Investigating the behavior of binding properties between dissolved organic matter (DOM) and Pb(II) during the soil...

Dissolved organic matter (DOM) is the most active component in an environmental system. It can influence the chemical and structural characteristics of soil. In this work, three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy, parallel factor analysis (PARAFAC), and two-dimensional correlation spectroscopy (2D-COS) integrated with synchronous fluorescence were used to explore the interaction between soil-derived DOM and Pb(II) during the soil sorption process. According to the data of batch sorption experiments, the adsorbing capacities of soil, soil + 5 mL DOM, and soil + 10 mL DOM were 16.96, 18.29, and 19.32 mg g^-1, respectively, which indicated that DOM significantly enhanced the adsorption efficiency of Pb(II). The pseudo-second-order kinetic equation could well explain the adsorption process. The adsorbing data conformed to the isotherm of Langmuir adsorption. According to EEM-PARAFAC results, there are two major components from DOM. Protein-like substances were represented by component 1, and humic-like and fulvic-like substances were represented by component 2. Based on 3D-EEM, the results further showed that the intensities of component 1 and component 2 were obviously quenched with the increase of Pb(II) concentrations. The combined interpretations of the 2D-COS map for the DOM revealed that Pb(II) binding might occur sequentially in the order of humic-like fraction > protein-like fraction (346 > 282 nm). According to synchronous fluorescence spectra, static fluorescence quenching was the major process of quenching. Graphical abstract ᅟ.