Environmental Chemistry Environmental Chemistry Society
Environmental problems - Chemical approaches
RESEARCH ARTICLE

Modelling proton and metal binding to humic substances with the NICA–EPN model

Andrea C. Montenegro A , Silvia Orsetti B and Fernando V. Molina A C
+ Author Affiliations
- Author Affiliations

A Instituto de Química Física de Materiales, Ambiente y Energía (INQUIMAE) and Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, C1428EGA, Argentina.

B Present address: Institut für Geowissenschaften, Zentrum für angewandte Geowissenschaften, Eberhard-Karls Universität Tübingen, D-72074 Tübingen, Germany.

C Corresponding author. E-mail: fmolina@qi.fcen.uba.ar

Environmental Chemistry 11(3) 318-332 https://doi.org/10.1071/EN13214
Submitted: 26 November 2013  Accepted: 7 March 2014   Published: 10 June 2014

Environmental context. The toxicity of metals in the environment is greatly influenced by natural organic matter owing to its ability to bind metals to form complexes that can be immobile and non-bioavailable. Sound mathematical models are important to reliably predict the behaviour of such contaminants, and how they are affected by organic matter and other environmental colloids. Here a new model is discussed and compared with precedent ones.

Abstract. The mathematical modelling of metal cation–natural organic matter interactions is a fundamental tool in predicting the state and fate of pollutants in the environment. In this work, the binding of protons and metal cations to humic substances is modelled applying the Elastic Polyelectrolyte Network (EPN) electrostatic model with the Non-Ideal Competitive Adsorption (NICA) isotherm as the intrinsic part (NICA–EPN model). Literature data of proton and metal binding to humic substances at different pH and ionic strength values are analysed, discussing in depth the model predictions. The NICA–EPN model is found to describe well these phenomena. The electrostatic contribution to the Gibbs free energy of adsorbate–humic interaction in the EPN model is lower than that predicted by the Donnan phase model; the intrinsic mean binding constants for protons and metal cations are generally higher, closer to independent estimations and to the range of acid–base and complexation equilibrium values for common carboxylic acids. The results for metal cations are consistent with recent literature findings. The model predicts shrinking of the humic particles with increased metal binding, as a consequence of net charge decrease.


References

[1]  J. Ephraim, S. Alegret, A. Mathuthu, M. Bicking, R. L. Malcolm, J. A. Marinsky, A unified physicochemical description of the protonation and metal ion complexation equilibria of natural organic acids (humic and fulvic acids). 2. Influence of polyelectrolyte properties and functional group heterogeneity on the protonation equilibria of fulvic acid. Environ. Sci. Technol. 1986, 20, 354.
A unified physicochemical description of the protonation and metal ion complexation equilibria of natural organic acids (humic and fulvic acids). 2. Influence of polyelectrolyte properties and functional group heterogeneity on the protonation equilibria of fulvic acid.CrossRef | 1:CAS:528:DyaL28Xht1yrur8%3D&md5=a8e97adb3a62b54d789a57662f0d2296CAS | 22300206PubMed |

[2]  N. Senesi, E. Loffredo, Metal ion complexation by humic substances, in Chemical Processes in Soils (Eds M. A. Tabatabai, D. L. Sparks) 2005, pp. 563–617 (Soil Science Society of America: Madison, WI).

[3]  S. Sen Gupta, K. G. Bhattacharyya, Kinetics of adsorption of metal ions on inorganic materials: a review. Adv. Colloid Interface Sci. 2011, 162, 39.
Kinetics of adsorption of metal ions on inorganic materials: a review.CrossRef | 1:CAS:528:DC%2BC3MXitFaks70%3D&md5=8f3fb64868c600e6a9e352d35c8dcf15CAS | 21272842PubMed |

[4]  C. E. Clapp, M. H. B. Hayes, A. J. Simpson, W. L. Kingery, Chemistry of soil organic matter, in Chemical Processes in Soils (Eds M. A. Tabatabai, D. L. Sparks) 2005, pp. 1–150 (Soil Science Society of America: Madison, WI).

[5]  J. A. Baldock, P. N. Nelson, Soil organic matter, in Handbook of Soil Science (Ed. M. L. Sumner) 1999, pp. B75–B84 (CRC: Boca Raton, Fl).

[6]  Á. Zsolnay, Dissolved organic matter: artefacts, definitions, and functions. Geoderma 2003, 113, 187.
Dissolved organic matter: artefacts, definitions, and functions.CrossRef | 1:CAS:528:DC%2BD3sXhsF2nsL0%3D&md5=c952bfa81692041c8e230994bb2a3b76CAS |

[7]  S. Orsetti, E. M. Andrade, F. V. Molina, Application of a constrained regularization method to extraction of affinity distributions: proton and metal binding to humic substances. J. Colloid Interface Sci. 2009, 336, 377.
Application of a constrained regularization method to extraction of affinity distributions: proton and metal binding to humic substances.CrossRef | 1:CAS:528:DC%2BD1MXnslKntbs%3D&md5=7fe5722ead4e114e42c4548f0f41cc30CAS | 19477457PubMed |

[8]  A. J. Simpson, W. L. Kingery, M. H. Hayes, M. Spraul, E. Humpfer, P. Dvortsak, R. Kerssebaum, M. Godejohann, M. Hofmann, Molecular structures and associations of humic substances in the terrestrial environment. Naturwissenschaften 2002, 89, 84.
Molecular structures and associations of humic substances in the terrestrial environment.CrossRef | 1:CAS:528:DC%2BD38XivVaktbk%3D&md5=dc05875da76678045e5a885efb908ad2CAS | 12046627PubMed |

[9]  M. Hosse, K. J. Wilkinson, Determination of electrophoretic mobilities and hydrodynamic radii of three humic substances as a function of pH and ionic strength. Environ. Sci. Technol. 2001, 35, 4301.
Determination of electrophoretic mobilities and hydrodynamic radii of three humic substances as a function of pH and ionic strength.CrossRef | 1:CAS:528:DC%2BD3MXnt12qu7g%3D&md5=40508adb77c49037fa127261a6b7cc36CAS | 11718346PubMed |

[10]  J. F. L. Duval, K. J. Wilkinson, H. P. Van Leeuwen, J. Buffle, Humic substances are soft and permeable: evidence from their electrophoretic mobilities. Environ. Sci. Technol. 2005, 39, 6435.
Humic substances are soft and permeable: evidence from their electrophoretic mobilities.CrossRef | 1:CAS:528:DC%2BD2MXjvFKjs70%3D&md5=0cb37785d6eacf43bdf7ffc36464e935CAS |

[11]  J. Buffle, R. S. Altmann, M. Filella, A. Tessier, Complexation by natural heterogeneous compounds: site occupation distribution functions, a normalized description of metal complexation. Geochim. Cosmochim. Acta 1990, 54, 1535.
Complexation by natural heterogeneous compounds: site occupation distribution functions, a normalized description of metal complexation.CrossRef | 1:CAS:528:DyaK3cXltlWit7k%3D&md5=fff2db5feab66509a41d676066f27678CAS |

[12]  E. Tipping, Humic Ion-Binding Model VI: an improved description of the interactions of protons and metal ions with humic substances. Aquat. Geochem. 1998, 4, 3.
Humic Ion-Binding Model VI: an improved description of the interactions of protons and metal ions with humic substances.CrossRef | 1:CAS:528:DyaK1cXntlSjuro%3D&md5=5713777c9b890be10b9003a0b7744eadCAS |

[13]  J. P. Gustafsson, P. Pechova, D. Berggren, Modeling metal binding to soils: the role of natural organic matter. Environ. Sci. Technol. 2003, 37, 2767.
Modeling metal binding to soils: the role of natural organic matter.CrossRef | 1:CAS:528:DC%2BD3sXjsleisbw%3D&md5=b708dbd7eef51eea8e669cece1b1071bCAS | 12854717PubMed |

[14]  S. Goldberg, Equations and models describing adsorption processes in soils, in Chemical Processes in Soils (Eds M. A. Tabatabai, D. L. Sparks) 2005, pp. 489–518 (Soil Science Society of America: Madison, WI).

[15]  F. V. Molina, Soil Colloids: Properties and Ion Binding 2013 (CRC Press: Boca Raton, FL).

[16]  E. Tipping, S. Lofts, J. E. Sonke, Humic Ion-Binding Model VII: a revised parameterisation of cation-binding by humic substances. Environ. Chem. 2011, 8, 225.
Humic Ion-Binding Model VII: a revised parameterisation of cation-binding by humic substances.CrossRef | 1:CAS:528:DC%2BC3MXptVWrsL0%3D&md5=aa4916d59483661845fa4dc20916cb11CAS |

[17]  D. G. Kinniburgh, C. J. Milne, M. F. Benedetti, J. P. Pinheiro, J. Filius, L. K. Koopal, W. H. Van Riemsdijk, Metal ion binding by humic acid: application of the NICA–Donnan model. Environ. Sci. Technol. 1996, 30, 1687.
Metal ion binding by humic acid: application of the NICA–Donnan model.CrossRef | 1:CAS:528:DyaK28XhvVKgtL4%3D&md5=536da0cbf5b4a863361015222378d00eCAS |

[18]  M. F. Benedetti, W. H. Van Riemsdijk, L. K. Koopal, Humic substances considered as a heterogeneous Donnan gel phase. Environ. Sci. Technol. 1996, 30, 1805.
Humic substances considered as a heterogeneous Donnan gel phase.CrossRef | 1:CAS:528:DyaK28XisFans7Y%3D&md5=40c3e7e762ab48271f3874128ecb1828CAS |

[19]  C. J. Milne, D. G. Kinniburgh, W. H. van Riemsdijk, E. Tipping, Generic NICA–Donnan model parameters for metal-ion binding by humic substances. Environ. Sci. Technol. 2003, 37, 958.
Generic NICA–Donnan model parameters for metal-ion binding by humic substances.CrossRef | 1:CAS:528:DC%2BD3sXosVWgsQ%3D%3D&md5=cf83eea77d60eafc37b6d7ddffabaf09CAS | 12666927PubMed |

[20]  J. B. Christensen, E. Tipping, D. G. Kinniburgh, C. Grøn, T. H. Christensen, Proton binding by groundwater fulvic acids of different age, origins, and structure modeled with the model V and NICA–Donnan model. Environ. Sci. Technol. 1998, 32, 3346.
Proton binding by groundwater fulvic acids of different age, origins, and structure modeled with the model V and NICA–Donnan model.CrossRef | 1:CAS:528:DyaK1cXlvFKmu7g%3D&md5=0935c34cf8c7a4237070307c307d3de8CAS |

[21]  M. J. Avena, A. W. P. Vermeer, L. K. Koopal, Volume and structure of humic acids studied by viscometry pH and electrolyte concentration effects. Colloids Surf. A Physicochem. Eng. Asp. 1999, 151, 213.
Volume and structure of humic acids studied by viscometry pH and electrolyte concentration effects.CrossRef | 1:CAS:528:DyaK1MXhvV2nsL8%3D&md5=5be201b79c65ab831f50adc9a544bf9dCAS |

[22]  G. Chilom, J. A. Rice, Structural organization of humic acid in the solid state. Langmuir 2009, 25, 9012.
Structural organization of humic acid in the solid state.CrossRef | 1:CAS:528:DC%2BD1MXlt1GqsrY%3D&md5=c1bcf6a99dbbc2f3cab5cf02fef36011CAS | 19408899PubMed |

[23]  S. Orsetti, E. M. Andrade, F. V. Molina, Modeling ion binding to humic substances: Elastic Polyelectrolyte Network model. Langmuir 2010, 26, 3134.
Modeling ion binding to humic substances: Elastic Polyelectrolyte Network model.CrossRef | 1:CAS:528:DC%2BC3cXhvVKgsw%3D%3D&md5=4034ddc64958edf073a44b8af0d64cb6CAS | 20055366PubMed |

[24]  S. Orsetti, J. L. Marco-Brown, E. M. Andrade, F. V. Molina, PbII binding to humic substances: an equilibrium and spectroscopic study. Environ. Sci. Technol. 2013, 47, 8325.
| 1:CAS:528:DC%2BC3sXhtVWhtL7J&md5=174b568105dab964c4678912e130a5b5CAS | 23805795PubMed |

[25]  T. L. Hill, Some statistical mechanical models of elastic polyelectrolytes and proteins. J. Chem. Phys. 1952, 20, 1259.
Some statistical mechanical models of elastic polyelectrolytes and proteins.CrossRef | 1:CAS:528:DyaG3sXlslCntQ%3D%3D&md5=3c45d41cb676f06c34e3f036c3872cfeCAS |

[26]  E. Dinar, T. F. Mentel, Y. Rudich, The density of humic acids and humic like substances (HULIS) from fresh and aged wood burning and pollution aerosol particles. Atmos. Chem. Phys. 2006, 6, 5213.
The density of humic acids and humic like substances (HULIS) from fresh and aged wood burning and pollution aerosol particles.CrossRef | 1:CAS:528:DC%2BD2sXht1eitrc%3D&md5=1689ab35e13ad84ad49011d77940db16CAS |

[27]  C. J. Milne, D. G. Kinniburgh, E. Tipping, Generic NICA–Donnan model parameters for proton binding by humic substances. Environ. Sci. Technol. 2001, 35, 2049.
Generic NICA–Donnan model parameters for proton binding by humic substances.CrossRef | 1:CAS:528:DC%2BD3MXis1GrsLY%3D&md5=58397a135dc43f51409b0d76c10d44e2CAS | 11393987PubMed |

[28]  A. Matynia, T. Lenoir, B. Causse, L. Spadini, T. Jacquet, A. Manceau, Semi-empirical proton binding constants for natural organic matter. Geochim. Cosmochim. Acta 2010, 74, 1836.
Semi-empirical proton binding constants for natural organic matter.CrossRef | 1:CAS:528:DC%2BC3cXhvFalurw%3D&md5=544abb97b995be8ebb628cf678535ddcCAS |

[29]  P. J. Flory, Themodynamics of high polymer solutions. J. Chem. Phys. 1942, 10, 51.
Themodynamics of high polymer solutions.CrossRef | 1:CAS:528:DyaH38Xns1Gk&md5=376b185f0eb6adaaceb38c842e84fde4CAS |

[30]  P. J. Flory, Statistical mechanics of swelling of network structures. J. Chem. Phys. 1950, 18, 108.
Statistical mechanics of swelling of network structures.CrossRef | 1:CAS:528:DyaG3cXivFanuw%3D%3D&md5=6e5360c8ca0de19c160d2374c170bc23CAS |

[31]  D. G. Kinniburgh, W. H. Van Riemsdijk, L. K. Koopal, M. Borkovec, M. F. Benedetti, M. J. Avena, Ion binding to natural organic matter: competition, heterogeneity, stoichiometry and thermodynamic consistency. Colloids Surf. A Physicochem. Eng. Asp. 1999, 151, 147.
Ion binding to natural organic matter: competition, heterogeneity, stoichiometry and thermodynamic consistency.CrossRef | 1:CAS:528:DyaK1MXhvV2ns7g%3D&md5=64109cfc9410b76e41a4b38ad41bba0bCAS |

[32]  B. Pernet-Coudrier, E. Companys, J. Galceran, M. Morey, J.-M. Mouchel, J. Puy, N. Ruiz, G. Varrault, Pb-binding to various dissolved organic matter in urban aquatic systems: key role of the most hydrophilic fraction. Geochim. Cosmochim. Acta 2011, 75, 4005.
Pb-binding to various dissolved organic matter in urban aquatic systems: key role of the most hydrophilic fraction.CrossRef | 1:CAS:528:DC%2BC3MXns1Cnu78%3D&md5=11ceb7b507bc6418866cb43614000b02CAS |

[33]  E. Companys, J. Puy, J. Galceran, Humic acid complexation to Zn and Cd determined with the new electroanalytical technique AGNES. Environ. Chem. 2007, 4, 347.
| 1:CAS:528:DC%2BD2sXht1yiu7jK&md5=b7532dde9dda0c7cd9f185cc491192d2CAS |

[34]  I. Christl, Ionic strength- and pH-dependence of calcium binding by terrestrial humic acids. Environ. Chem. 2012, 9, 89.
Ionic strength- and pH-dependence of calcium binding by terrestrial humic acids.CrossRef | 1:CAS:528:DC%2BC38Xis1amtLc%3D&md5=679a8b042796877c66ac6fbf7b2b3318CAS |

[35]  C. W. Davies, Ion Association 1962 (Butterworths: London).

[36]  M. I. A. Lourakis, Levmar: Levenberg-Marquardt Nonlinear Least Squares Algorithms in C/C++ 2004 (Institute of Computer Science, FORTH: Heraklion, Crete, Greece).

[37]  J. P. Gustafsson, Visual Minteq. 2011 (KTH, Department of Land and Water Resources Engineering.: Stockholm, Sweden).

[38]  V. T. Athavale, L. H. Prabhu, D. G. Vartak, Solution stability constants of some metal complexes of derivatives of catechol. J. Inorg. Nucl. Chem. 1966, 28, 1237.
Solution stability constants of some metal complexes of derivatives of catechol.CrossRef | 1:CAS:528:DyaF28XktVSmtLo%3D&md5=eb6c7a0c6dac72e839713ee8e778146cCAS |

[39]  E. Furia, R. Porto, The hydrogen salicylate ion as ligand. complex formation equilibria with dioxouranium(VI), neodymium(III) and lead(II). Ann. Chim. 2004, 94, 795.
The hydrogen salicylate ion as ligand. complex formation equilibria with dioxouranium(VI), neodymium(III) and lead(II).CrossRef | 1:CAS:528:DC%2BD2cXhtVOmtLrN&md5=e7d869e4ba8df9f4544deafef3f5fcb5CAS | 15626240PubMed |

[40]  J. P. Gustafsson, Modeling the acid-base properties and metal complexation of humic substances with the Stockholm Humic Model. J. Colloid Interface Sci. 2001, 244, 102.
Modeling the acid-base properties and metal complexation of humic substances with the Stockholm Humic Model.CrossRef | 1:CAS:528:DC%2BD3MXot1KisLw%3D&md5=c17d1ca37696e340e9ed673f5af5ff1aCAS |

[41]  T. Lenoir, A. Matynia, A. Manceau, Convergence-optimized procedure for applying the NICA–Donnan model to potentiometric titrations of humic substances. Environ. Sci. Technol. 2010, 44, 6221.
Convergence-optimized procedure for applying the NICA–Donnan model to potentiometric titrations of humic substances.CrossRef | 1:CAS:528:DC%2BC3cXptVygsLo%3D&md5=290339532ffe81884336436adb34ca52CAS | 20704219PubMed |

[42]  M. J. Avena, L. K. Koopal, W. H. van Riemsdijk, Proton binding to humic acids: electrostatic and intrinsic interactions. J. Colloid Interface Sci. 1999, 217, 37.
Proton binding to humic acids: electrostatic and intrinsic interactions.CrossRef | 1:CAS:528:DyaK1MXltVaht7s%3D&md5=805840c7699fb7b6a74ad2a1a803aa06CAS | 10441409PubMed |

[43]  M. B. Hay, S. C. B. Myneni, Structural environments of carboxyl groups in natural organic molecules from terrestrial systems. Part 1. Infrared spectroscopy. Geochim. Cosmochim. Acta 2007, 71, 3518.
Structural environments of carboxyl groups in natural organic molecules from terrestrial systems. Part 1. Infrared spectroscopy.CrossRef | 1:CAS:528:DC%2BD2sXnsVSrtb0%3D&md5=33c58391377dd11b0910b285b49d78b8CAS |

[44]  Y. B. Atalay, R. F. Carbonaro, D. M. Di Toro, Distribution of proton dissociation constants for model humic and fulvic acid molecules. Environ. Sci. Technol. 2009, 43, 3626.
Distribution of proton dissociation constants for model humic and fulvic acid molecules.CrossRef | 1:CAS:528:DC%2BD1MXkslaktbg%3D&md5=66ec3bf3159709781287591afaffda51CAS | 19544864PubMed |

[45]  A. P. Deshmukh, C. Pacheco, M. B. Hay, S. C. B. Myneni, Structural environments of carboxyl groups in natural organic molecules from terrestrial systems. Part 2: 2-D NMR spectroscopy. Geochim. Cosmochim. Acta 2007, 71, 3533.
Structural environments of carboxyl groups in natural organic molecules from terrestrial systems. Part 2: 2-D NMR spectroscopy.CrossRef | 1:CAS:528:DC%2BD2sXnsVSrtbo%3D&md5=7dd02d58103baf9c3c681f92f299d577CAS |

[46]  A. Kirishima, T. Ohnishi, N. Sato, O. Tochiyama, Determination of the phenolic-group capacities of humic substances by non-aqueous titration technique. Talanta 2009, 79, 446.
Determination of the phenolic-group capacities of humic substances by non-aqueous titration technique.CrossRef | 1:CAS:528:DC%2BD1MXnvVClsbk%3D&md5=ccb71d0df2d54aec114f783bb34b6f2dCAS | 19559903PubMed |

[47]  N. Senesi, E. Loffredo, The chemistry of soil organic matter, in Soil Physical Chemistry (Ed. D. L. Sparks) 1998, pp. 239–370 (CRC Press: Boca Raton, Fl).

[48]  J. P. Pinheiro, A. M. Mota, M. F. Benedetti, Effect of aluminum competition on lead and cadmium binding to humic acids at variable ionic strength. Environ. Sci. Technol. 2000, 34, 5137.
Effect of aluminum competition on lead and cadmium binding to humic acids at variable ionic strength.CrossRef | 1:CAS:528:DC%2BD3cXnvFartb4%3D&md5=9c4ee02c45eb9ab86b97b1133fcfeb9cCAS |

[49]  W. H. Otto, S. D. Burton, W. Robert Carper, C. K. Larive, Examination of cadmium(II) complexation by the Suwannee River fulvic acid using 113Cd NMR relaxation measurements. Environ. Sci. Technol. 2001, 35, 4900.
Examination of cadmium(II) complexation by the Suwannee River fulvic acid using 113Cd NMR relaxation measurements.CrossRef | 1:CAS:528:DC%2BD3MXotlWiu7Y%3D&md5=dd937ace77221ef88bfdccff7723e606CAS | 11775168PubMed |

[50]  K. Xia, W. Bleam, P. A. Helmke, Studies of the nature of Cu2+ and Pb2+ binding sites in soil humic substances using X-ray absorption spectroscopy. Geochim. Cosmochim. Acta 1997, 61, 2211.
Studies of the nature of Cu2+ and Pb2+ binding sites in soil humic substances using X-ray absorption spectroscopy.CrossRef | 1:CAS:528:DyaK2sXjvFSksbY%3D&md5=1e1abd844664e446f0e1da1ec4d5982cCAS |

[51]  A. Terbouche, C. A. Ramdane-Terbouche, D. Hauchard, S. Djebbar, Evaluation of adsorption capacities of humic acids extracted from Algerian soil on polyaniline for application to remove pollutants such as CdII, ZnII and NiII and characterization with cavity microelectrode. J. Environ. Sci. (China) 2011, 23, 1095.
Evaluation of adsorption capacities of humic acids extracted from Algerian soil on polyaniline for application to remove pollutants such as CdII, ZnII and NiII and characterization with cavity microelectrode.CrossRef | 1:CAS:528:DC%2BC3MXhtVyru7nP&md5=2607418634cd3d976c48931b41a6531dCAS | 22125901PubMed |

[52]  T. Karlsson, P. Persson, U. Skyllberg, Complexation of copper(II) in organic soils and in dissolved organic matter – EXAFS evidence for chelate ring structures. Environ. Sci. Technol. 2006, 40, 2623.
Complexation of copper(II) in organic soils and in dissolved organic matter – EXAFS evidence for chelate ring structures.CrossRef | 1:CAS:528:DC%2BD28XisFWjt78%3D&md5=cb5938cb982c4e71c50f0dfa8dffe0e3CAS | 16683601PubMed |

[53]  J. Xiong, L. K. Koopal, W. Tan, L. Fang, M. Wang, W. Zhao, F. Liu, J. Zhang, L. P. Weng, Lead binding to soil fulvic and humic acids: NICA–Donnan modeling and XAFS spectroscopy. Environ. Sci. Technol. 2013, 47, 11634.
Lead binding to soil fulvic and humic acids: NICA–Donnan modeling and XAFS spectroscopy.CrossRef | 1:CAS:528:DC%2BC3sXhsVCmu7rP&md5=783f9a974f3f63820d3502dbf8eef7bbCAS | 24040886PubMed |

[54]  J. Puy, J. Galceran, C. Huidobro, E. Companys, N. Samper, J. L. Garcés, F. Mas, Conditional affinity spectra of Pb2+–humic acid complexation from data obtained with AGNES. Environ. Sci. Technol. 2008, 42, 9289.
Conditional affinity spectra of Pb2+–humic acid complexation from data obtained with AGNES.CrossRef | 1:CAS:528:DC%2BD1cXhtlKqtLjI&md5=fa913aefacf5cf7cdbac233317dc8a98CAS | 19174906PubMed |

[55]  A. Manceau, M.-C. Boisset, G. Sarret, J.-L. Hazemann, M. Mench, P. Cambier, R. Prost, Direct determination of lead speciation in contaminated soils by EXAFS spectroscopy. Environ. Sci. Technol. 1996, 30, 1540.
Direct determination of lead speciation in contaminated soils by EXAFS spectroscopy.CrossRef | 1:CAS:528:DyaK28XhvVKgt70%3D&md5=b729fe61c1c989e1633c56e70b4bc711CAS |

[56]  Y. Arai, A. R. Rick, T. Saylor, E. Faas, R. Tappero, A. Lanzirotti, Macroscopic and molecular-scale assessment of soil lead contamination impacted by seasonal dove hunting activities. J. Soils Sediments 2011, 11, 968.
Macroscopic and molecular-scale assessment of soil lead contamination impacted by seasonal dove hunting activities.CrossRef | 1:CAS:528:DC%2BC3MXhtVegtLnL&md5=5b7c16d811b40a346b2f16f8f5acc919CAS |

[57]  A. P. Robertson, Goethite/Humic Acid Interactions and their Effects on Copper(II) Binding 1996, Ph.D. Thesis, Stanford University, Stanford, CA.

[58]  P. H. Hsu, T. F. Bates, Formation of X-ray amorphous and crystalline aluminium hydroxides. Mineral. Mag. 1964, 33, 749.
Formation of X-ray amorphous and crystalline aluminium hydroxides.CrossRef | 1:CAS:528:DyaF2cXovFCqsg%3D%3D&md5=c17c006d6a80cc20d5162f8cbc56d944CAS |

[59]  B. Stolpe, L. Guo, A. M. Shiller, G. R. Aiken, Abundance, size distributions and trace-element binding of organic and iron-rich nanocolloids in Alaskan rivers, as revealed by field-flow fractionation and ICP-MS. Geochim. Cosmochim. Acta 2013, 105, 221.
Abundance, size distributions and trace-element binding of organic and iron-rich nanocolloids in Alaskan rivers, as revealed by field-flow fractionation and ICP-MS.CrossRef | 1:CAS:528:DC%2BC3sXivVKht70%3D&md5=e632ec4c6aeaba479a1f7014799f140eCAS |

[60]  W. Tan, J. Xiong, Y. Li, M. Wang, L. Weng, L. K. Koopal, Proton binding to soil humic and fulvic acids: experiments and NICA–Donnan modeling. Colloids Surf. A Physicochem. Eng. Asp. 2013, 436, 1152.
Proton binding to soil humic and fulvic acids: experiments and NICA–Donnan modeling.CrossRef | 1:CAS:528:DC%2BC3sXhs1SgurvE&md5=8a38ecac940586ceaacb5083104e6f86CAS |

[61]  B. A. Browne, C. T. Driscoll, pH-dependent binding of aluminum by a fulvic acid. Environ. Sci. Technol. 1993, 27, 915.
pH-dependent binding of aluminum by a fulvic acid.CrossRef | 1:CAS:528:DyaK3sXitF2isLw%3D&md5=211c56e8eb0532dfeac4d039149c6dcaCAS |

[62]  J. P. Pinheiro, A. M. Mota, M. F. Benedetti, Lead and calcium binding to fulvic acids: salt effect and competition. Environ. Sci. Technol. 1999, 33, 3398.
Lead and calcium binding to fulvic acids: salt effect and competition.CrossRef | 1:CAS:528:DyaK1MXlsVKltbw%3D&md5=ee52e3c8c86553c2b0cab6f7a2b1095eCAS |

[63]  S. E. Cabaniss, M. S. Shuman, Copper binding by dissolved organic matter: I. Suwannee River fulvic acid equilibria. Geochim. Cosmochim. Acta 1988, 52, 185.
Copper binding by dissolved organic matter: I. Suwannee River fulvic acid equilibria.CrossRef | 1:CAS:528:DyaL1cXhtFynt7k%3D&md5=3bf69580bdaf055496cb0e95420dc1ceCAS |

[64]  I. Christl, C. J. Milne, D. G. Kinniburgh, R. Kretzschmar, Relating ion binding by fulvic and humic acids to chemical composition and molecular size. 2. Metal binding. Environ. Sci. Technol. 2001, 35, 2512.
Relating ion binding by fulvic and humic acids to chemical composition and molecular size. 2. Metal binding.CrossRef | 1:CAS:528:DC%2BD3MXjtlClu7k%3D&md5=bc7797612767288484158c03379edf18CAS | 11432556PubMed |

[65]  M. F. Benedetti, C. J. Milne, D. G. Kinniburgh, W. H. Van Riemsdijk, L. K. Koopal, Metal ion binding to humic substances: application of the non-ideal competitive adsorption model. Environ. Sci. Technol. 1995, 29, 446.
Metal ion binding to humic substances: application of the non-ideal competitive adsorption model.CrossRef | 1:CAS:528:DyaK2MXivFOrs7s%3D&md5=cafbac173ab674054df7988e10560390CAS | 22201392PubMed |

[66]  A. M. Mota, A. Rato, C. Brazia, M. L. S. Gonçalves, Competition of Al3+ in complexation of humic matter with Pb2+: a comparative study with other ions. Environ. Sci. Technol. 1996, 30, 1970.
Competition of Al3+ in complexation of humic matter with Pb2+: a comparative study with other ions.CrossRef | 1:CAS:528:DyaK28XisFansLk%3D&md5=5cf257ab64267bfdd25bbc7b1c3609a9CAS |

[67]  C. Plaza, N. Senesi, A. Polo, G. Brunetti, Acid-base properties of humic and fulvic acids formed during composting. Environ. Sci. Technol. 2005, 39, 7141.
Acid-base properties of humic and fulvic acids formed during composting.CrossRef | 1:CAS:528:DC%2BD2MXntVeru7c%3D&md5=0ab8e38fd6072c9b84ea7ed62cc25ee7CAS | 16201640PubMed |

[68]  J. D. Ritchie, E. M. Perdue, Proton-binding study of standard and reference fulvic acids, humic acids, and natural organic matter. Geochim. Cosmochim. Acta 2003, 67, 85.
Proton-binding study of standard and reference fulvic acids, humic acids, and natural organic matter.CrossRef | 1:CAS:528:DC%2BD38XpsV2ktLY%3D&md5=b5fe89388154abbf87a8f70eb13e1886CAS |



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