In situ measurements of the exchange kinetics of metal complexes in freshwater

摘要：

When in situ measurements were made in a river with high DOC (15mg·L<-1>), using DGT with a range of gel layer thicknes ses, clear kinetic effects were apparent for some metals. The dissociation rates of complexes of Cd, Zn and Pb were too fast to measure by DGT, while there was appreciable kinetic limitation of the dissociation of the complexes of Fe and At. The metal complexes of Mn, Co, Ni and Cu represented an intermediate case, with the kinetic influence increasing systematically from Mn to Cu. Dissociation rate constants, obtained from DGT measurements using an analytical solution of the systems reaction and transport equations, were consistent with the Eigen mechanism for complex dissociation and current understanding of the nature of metal ion binding to fulvic substances. At the low, background concentrations of trace metals that were measured, metals appear to occupy mainly the stronger fraction of binding sites. These measurements highlight the dangers of relying too heavily on equilibrium models, as in this system it was likely that only Cd, Zn and Pb were at true equilibrium. A dynamic, numerical model of the DGT measurement was used to analyse its response to dissociation kinetics in solution, the influence of diffusion coefficients and the nature of the binding layer.

关键词： DGT trace metals humic substances dissociation rates

作者: W. Davison H. Zhang K. W. Warnken J. Galceran J. Puy

作者单位: Department of Environmental Sciences, Lancaster University, Lancaster LAl 4YQ, UK Departamenta de Quimica. Unlversitat de Lleida, (Udl), Av. Rovira Roure, 191. E-25198 Lleida, Catalo

会议类型: 国际会议

会议名称: 第九届痕量元素生物地球化学国际会议(9th International Conference on the Biogeochemistry of Trace Elements)

会议地点: 北京

会议语种:英文

页码: 768-769

在线出版日期: 2007-07-15（万方平台首次上网日期，不代表论文的发表时间）