化学
溶解有机碳
过氧化氢
激进的
腐植酸
单线态氧
砷
光化学
羟基自由基
环境化学
氧气
无机化学
有机化学
肥料
作者
Johanna Buschmann,Silvio Canonica,Ursula Lindauer,Stephan J. Hug,Laura Sigg
摘要
The fate of arsenic in aquatic systems is influenced by dissolved natural organic matter (DOM). Using UV-A and visible light from a medium-pressure mercury lamp, the photosensitized oxidation of As(III) to As(V) in the presence of Suwannee River humic acid was investigated. Pseudo-first-order kinetics was observed. For 5 mg L-1 of dissolved organic carbon (DOC) and 1.85 mEinstein m-2 s-1 UV-A fluence rate, the rate coefficient k°exp was 21.2 ± 3.2 10-5 s-1, corresponding to a half-life <1 h. Rates increased linearly with DOC and they increased by a factor of 10 from pH 4 to 8. Based on experiments with radical scavengers, heavy water, and surrogates for DOM, excited triplet states and/or phenoxyl radicals seem to be important photooxidants in this system (rather than singlet oxygen, hydrogen peroxide, hydroxyl radicals, and superoxide). Photoirradiation of natural samples from freshwater lakes, rivers, and rice field water (Bangladesh) showed similar photoinduced oxidation rates based on DOC. Fe(III) (as polynuclear Fe(III)−(hydr)oxo complexes or Fe(III)−DOC complexes) accelerates the rate of photoinduced As(III) oxidation in the presence of DOC by a factor of 1.5−2.
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