Kinetic signatures of metals in the presence of Suwannee River fulvic acid.

This work provides new information on the dissociation kinetics of metal-fulvic acid (FA) complexes. Diffusive gradients in thin-film (DGT) devices deployed in solutions containing metals and 30 mg L(-1) Suwannee River FA at pH 5 and 7, at two different metal-to-ligand ratios, were used to estimate an apparent diffusive boundary layer (ADBL) thickness at the gel-solution interface. The discrepancy between the ADBL thickness measured for metals that are known to dissociate from complexes quickly (e.g., Cd) and that of other trace metals was exploited to calculate the rate of complex dissociation. When the ADBL thickness is plotted for a suite of metals, a "kinetic signature" is created. There was a clear kinetic signature at pH 7, with substantial kinetic limitation for Cu, Pb, and Ni and none for Cd, Co, and Mn (i.e., Cu-, Pb-, and Ni-FA complexes dissociated more slowly). At pH 5, the kinetic signature was less distinct, due in part to slow association kinetics of Mn, and possibly Cd and Co, with the resin. The good sensitivity of the method to small changes in dissociation kinetics was able to show that the dissociation of most metal-FA complexes is sufficiently fast to not limit the DGT measurement.

[1]  Hao Zhang,et al.  Assessment of trace metal binding kinetics in the resin phase of diffusive gradients in thin films. , 2012, Analytica chimica acta.

[2]  Hao Zhang,et al.  Applicability of diffusive gradients in thin films for measuring Mn in soils and freshwater sediments. , 2011, Analytical chemistry.

[3]  Hao Zhang,et al.  Using diffusive gradients in thin films to probe the kinetics of metal interaction with algal exudates , 2011 .

[4]  Hao Zhang,et al.  Contribution of partially labile complexes to the DGT metal flux. , 2011, Environmental science & technology.

[5]  Hao Zhang,et al.  Key role of the resin layer thickness in the lability of complexes measured by DGT. , 2011, Environmental science & technology.

[6]  L. Sigg,et al.  Cadmium speciation and accumulation in periphyton in a small stream with dynamic concentration variations. , 2010, Environmental pollution.

[7]  Hao Zhang,et al.  In situ speciation measurements of trace metals in headwater streams. , 2009, Environmental science & technology.

[8]  C. Chakraborty,et al.  Dynamic DGT speciation analysis and applicability to natural heterogeneous complexes , 2009 .

[9]  Montserrat Filella,et al.  Freshwaters: which NOM matters? , 2009 .

[10]  L. Balistrieri,et al.  Dissolved and labile concentrations of Cd, Cu, Pb, and Zn in the South Fork Coeur d’Alene River, Idaho: Comparisons among chemical equilibrium models and implications for biotic ligand models , 2008 .

[11]  Hao Zhang,et al.  Effects of binding of metals to the hydrogel and filter membrane on the accuracy of the diffusive gradients in thin films technique. , 2008, Analytical chemistry.

[12]  Hao Zhang,et al.  In situ measurements of metal complex exchange kinetics in freshwater. , 2007, Environmental science & technology.

[13]  K. Naqvi,et al.  Estimation of diffusive boundary layer thickness in studies involving diffusive gradients in thin films (DGT) , 2006, Analytical and bioanalytical chemistry.

[14]  W. Tych,et al.  An evaluation of DGT performance using a dynamic numerical model. , 2006, Environmental Science and Technology.

[15]  Hao Zhang,et al.  Accuracy of the diffusive gradients in thin-films technique: diffusive boundary layer and effective sampling area considerations. , 2006, Analytical chemistry.

[16]  Emily R. Unsworth,et al.  Comparison of analytical techniques for dynamic trace metal speciation in natural freshwaters. , 2006, Environmental science & technology.

[17]  Hao Zhang,et al.  Diffusion coefficients of metals and metal complexes in hydrogels used in diffusive gradients in thin films. , 2006 .

[18]  Jacques Buffle,et al.  Dynamic speciation analysis and bioavailability of metals in aquatic systems. , 2005, Environmental science & technology.

[19]  Hao Zhang,et al.  Trace metal measurements in low ionic strength synthetic solutions by diffusive gradients in thin films. , 2005, Analytical chemistry.

[20]  Hao Zhang,et al.  Measurements of Lead Complexation with Organic Ligands using DGT , 2004 .

[21]  Hao Zhang,et al.  Performance characteristics of suspended particulate reagent-iminodiacetate as a binding agent for diffusive gradients in thin films , 2004 .

[22]  Hao Zhang,et al.  In-situ speciation of Ni and Zn in freshwaters: comparison between DGT measurements and speciation models. , 2004, Environmental science & technology.

[23]  Josep Galceran,et al.  Lability and mobility effects on mixtures of ligands under steady-state conditions , 2003 .

[24]  Hao Zhang,et al.  Effect of solution composition, flow and deployment time on the measurement of trace metals by the diffusive gradient in thin films technique. , 2001 .

[25]  J. Galceran,et al.  Voltammetric lability of metal complexes at spherical microelectrodes with various radii. , 2001 .

[26]  R. Gadi,et al.  In situ measurement of dissolved phosphorus in natural waters using DGT , 1998 .

[27]  Hao Zhang,et al.  Performance Characteristics of Diffusion Gradients in Thin Films for the in Situ Measurement of Trace Metals in Aqueous Solution , 1995 .