期刊
WATER RESEARCH
卷 144, 期 -, 页码 435-443出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.watres.2018.07.062
关键词
Differential spectra; Dissolved organic matter; Heavy metals; NICA-Donnan model; Two dimensional heterospectral correlation analysis
资金
- National Natural Science Foundation of China [51479187]
- University of Wisconsin Milwaukee [RGI-101X318]
- Youth Innovation Promotion Association CAS [2016286]
- Open Research Foundation of Key Laboratory of the Pearl River Estuarine Dynamics and Associated Process Regulation, Ministry of Water Resources [2018KJ02]
Dissolved organic matter (DOM) in aquatic environment significantly influences the behavior and fate of heavy metals via binding, complexation and thus changes the metal speciation; however detailed interfacial processes and mechanisms are still unclear. Here, differential absorbance and fluorescence spectra and two dimensional UV-FTIR heterospectral correlation analysis were applied to probe into the Pb(II)-DOM interaction at a wide range of pH and ionic strength (IS). The absorbance of DOM molecules under all conditions increased with metal addition, while the different extents of absorbance variations along the wavelength range in the differential zero-order and log-transformed absorbance spectra indicated the site heterogeneity within the DOM pool for metal binding. Spectral parameters, namely differential fluorescent components 1 and 2 (DFC1 and DFC2) and differential slopes of log-transformed absorbance in the range of wavelength 350-400 nm (DSlope(350-400)) were found to be highly correlated with the total amounts of DOM-bound Pb(II) predicted by the NICA-Donnan model, while the differential absorbance spectra at 235 nm (DA(235)) was related to the extent of Pb(II) bound by carboxylic groups. Thus, these parameters are an indicator or proxy for the in situ Pb(II)-DOM interaction extent. Aryl C-H gave the fastest response to Pb(II) binding at lower pH and IS (e.g., pH 4.7 and IS = 0.01 M), followed by carboxyl C=O and polysaccharide C-OH and then chromophoric groups at 265 nm (CDOM265). However, the CDOM265 bound to Pb(II) prior to aryl C-H and polysaccharide C-OH groups at higher pH and IS (6.0 and 0.1 M, respectively), showing that the binding sequences were highly dependent on solution chemistry. Differential spectra combined with two dimensional UV-FTIR heterospectral correlation analysis can be used as a promising approach to elucidate metal-DOM interaction processes, including site heterogeneity, binding sensitivity and sequence at the functional group level. (C) 2018 Elsevier Ltd. All rights reserved.
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