the observed isotopically very light aqueous iron and the variation in the 56Fe/54Fe ratio are interpreted as reflecting redox cycling, with progressive isotopic fractionation during Fe (II) adsorption onto newly formed ferric iron oxyhydroxides which precipitate to form immobile particles in the sediments; The iron isotopic systematics have been applied to study the interconversion between soluble reduced species and insoluble oxyhydroxides due to redox boundaries in groundwaters from the Grado-Marano lagoon, northern Adriatic Sea (Italy), an area characterized by ferrous iron-rich coastal aquifers. Groundwaters for isotopic analysis were flushed through piezometers, filtered and immediately acidified to prevent the effects of oxidation reactions. The delta56 Fe value ranges between -7.70±0.38 and +0.50±0.28, showing a progressive increase approaching the shoreline. Nevertheless, the Fe isotopic fractionation does not correlate with the chloride content, as would be expected, if the seawater-groundwater interface beneath the coastline played a major role in the iron oxidation rate. A trend of decreasing delta56Fe with decreasing Fe (II)(aq) activity is observed, and the water sample with the higher iron concentration among those studied (212 µM/L) shows the delta 56Fe value approaching the iron isotopic composition reported for rocks and soils. A lithogenic source for iron is suggested
Iron isotope-fractionation in coastal aquifers from the Grado-Marano lagoon, Adriatic Sea (Italy): preliminary results / Castorina, Francesca; A., Lutman; E., Pezzetta; R., Petrini. - In: GEOCHIMICA ET COSMOCHIMICA ACTA. - ISSN 0016-7037. - STAMPA. - 74:1(2010), pp. A149-A149. (Intervento presentato al convegno Conference on Goldschmidt 2010 - Earth, Energy, and the Environment tenutosi a Knoxville, TN nel JUN 13-18, 2010).
Iron isotope-fractionation in coastal aquifers from the Grado-Marano lagoon, Adriatic Sea (Italy): preliminary results
CASTORINA, Francesca;
2010
Abstract
the observed isotopically very light aqueous iron and the variation in the 56Fe/54Fe ratio are interpreted as reflecting redox cycling, with progressive isotopic fractionation during Fe (II) adsorption onto newly formed ferric iron oxyhydroxides which precipitate to form immobile particles in the sediments; The iron isotopic systematics have been applied to study the interconversion between soluble reduced species and insoluble oxyhydroxides due to redox boundaries in groundwaters from the Grado-Marano lagoon, northern Adriatic Sea (Italy), an area characterized by ferrous iron-rich coastal aquifers. Groundwaters for isotopic analysis were flushed through piezometers, filtered and immediately acidified to prevent the effects of oxidation reactions. The delta56 Fe value ranges between -7.70±0.38 and +0.50±0.28, showing a progressive increase approaching the shoreline. Nevertheless, the Fe isotopic fractionation does not correlate with the chloride content, as would be expected, if the seawater-groundwater interface beneath the coastline played a major role in the iron oxidation rate. A trend of decreasing delta56Fe with decreasing Fe (II)(aq) activity is observed, and the water sample with the higher iron concentration among those studied (212 µM/L) shows the delta 56Fe value approaching the iron isotopic composition reported for rocks and soils. A lithogenic source for iron is suggestedI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.