کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4698539 1637568 2015 10 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Effects of ultraviolet radiation on mercury isotope fractionation during photo-reduction for inorganic and organic mercury species
ترجمه فارسی عنوان
اثرات تابش اشعه ماوراء بنفش بر کسر کردن ایزوتوپ جیوه در هنگام کاهش عکس برای گونه های جیوه معدنی و آلی
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات ژئوشیمی و پترولوژی
چکیده انگلیسی


• We examined how energy of radiation affected Hg mass-independent isotope fractionation (MIF) during photo-reduction.
• There is a clear relationship between Hg MIF and the energy of radiation during photo-reduction.
• Hg MIF during Hg2 + photo-reduction is significantly influenced by both UVB and UVA radiation.
• During methylmercury photodemethylation, UVB radiation is mostly responsible for the Hg MIF.
• There was no correlation between the observed mass-independent fractionation and total photo-reduction.

Photo-reduction of mercury (Hg) is an important mechanism for removal of both Hg2+ species and monomethylmercury (MMHg) from surface waters. Large mass independent fractionation (MIF) signatures of Hg isotopes preserved in natural samples are thought to reflect MIF produced during aqueous photo-reduction by the magnetic isotope effect (MIE). Recently, Hg MIF signatures in natural samples are being used to quantify photochemical reduction in aquatic systems. However, the fractionation factors used are from laboratory experiments that did not investigate many of the environmental parameters that may affect MIF during photo-reduction. In this study, the effects of different regions of the solar spectrum on the expression of MIF caused by the MIE during Hg2+ and MMHg photo-reduction were investigated to assess how the type of radiation affects the extent and signature of MIF. Photo-reduction in the presence of DOM was carried out through exposure to the full natural solar spectrum unfiltered, with the ultraviolet B (UVB; 290–320 nm) portion removed and with both the UVB and the ultraviolet A (UVA; 320–400 nm) removed. There is a clear relationship between the expression and magnitude of MIF and the energy of incident radiation for both Hg2+ and MMHg photo-reduction. The experiments indicate that MIF produced during photo-reduction of Hg2+ is significantly influenced by both UVB and UVA radiation. For MMHg photodemethylation, however, UVB radiation is mostly responsible for the MIF with minor contributions from UVA. Overall, there is a lack of correlation between the observed MIF and total photo-reduction in the experiments conducted in this study, which indicates that indirect and other non-MIF producing pathways of photo-reduction are the dominant pathways by which Hg species are being photo-reduced. Extrapolating these experimental results to natural systems is difficult as the experiments were not performed at realistic Hg/DOM ratios and the distribution of ligands that Hg is bound to in the experiments likely differs from natural systems. However, the strong relationship between MIF and energy of incident radiation in this study supports Hg MIF signatures as promising tools for helping to quantify photochemical cycling of mercury, but this study also highlights the need to understand the link between MIF and total photo-reduction before this tool can be fully utilized.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Chemical Geology - Volume 405, 5 June 2015, Pages 102–111
نویسندگان
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