Fractionation of Cu and Zn isotopes during adsorption onto amorphous Fe(III) oxyhydroxide: Experimental mixing of acid rock drainage and ambient river water

The influence of weathering and soil organic matter on Zn isotopes in soils

“…However, in Icelandic soils, there is no correlation between the δ 66 Zn of the soils and the Fe oxide content estimated from the Fe d /Fe t ratio (R 2 = 0.03). There is no correlation either between the δ 66 Zn of soils and the proportion of poorly crystalline Fe-oxides estimated from the Fe o /Fe d ratio (R 2 = 0.02), despite the fact that a higher fractionation factor is reported for poorly crystalline Fe-oxides than for crystalline Fe-oxides (Juillot et al, 2008;Balistrieri et al, 2008). Therefore, interaction between Zn and Fe-oxides appears not to be a major controlling factor on the Zn isotope variations in these soils.…”

“…The stable isotopes of Zn provide the potential to better understand interactions between Zn and soil constituents, including metal oxides (Juillot et al, 2008;Balistrieri et al, 2008;Bryan et al, 2015;Pokrovsky et al, 2005), phyllosilicates (Guinoiseau et al, 2016), and organic matter (Jouvin et al, 2009;Gélabert et al, 2006;Kafantaris and Borrok, 2014;John and Conway, 2014). Heavy Zn isotopes are preferentially adsorbed on to the surface of Mn-oxides (birnessite; Bryan et al, 2015) and Fe-oxides, with a higher fractionation factor for poorly crystalline Fe-oxides (ferrihydrite) than for crystalline Fe-oxides (goethite) (Juillot et al, 2008;Balistrieri et al, 2008). Heavy Zn isotopes are also preferentially retained by sorption onto kaolinite (Guinoiseau et al, 2016).…”

“…However, there is no evidence for the presence of sulfides in the studied soils, and no volcanic hydrothermal system in the vicinity of the site, so any contribution from Zn isotope fractionation associated with sulfides (e.g., Fujii et al, 2011;Chen et al, 2014) is considered unlikely. Zinc isotopes in soils may be fractionated by adsorption onto Feoxides (Juillot et al, 2008;Balistrieri et al, 2008;Pokrovsky et al, 2005), with heavy Zn isotopes being preferentially adsorbed at the surface of Fe-oxides. However, in Icelandic soils, there is no correlation between the δ 66 Zn of the soils and the Fe oxide content estimated from the Fe d /Fe t ratio (R 2 = 0.03).…”

Cu isotopic compositions in Elsholtzia splendens: Influence of soil condition and growth period on Cu isotopic fractionation in plant tissue

“…In the EDDS soils, Cu is therefore expected to be present mainly as a complex with EDDS in the soil solution. As equatorial Cu-O/N bonds are shorter than the bonds in aquo complexes (Harding, 1999;Korshin et al, 1998;Sheals et al, 2001;Xia et al, 1997) and 65 Cu is enriched in the species in which Cu is more strongly bound, heavy Cu isotope are expected to be partitioned into Cu − EDDS species in EDDS and S + EDDS soil solutions relative to the soil solution (Balistrieri et al, 2008;Pokrovsky et al, 2008), resulting in light Cu isotope enrichment in the phytoavailable component of EDDS and S + EDDS soil solutions based on mass balance. In soil solutions with added S, heavy Cu isotope is expected to be partitioned into free Cu ion species due to the oxidation of elemental S (Nor and Tabatabai, 1977), which causes preferential heavy isotope enrichment in free Cu ion species.…”

“…Even without accurate Cu isotopic fractionation data, it seems likely that heavy enrichment occurs in aboveground tissue through the xylem relative to root tissue. Both complexation and oxidation products tend to be heavy isotope enriched; e.g., 0.27‰ Cu isotopic fractionation for complexation (Bigalke et al, 2010), and + 1.9‰ to +5.3‰ for oxidation (Asael et al, 2007;Balistrieri et al, 2008;Mathur et al, 2005). As the magnitude of fractionation induced by Cu complexation in plants is expected to be small, it appears likely that Cu(I) is oxidized to Cu(II) at the interface between root (apoplast) and xylem (symplasm).…”