Earth System Science Research Center, Geographic Institute, Johannes Gutenberg University Mainz, Johann-Joachim-Becher-Weg 21, 55128 Mainz, Germany.
Environ Sci Technol. 2010 Jul 15;44(14):5496-502. doi: 10.1021/es1017653.
The bioavailability, mobility, and toxicity of Cu depend on Cu speciation in solution. In natural systems like soils, sediments, lakes, and river waters, organo-Cu complexes are the dominating species. Organo-complexation of Cu may cause a fractionation of stable Cu isotopes. The knowledge of Cu isotope fractionation during sorption on humic acid may help to better understand Cu isotope fractionation in natural environments and thus facilitate the use of Cu stable isotope ratios (delta(65)Cu) as tracer of the fate of Cu in the environment. We therefore studied Cu isotope fractionation during complexation with insolubilized humic acid (IHA) as a surrogate of humic acid in soil organic matter with the help of sorption experiments at pH 2-7. We used NICA-Donnan chemical speciation modeling to describe Cu binding on IHA and to estimate the influence of Cu binding to different functional groups on Cu isotope fractionation. The observed overall Cu isotope fractionation at equilibrium between the solution and IHA was Delta(65)Cu(IHA-solution) = 0.26 +/- 0.11 per thousand (2SD). Modeled fractionations of Cu isotopes for low- (LAS) and high-affinity sites (HAS) were identical with Delta(65)Cu(LAS/HAS-solution) = 0.27. pH did not influence Cu isotope fractionation in the investigated pH range.
铜的生物利用度、迁移性和毒性取决于其在溶液中的形态。在土壤、沉积物、湖泊和河水等自然系统中，有机铜配合物是主要形态。铜的有机络合作用可能导致稳定铜同位素的分馏。了解腐殖酸吸附过程中铜同位素的分馏作用，有助于更好地理解自然环境中铜同位素的分馏作用，从而促进利用铜稳定同位素比值（δ65Cu）作为环境中铜命运的示踪剂。因此，我们在 pH 值为 2-7 的条件下进行了吸附实验，使用不溶性腐殖酸（IHA）作为土壤有机质中腐殖酸的替代物，研究了铜与腐殖酸络合过程中的铜同位素分馏作用。我们利用 NICA-Donnan 化学形态模型来描述铜在 IHA 上的结合，并估计铜与不同官能团结合对铜同位素分馏的影响。在溶液和 IHA 之间达到平衡时，观察到的铜同位素整体分馏为Δ65Cu（IHA-溶液）= 0.26±0.11‰（2SD）。低亲和性（LAS）和高亲和性（HAS）位点的铜同位素分馏模型相同，为Δ65Cu（LAS/HAS-溶液）= 0.27。在所研究的 pH 范围内，pH 不影响铜同位素分馏。
