Influence of Fe(III) source, light quality, photon flux and presence of oxygen on photoreduction of Fe(III)-organic complexes - Implications for light-influenced coastal freshwater and marine sediments.
Influence of Fe(III) source, light quality, photon flux and presence of oxygen on photoreduction of Fe(III)-organic complexes - Implications for light-influenced coastal freshwater and marine sediments.
复制标题
Fe(III) 源、光质量、光子通量和氧的存在对 Fe(III)-有机络合物光还原的影响 - 对受光影响的沿海淡水和海洋沉积物的影响
DOI：
10.1016/j.scitotenv.2021.152767
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Kappler
中科院分区：
文献类型：
--
作者：
Lueder;Jørgensen;Maisch;Schmidt;Kappler
铁（III）的光还原是光照下水生和沉积环境中Fe（II）的重要来源。在有氧条件下，Fe（II）可以被氧气（O2）再氧化，形成活性O-物质，如过氧化氢（H2 O2），其进一步与Fe（II）反应，从而提高Fe（II）的氧化速率。然而，它是未知的水生沉积物如何参数的辐射波长，光子通量，起源的Fe（III）源和存在或不存在O2的影响程度的Fe（II）和H2 O2营业额。我们研究了这一点，使用不同的Fe（III）-有机配合物模拟沉积条件的批量实验。我们发现，波长<500 nm是必要的，以启动Fe（III）的光还原和光子通量，波长和身份的Fe（III）络合有机酸控制的Fe（III）的光还原动力学。光敏感的Fe（III）-有机络合物的形成不依赖于Fe（III）源是否是生物产生的，结晶不良的Fe（III）羟基氧化物或化学合成的水铁矿。氧化条件引起的化学再氧化的Fe（II）和积累的H2 O2。的光子通量，波长和可用性的Fe（III）络合有机分子是关键的并发Fe（III）的光还原和非生物Fe（II）氧化之间的平衡，甚至可能导致在微摩尔范围内的Fe（II）的稳态浓度。这些结果有助于理解和预测Fe（III）光还原动力学和原位形成的Fe（II）在好氧或缺氧，光照和有机丰富的环境。
Iron(III) photoreduction is an important source of Fe(II) in illuminated aquatic and sedimentary environments. Under oxic conditions, the Fe(II) can be re-oxidized by oxygen (O2) forming reactive O-species such as hydrogen peroxide (H2O2) which further react with Fe(II) thus enhancing Fe(II) oxidation rates. However, it is unknown by aquatic sediments how the parameters wavelength of radiation, photon flux, origin of Fe(III) source and presence or absence of O2influence the extent of Fe(II) and H2O2turnover. We studied this using batch experiments with different Fe(III)-organic complexes mimicking sedimentary conditions. We found that wavelengths <500 nm are necessary to initiate Fe(III) photoreduction and that the photon flux, wavelength and identity of Fe(III)-complexing organic acids control the kinetics of Fe(III) photoreduction. The formation of photo-susceptible Fe(III)-organic complexes did not depend on whether the Fe(III) source was biogenically produced, poorly-crystalline Fe(III) oxyhydroxides or chemically synthesized ferrihydrite. Oxic conditions caused chemical re-oxidation of Fe(II) and accumulation of H2O2. The photon flux, wavelength and availability of Fe(III)-complexing organic molecules are critical for the balance between concurrent Fe(III) photoreduction and abiotic Fe(II) oxidation and may even lead to a steady-state concentration of Fe(II) in the micromolar range. These results help understand and predict Fe(III) photoreduction dynamics and in-situ formation of Fe(II) in oxic or anoxic, illuminated and organic-rich environments.