کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1263433 1496711 2009 11 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Impact of halides on the photobleaching of dissolved organic matter
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی (عمومی)
پیش نمایش صفحه اول مقاله
Impact of halides on the photobleaching of dissolved organic matter
چکیده انگلیسی

Understanding absorbance photobleaching of marine dissolved organic matter (DOM) is important because DOM chromophores impact oceanic primary productivity by affecting the depth of the photic zone, absorb UV radiation and affect ocean color used in remote sensing. However, the fundamental mechanisms which account for this bleaching are largely unknown. Controlled laboratory studies demonstrated that the presence of seawater concentrations of chloride and bromide ions enhanced absorbance photobleaching reaction rates by ~ 40%, regardless of DOM source or the presence or absence of carbonate ions. In contrast, halide ions generally did not affect fluorescence bleaching rates. Variations in ionic strength did not alter the enhancement in absorbance photobleaching by halide ions. Accordingly, the enhancement in absorbance photobleaching was specific to halide ions, rather than a generalized salinity effect. We confirmed the formation of hydroxyl radical (HO
• ) in illuminated samples, and its significant scavenging in the presence of halide salts. Gamma-radiolysis experiments and associated modeling indicated that a small component (~ 12%) of the photobleaching enhancement by halides was consistent with the hypothesis that halide scavenging of HO
• will form reactive halogen radicals that target electron-rich chromophores within DOM more selectively than HO
• . The mechanism responsible for the major component of absorbance photobleaching rate enhancement by halides remains unresolved.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Marine Chemistry - Volume 115, Issues 1–2, 20 June 2009, Pages 134–144
نویسندگان
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