Study of Iron Speciation and Isotopic Fractionation in the Waters From the Amazon River and Its Tributaries
Year: 2013
Type: preprint
Abstract: This work aimed to evaluate the influence of Fe speciation on its isotopic composition in waters with contrasted chemical features. Iron isotope ratios were determined using a Thermo Finnigan Neptune MC-ICP-MS (Multicollector - Inductively Coupled Plasma - Mass Spectrometer) with medium or high resolution entry slits, according to the Fe concentration of the samples and the sensitivity of the equipment. The present study shows, for the first time, that Fe adsorption on the phytoplankton cell walls can cause significant isotopic fractionation with preferential accumulation of heavy isotopes on the solid interface. The observed Fe isotopic fractionation (57Fecell-solution) was ~2.5‰ for initial solutions containing aqueous Fe2+ species, and ~ 1.0 ‰ for initial solutions containing aqueous Fe3+ species. This work also shows that bulk water sample storage can cause variations in the dissolved Fe isotopic composition, especially in waters with high concentrations of organic matter stored at room temperature. The Fe isotopic composition of the different pore-sized fractions from the Amazon Basin waters provided precise information about the sources and biogeochemical processes occurring in the upland soils and proved to be good proxies of the mechanisms involving Fe loss and transfer in the mixing zone. Considering that the Fe isotopes composition carries the records of the main sources and biogeochemical processes in soils, it can also be a promising tool to investigate the effects of land use modification and climate changes on continental weathering.
Author: Daniel Santos Mulholland
Language: English
Subfield: Geochemistry and Petrology
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2884738832