Investigation of Humic Substance Photosensitized Reactions via Carbon and Hydrogen Isotope Fractionation

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• 作者：Ning Zhang ; Janine Schindelka ; Hartmut Herrmann ; Christian George ; M貌nica Rosell ; Sara Herrero-Mart铆n ; Petr Kl谩n ; Hans H. Richnow
• 刊名：Environmental Science & Technology
• 出版年：2015
• 出版时间：January 6, 2015
• 年：2015
• 卷：49
• 期：1
• 页码：233-242
• 全文大小：416K
• ISSN：1520-5851

文摘

Humic substances (HS) acting as photosensitizers can generate a variety of reactive species, such as OH radicals and excited triplet states (³HS*), promoting the degradation of organic compounds. Here, we apply compound-specific stable isotope analysis (CSIA) to characterize photosensitized mechanisms employing fuel oxygenates, such as methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE), as probes. In oxygenated aqueous media, 螞 (螖未²H/螖未¹³C) values of 23 卤 3 and 21 卤 3 for ETBE obtained by photosensitization by Pahokee Peat Humic Acid (PPHA) and Suwannee River Fulvic Acid (SRFA), respectively, were in the range typical for H-abstraction by OH radicals generated by photolysis of H₂O₂ (螞 = 24 卤 2). However, ³HS* may become a predominant reactive species upon the quenching of OH radicals (螞 = 14 卤 1), and this process can also play a key role in the degradation of ETBE by PPHA photosensitization in deoxygenated media (螞 = 11 卤 1). This is in agreement with a model photosensitization by rose bengal (RB^{2鈥?/sup>) in deoxygenated aqueous solutions resulting in one-electron oxidation of ETBE (螞 = 14 卤 1). Our results demonstrate that the use of CSIA could open new avenues for the assessment of photosensitization pathways.}