【铅与土壤腐殖酸】Juan Xiong † Luuk K. Koopal †‡ WenFeng Tan *†§ LinChuan Fang § MingXia Wang † Wei Zhao § Fan Liu † Jing Zhang and LiPing Weng . Lead Binding to Soil Fulvic and Humic Acids: NICA-Donnan Modeling and XAFS Spectroscopy. Environ. Sci. Technol. 2013 47 (20) pp 11634–11642

Abstract

Binding of lead (Pb) to soil fulvic acid (JGFA) soil humic acids (JGHA JLHA) and lignite-based humic acid (PAHA) was investigated through binding isotherms and XAFS. Pb binding to humic substances (HS) increased with increasing pH and decreasing ionic strength. The NICA-Donnan model described Pb binding to the HS satisfactorily. The comparison of the model parameters showed substantial differences in median Pb affinity constants among JGFA PAHA and the soil HAs. Milne’s “generic” parameters did not provide an adequate prediction for the soil samples. The Pb binding prediction with generic parameters for the soil HAs was improved significantly by using the value n_Pb1 = 0.92 instead of the generic value n_Pb1 = 0.60. The n_Pb1-n_H1 ratios obtained were relatively high indicating monodentate Pb binding to the carboxylic-type groups. The n_Pb2-n_H2 ratios depended somewhat on the method of optimization but the values were distinctly lower than the n_Pb1-n_H1 rati