کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
6429406 | 1634762 | 2014 | 11 صفحه PDF | دانلود رایگان |
- The Amazon River shows homogeneous SPM δFe56 values during the year.
- SPM from the Amazon River has δFe56â¼0.07â° (mechanical weathering).
- The Negro River shows variable negative SPM δFe56 values during the year.
- The Negro River dissolved load shows heavy δFe56 values (chemical weathering).
- The SPM δFe56 delivered by the Amazon River to the Ocean â¼0.07â°.
Iron isotopic compositions (δFeIRMM-1456) of suspended particulate matter (SPM) from two major rivers in the Amazon Basin, the Amazon River itself (at the Ãbidos Station) and the Negro River (at the Serrinha Station), were investigated in the present study. The main objective was to search for temporal variations during their annual river cycles. δFeIRMM-1456 values for the Amazon River at Ãbidos range between 0.00 and +0.15â°, indistinguishable from the average continental crust value. In contrast, the iron isotopic compositions of the Negro River (Serrinha Station) SPM vary between â0.34 and â0.82â°, whereas the dissolved matter is isotopically heavier in this river. The lack of significant isotopic variations in the Amazon River indicates that one individual SPM subsurface sample is representative of the river during the whole annual river cycle, in opposition to results obtained for the Negro River. The data suggest that in organic-poor white water rivers, such as the Amazon, iron isotopic signatures of the suspended fraction reflect a detrital crustal component with little isotopic fractionation. On the other hand, in the organic-rich Negro River, which has tropical podzols as the main iron source, the iron redox cycling at the water-soil interface influences the iron isotopic composition.
Journal: Earth and Planetary Science Letters - Volume 394, 15 May 2014, Pages 168-178