کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
6428238 | 1634732 | 2015 | 11 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Transport and reaction of iron and iron stable isotopes in glacial meltwaters on Svalbard near Kongsfjorden: From rivers to estuary to ocean
دانلود مقاله + سفارش ترجمه
دانلود مقاله ISI انگلیسی
رایگان برای ایرانیان
کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
علوم زمین و سیاره ای (عمومی)
پیش نمایش صفحه اول مقاله
چکیده انگلیسی
Glacial meltwater has been suggested as a significant source of potentially bioavailable iron to the oceans. However, the supply of dissolved iron (dFe) in glacial meltwaters is poorly constrained as few sites have been studied, and because the chemical processing of Fe during transport from glaciers to the adjacent coastal ocean is not well understood. In order to better constrain glacial fluxes of dFe to the ocean, iron concentrations, iron stable isotopes (δ56Fe), and other supporting chemical and physical measurements were made along a â¼4 km long glacial meltwater river on Svalbard and in estuarine waters that it flows into. Dissolved iron concentrations in the Bayelva River decreased from a maximum of 734 nM near the glacier to an average value of 116 nM near the mouth of the river. Measurements in the Kongsfjorden estuary suggest that 3 to 10 nM of dFe from the Bayelva River is stabilized in glacial waters by the time it mixes into the ocean. Incubation of Bayelva River waters over two weeks in both the light and dark show similar results, with the majority of dFe being quickly precipitated and 4 to 7 nM Fe stabilized in the dissolved phase. Evidence suggests that Fe is most likely lost from the dissolved phase by aggregation and adsorption of nanoparticulate and colloidal Fe to particles. Dissolved δ56Fe was between â0.11â° and +0.09â° for all river samples and did not vary systematically with dFe concentrations. We infer that the Fe is lost from the dissolved phase by a process that fractionates Fe isotopes by less than 0.05â°, indicating that the Fe bonding environment does not change during precipitation. This is consistent with DOC loss that is much faster than predicted photo-oxidation rates, suggesting that DOC is also lost through adsorption and precipitation. Dissolved Fe concentrations in the Bayelva River (15-734 nM), and Fe concentrations which are stabilized in the dissolved phase (4-7 nM) are much lower than some previous estimates of Fe in glacial meltwaters, with roughly 80% of dFe lost during transit in the Bayelva River and roughly 90% of the remaining dFe lost in the estuary. This may mean that glaciers are a less significant source of dissolved Fe to the global oceans than has been previously hypothesized, that cold base glaciers of the type studied here do not contribute significantly to the dissolved Fe flux, or that the flux of reactive particulate Fe to the oceans is more important than the dissolved flux. In Arctic regions with similar proglacial environments, bedrock composition, weathering intensity, and as precipitation of colloidal and nanoparticulate Fe may all play an important role in regulating the glacial meltwater iron flux to the ocean.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Earth and Planetary Science Letters - Volume 424, 15 August 2015, Pages 201-211
Journal: Earth and Planetary Science Letters - Volume 424, 15 August 2015, Pages 201-211
نویسندگان
Ruifeng Zhang, Seth G. John, Jing Zhang, Jingling Ren, Ying Wu, Zhuoyi Zhu, Sumei Liu, Xunchi Zhu, Chris M. Marsay, Fred Wenger,