Combination of 13C/113Cd NMR, potentiometry, and voltammetry in characterizing the interactions between Cd and two models of the main components of soil organic matter

Lenoble, V.; Garnier, C.; Masion, A.; Ziarelli, F.; Garnier, J. M.
January 2008
Analytical & Bioanalytical Chemistry;Jan2008, Vol. 390 Issue 2, p749
Academic Journal
This work allowed the characterization of the Cd-binding sites of two compounds taken as models for exudates, the main components of soil organic matter (SOM). The studied compounds were exopolysaccharides (EPS), specifically exudates of roots (polygalacturonic acid) and of soil bacteria (Phytagel). Potentiometric acid–base titrations were performed and fitting of the obtained results indicated the presence of two main classes of acidic sites, defined by their p K a values, for both EPS but of a different nature when comparing the two compounds. The two studied exopolysaccharides presented different acidic/basic site ratios: 0.15 for Phytagel and 0.76 for polygalacturonic acid. Spectroscopic techniques (13C/113Cd NMR, FTIR) distinguished different Cd surroundings for each of the studied EPS, which is in agreement with the titration results. Furthermore, these analyses indicated the presence of –COOH and –OH groups in various proportions for each exopolysaccharide, which should be linked to their reactivity towards cadmium. Cadmium titrations (voltammetric measurements) also differentiated different binding sites for each compound and allowed the determination of the strength of the Cd-binding site of the EPS. Fitting of the results of such voltammetric measurements was performed using PROSECE ( Programme d’Optimisation et de Speciation Chimique dans l’Environnement), a software coupling chemical speciation calculation and binding parameter optimization. The fitting, taking into account the Cd2+/H+ competition towards exopolysaccharides, confirmed the acid-base titrations and spectroscopic analyses by revealing two classes of binding sites: (i) one defined as a strong complexant regarding its Cd2+–EPS association (log K = 9–10.4) and with basic functionality regarding H+–EPS association (p K a = 11.3–11.7), and (ii) one defined as a weak complexant (log K = 7.1–8.2) and with acidic functionality (p K a = 3.7–4.0). Therefore the combination of spectroscopic analyses, voltammetry, and fitting allowed the precise characterization of the binding sites of the studied exopolysaccharides, mimicking the main SOM components. Furthermore, the binding parameters obtained by fitting can be used in biogeochemical models to better define the role of key SOM compounds like exudates of roots and of soil bacteria on trace metal transport or assimilation.


Related Articles

  • The disappearance kinetics of fenhexamid in sterile and non-sterile conditions, as revealed by a mixed-effects model analysis. Ottorino-Luca Pantani; Irene Lozzi; Luca Calamai; Samuele Falciani; Marinella Bosetto // Biology & Fertility of Soils;Oct2007, Vol. 44 Issue 1, p131 

    Abstract  A kinetic model was used to evaluate rate and capacity of both sorption and degradation of fenhexamid in four soils under laboratory conditions. This molecule was chosen for its stability to chemical hydrolysis at environmental pH values and its very fast disappearance...

  • Chapter 13: Soil Organic Matter Dynamics. Nieder, Rolf; Benbi, Dinesh K.; lsermann, Klaus // Handbook of Processes & Modeling in the Soil-Plant System;2003, p345 

    The chapter discusses soil organic matter (SOM) dynamics. The factors and processes that affect SOM pool and depletion include climate, soil, aggregation and erosion. Anthropogenic perturbations like land use change can easily disturb the soil equilibrium. It is estimated that 54 Pg is lost in...

  • Spatial variability of nutrient stocks in the humus and soils of a forest massif (Foug?res, France). Arnaud Legout; Christian Walter; Claude Nys // Annals of Forest Science (EDP Sciences);Jan2008, Vol. 65 Issue 1, p108 

    In this study, the spatial distribution of nutrient stocks (K, Ca, Mg and P) was examined in humus and soils at the forest massif scale (Foug?res forest, France). A random stratified sampling plan including 100 sampling points was used and three potential variation factors of nutrient stocks...

  • Net microbial amino sugar accumulation process in soil as influenced by different plant material inputs. Xudong Zhang; Teri Balser // Biology & Fertility of Soils;Oct2007, Vol. 44 Issue 1, p1 

    Abstract  Identifying the impact of plant material inputs on soil amino sugar synthesis may advance our knowledge of microbial transformation processes in soils. In a 12-week laboratory microcosm incubation, 1, 2, 4, and 6% (w/w) soybean leaf or maize stalk were initially added...

  • Investigations of Some Structural Properties of Humic Substances by Fluorescence Quenching. Kenworthy, I. P.; Hayes, M. H. B. // Humic Substances, Peats & Sludges;1997, p39 

    Humic substances (HS) were sequentially and exhaustively isolated from a podzolic Ao horizon. The sequence of solvents used was distilled water, sodium pyrophosphate (Pyro, 0.1M, pH 7), Pyro (0.1M, pH 10.6), and a sodium hydroxide (0.1M)/Pyro (0.1) mixture (pH 12.6) Isolates were fractionated...

  • Natural Abundances of 13C in Soils and Waters. Clapp, C. E.; Layese, M. F.; Hayes, M. H. B.; Huggins, D. R.; Alimaras, R. R. // Humic Substances, Peats & Sludges;1997, p158 

    The δ13C values of soils and humic substances derived from soils, peats, coals, and different waters (soil waters, surface waters, streams, rivers, lakes and an ocean sample) are presented. In addition, data are given that involve soil from an 11 -year experiment on com (Zea mays L.)/soybean...

  • Section 1 : Compositions and Aspects of the Structures of Humic Substances.  // Humic Substances, Peats & Sludges;1997, p1 

    The article introduces several studies concerning the compositions and aspects of the structures of humic substances. There is a discussion on the procedures for isolation and fractionation of humic substances from soils and water. McPhail and Cheshire have described a use of electron spin...

  • Emerging Concepts of the Compositions and Structures of Humic Substances. Hayes, M. H. B. // Humic Substances, Peats & Sludges;1997, p3 

    The innate compositional and structural complexities of humic substances have delayed our awareness of a detailed understanding of the mechanisms by which these operate in soil and water environments. The development of advanced scientific instrumentation, especially in the area of spectroscopy,...

  • Humic Substances from Interment Sites I. Isolation and Characterization. Hayes, M. H. B.; Stewart, Lorraine J.; Bethel, P. // Humic Substances, Peats & Sludges;1997, p136 

    Humic (HA) and fulvic (FA) acid fractions were isolated from grave sites in the Anglo-Saxon burial site at Sutton Hoo using neutral salt (pyrophosphate), base (NaOH), and acidified organic (dimethylsulphoxide/HCl) solvent systems. Properties, such as elemental, sugar, and amino acid...


Read the Article


Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics