller;D. Whitney King;Jie Lin;D. R. Kester
在大量的实验室太阳模拟实验中，测量了还原铁Fe(II)和过氧化氢H_2O_2。在纳拉甘西特湾新收集的0.2μm过滤水的持续照射下，H_2O_2以30到59 NM h−1的速率以线性方式积累至少2小时。我们在本研究中对Fe(II)积累的测量提供了一些在受控实验室环境下在pH为8的天然海水中光化学铁还原的首次直接测量结果。在环境pH条件下，Fe(II)的峰值浓度为总铁浓度的4%~8%。在整个实验过程中，降低pH会导致Fe(II)浓度升高。测量了H_2O_2的积累量、已发表的氧化铁溶解产物和已发表的铁的氧化和被氧、过氧化氢和氧自由基还原的反应速率，建立了一个动力学模型，该模型解释了在我们的实验中观察到的Fe(II)浓度变化的一般大小和时间。我们的模型表明，辐照海水中测得的稳态Fe(II)浓度主要受pH相关的氧和过氧化氢氧化以及光化学产生的超氧化物对铁的氧化和还原控制。
Reduced iron, Fe(II), and hydrogen peroxide, H2O2, were measured in numerous laboratory solar simulation experiments. Under constant irradiation of freshly collected, 0.2 μm filtered water from Narragansett Bay (NBSW), H2O2accumulates in a linear fashion for at least 2 h at rates from 30 to 59 nM h−1. Our measurements of Fe(II) accumulation in this study provide some of the first direct measurements of photochemical iron reduction in natural seawater at pH 8 in a controlled laboratory setting. At ambient pH, the peak concentration of Fe(II) ranged from 4 to 8% of the total iron concentration. Lowering the pH resulted in increased Fe(II) concentrations over the entire course of the experiment. Measured H2O2accumulation, published iron oxide solubility products, and published reaction rates for iron oxidation and reduction by oxygen, hydrogen peroxide, and oxygen radicals were used to develop a kinetic model which accounts for the general magnitude and timing of Fe(II) concentration variations observed in our experiments. Our model shows that measured steady state Fe(II) concentrations in irradiated seawater are controlled largely by pH dependent oxidation by oxygen and hydrogen peroxide, and by both oxidation and reduction of iron by photochemically produced Superoxide.