An experimental study of photo-oxidation of Fe(II): Implications for the formation of Fe(III) (hydro)oxides on early Mars and Earth
An experimental study of photo-oxidation of Fe(II): Implications for the formation of Fe(III) (hydro)oxides on early Mars and Earth
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Fe(II) 光氧化的实验研究：对早期火星和地球上 Fe(III)（氢）氧化物形成的影响
DOI：
10.1016/j.gca.2021.02.006
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发表时间：
2021
影响因子：
5
通讯作者：
S.
中科院分区：
文献类型：
--
作者：
Tabata;H.;Sekine;Y.;Kanzaki;Y.;Sugita;S.
水相 Fe(II)（Fe2+ 和 FeOH+）光氧化为 Fe(III) (Fe3+) 可能参与了早期火星和地球上氧化铁沉积物的形成。先前的研究报道了酸性条件（pH 0.4-3.0）下的光氧化反应速率（即量子产率，φ=氧化的亚铁离子数量除以亚铁离子吸收的光子数量）。然而，尚未在弱酸性至中性 pH 范围内使用化学光量测定法系统地研究量子产率，在早期火星和地球上，光氧化可能会发生在该范围内。我们根据测量的 Fe(II) 浓度和光子通量，报告了使用汞灯和氙灯（带或不带滤光片）在 0.5–7.6 pH 范围内对水性 Fe(II) 物质进行光氧化的量子产率。连续紫外光和可见光（>200nm，氙灯）下的量子产率随pH变化：φ=0.103（±0.005）+2.17（±0.27）×[H+]0.5（pH=3.0-7.0）。我们的量子产率比之前使用汞灯的研究报告的量子产率高出几倍，这表明量子产率与波长相关。在较高 pH 值 (7.1–7.6) 下，紫外截止波长≤300nm（过滤氙灯），Fe(II) 的光氧化归因于 FeOH+ 的氧化，量子产率为 0.08±0.01。根据这些量子产率，我们估计了火星早期盖尔湖和地球太古宙海洋中 Fe(III)（氢）氧化物的沉淀率。结果表明，假设水性 Fe(II) 通过地下水上涌供应到湖泊，光氧化可能解释了大风沉积物中 Fe(III)（氢）氧化物的含量。地球上太古代海洋中 Fe(II) 的光氧化可能比之前想象的要强烈数倍。
Photo-oxidation of aqueous Fe(II) (Fe2+and FeOH+) to Fe(III) (Fe3+) was likely involved in the formation of iron oxide deposits on early Mars and Earth. Previous studies have reported the photo-oxidation reaction rate (i.e., quantum yield,φ= the number of oxidized ferrous ions divided by the number of photons absorbed by ferrous ions) under acidic conditions (pH 0.4–3.0). However, the quantum yield has not been systematically investigated using chemical actinometry in the range of weakly acidic to neutral pH, where the photo-oxidation would have occurred on early Mars and Earth. We report quantum yields for the photo-oxidation of aqueous Fe(II) species over a pH range of 0.5–7.6 with Hg and Xe lamps (with and without optical filters) based on measured Fe(II) concentrations and photon fluxes. The quantum yield under continuous UV and visible light (>200 nm, Xe lamp) varies with pH:φ= 0.103 (±0.005) + 2.17 (±0.27) × [H+]0.5at pH = 3.0–7.0. Our quantum yield is a few times higher than those reported by the previous studies that used a Hg lamp, indicating the wavelength dependence of the quantum yield. At higher pH (7.1–7.6), with a UV cutoff at ≤ 300 nm (filtered Xe lamp), photo-oxidation of Fe(II) is attributed to oxidation of FeOH+, with a quantum yield of 0.08 ± 0.01. Based on these quantum yields, we estimated Fe(III) (hydro)oxide precipitation rates in the early Gale lakes on Mars, and in Archean oceans on Earth. Results suggest that photo-oxidation may account for the amounts of Fe(III) (hydro)oxides in Gale sediments, assuming aqueous Fe(II) was supplied to the lakes through upwelling groundwater. Photo-oxidation of Fe(II) in Archean oceans on Earth could have been several times more intense than previously thought.
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影响因子：
18.3
作者：
Tosca NJ;Ahmed IAM;Tutolo BM;Ashpitel A;Hurowitz JA
通讯作者：
Hurowitz JA
影响因子：
56.9
作者：
Eigenbrode, Jennifer L.;Summons, Roger E.;Coll, Patrice
通讯作者：
Coll, Patrice
火星表面部分氧化酸性硫酸盐水蒸发的实验限制
DOI：
--
发表时间：
2009
期刊：
影响因子：
--
作者：
N. Tosca;S. McLennan
通讯作者：
S. McLennan
影响因子：
18.3
作者：
Hurowitz, Joel A.;Fischer, WoodwardW.;Milliken, Ralph E.
通讯作者：
Milliken, Ralph E.
影响因子：
2.3
作者：
NIKOGOSYAN, DN;ORAEVSKY, AA;RUPASOV, VI
通讯作者：
RUPASOV, VI