HAL will be down for maintenance from Friday, June 10 at 4pm through Monday, June 13 at 9am. More information
Skip to Main content Skip to Navigation
Journal articles

Zinc Isotopic Fractionation: Why Organic Matters

Abstract : Zinc isotopic fractionation during adsorption onto a purified humic acid (PHA), an analogue of organic matter (OM), has been investigated experimentally as a function of pH. The Donnan Membrane device (DM) was used to separate Zn bound to the PHA from free Zn2+ ions in solution and allowed us to measure the isotopic ratios of free Zn2+. Below pH 6, adsorption of Zn on the PHA resulted in no measurable isotopic fractionation, while at higher pH, Zn bound to PHA was heavier than free Zn2+ (Delta Zn-66(PHA-FreeZn2+) = +0.24 parts per thousand +/- 0.06 2 sigma, n = 4). This can be explained by changes in Zn speciation with pH, with higher complexation constants and shorter bond lengths for Zn-PHA complex compared to the free Zn2+. Complexation of Zn with PHA occurred mostly through binding to high affinity sites (HAS) and low affinity sites (LAS). Fractionation factors for Zn-66/Zn-64 ratios determined by mass balance calculations were equal to 1.0004 for HAS (alpha(HAS-solution)) and 1.0000 for LAS (alpha(LAS-solution)). Delta 66Zn(OM-FreeZn2+) should then vary according to the heterogeneous nature of the OM, because of the variable relative proportions of these two types of sites. The NICA-Donnan model, along with these fractionation factors and measured delta Zn-66(TotalDissolved), was used to simulate the corresponding isotopic composition of free Zn 21 in the Seine River, France: Delta Zn-66(TotaIDissolved-FreeZn2+) varied from +0.02 parts per thousand to +0.18 parts per thousand, depending on the HAS/LAS ratio assumed for the OM. This study allows a better understanding of Zn isotope fractionation mechanisms associated with organic matter binding.
Complete list of metadata

Contributor : Eva Fareau Connect in order to contact the contributor
Submitted on : Wednesday, July 1, 2020 - 10:21:28 AM
Last modification on : Tuesday, November 16, 2021 - 4:23:50 AM



Delphine Jouvin, Pascale Louvat, Farid Juillot, Chloé Maréchal, Marc Benedetti. Zinc Isotopic Fractionation: Why Organic Matters. Environmental Science and Technology, American Chemical Society, 2009, 43 (15), pp.5747-5754. ⟨10.1021/es803012e⟩. ⟨insu-02885955⟩



Record views