Photochemistry of iron in aquatic environments.
Photochemistry of iron in aquatic environments.
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DOI：
10.1039/c9em00415g
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发表时间：
2020-01
期刊：
影响因子：
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通讯作者：
Ulf Lueder;B. Jørgensen;A. Kappler;C. Schmidt
中科院分区：
文献类型：
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作者：
Ulf Lueder;B. Jørgensen;A. Kappler;C. Schmidt
光能是水生系统中许多地球化学元素循环的驱动力。太阳光诱导的光化学还原三价铁（Fe（iii）photoreduction）的亚铁（Fe（ii））通过直接配体到金属的电荷转移或光化学产生的自由基可以溶解Feaq2+在水和沉积环境中的一个重要来源。活性氧（ROS）是由多种光依赖性反应形成的。这些ROS可以氧化Fe（ii）或还原Fe（iii），并且由于它们的高反应性，它们是影响许多其他生物地球化学循环的水生系统中的关键氧化剂。在pH值接近中性的好氧沃茨中，产生的Fe（ii）达到纳摩尔浓度并用作营养物，而在富含Fe（ii）的酸性沃茨、淡水和海洋沉积物中，光化学形成的Fe（ii）可以达到高达100微摩尔浓度并用作嗜酸好氧、微好氧、光养的额外电子供体，并且如果存在硝酸盐，硝酸盐还原Fe（ii）氧化细菌。因此，Fe（iii）光还原不仅控制着海洋初级生产力，而且对沿岸的淡水和海洋环境中Fe的循环有着巨大的影响。在这篇综述中，我们总结了涉及铁的光化学反应，讨论了ROS在铁循环中的作用，并强调了光还原过程在环境中的重要性。
Light energy is a driver for many biogeochemical element cycles in aquatic systems. The sunlight-induced photochemical reduction of ferric iron (Fe(iii) photoreduction) to ferrous iron (Fe(ii)) by either direct ligand-to-metal charge transfer or by photochemically produced radicals can be an important source of dissolved Feaq2+ in aqueous and sedimentary environments. Reactive oxygen species (ROS) are formed by a variety of light-dependent reactions. Those ROS can oxidize Fe(ii) or reduce Fe(iii), and due to their high reactivity they are key oxidants in aquatic systems where they influence many other biogeochemical cycles. In oxic waters with circumneutral pH, the produced Fe(ii) reaches nanomolar concentrations and serves as a nutrient, whereas in acidic waters, freshwater and marine sediments, which are rich in Fe(ii), the photochemically formed Fe(ii) can reach concentrations of up to 100 micromolar and be used as additional electron donor for acidophilic aerobic, microaerophilic, phototrophic and, if nitrate is present, for nitrate-reducing Fe(ii)-oxidizing bacteria. Therefore, Fe(iii) photoreduction may not only control the primary productivity in the oceans but has a tremendous impact on Fe cycling in the littoral zone of freshwater and marine environments. In this review, we summarize photochemical reactions involving Fe, discuss the role of ROS in Fe cycling, and highlight the importance of photoreductive processes in the environment.