The spectral characteristics and cadmium complexation of soil dissolved organic matter in a wide range of forest lands

Xiaoqing Zhang; Ya Li; Jun Ye; Zhihua Chen; Dajun Ren; Shuqin Zhang

doi:10.1016/j.envpol.2022.118834

The spectral characteristics and cadmium complexation of soil dissolved organic matter in a wide range of forest lands

Environ Pollut. 2022 Apr 15:299:118834. doi: 10.1016/j.envpol.2022.118834. Epub 2022 Jan 11.

Authors

Xiaoqing Zhang¹, Ya Li², Jun Ye³, Zhihua Chen⁴, Dajun Ren¹, Shuqin Zhang¹

Affiliations

¹ College of Resource and Environmental Engineering, Wuhan University of Science and Technology, Wuhan, 430081, China; Hubei Key Laboratory for Efficient Utilization and Agglomeration of Metallurgic Mineral Resources, Wuhan University of Science and Technology, Wuhan, Hubei, 430081, China.
² College of Resource and Environmental Engineering, Wuhan University of Science and Technology, Wuhan, 430081, China.
³ Shiyan of Hubei Province Environmental Monitoring Center, Shiyan, Hubei, 442000, China. Electronic address: 15671601162@163.com.
⁴ School of Environment, Henan Normal University, Key Laboratory for Yellow River and Huai River Water Environment and Pollution Control, Xinxiang, 453007, China.

PMID: 35031407
DOI: 10.1016/j.envpol.2022.118834

Abstract

The quality and quantity of dissolved organic matter (DOM) greatly controls the fate of heavy metals. The characteristics of DOM and its interaction with metals are essential for the metal ecological risk assessment of soils. In this study, the DOM spectral characteristics of representative forest soils and the complex capacities between fluorescent DOM components and cadmium (Cd) were analyzed. Functional groups, such as carboxylic acids, alcohols and phenols, were determined by FT-IR analysis. Chromophoric DOM, fluorescent DOM and dissolved organic carbon (DOC) concentrations exhibited strong correlations with each other, indicating that variations of DOC could be well explained by Chromophoric DOM or fluorescent DOM due to high correlation coefficients. The spectral slope ratio was in the range of 0.85-5.90, implying an abundance of heavy macromolecular humic acids, peptides, and polycondensates. The absorbance spectral at 254 nm (SUVA₂₅₄) strongly correlated with SUVA₂₆₀ (r = 0.992, P < 0.01), indicating that hydrophobicity closely related with aromatic structure, and aromatic groups could be broadly hydrophobic. Fluorescence indices were from 1.62 to 2.21 and biological index values ranged from 0.54 to 1.14, where the DOM was mainly sourced from mixed terrestrial and autogenous inputs in most sites. Four universal fluorescence components were identified and characterized by fluorescence EEM-PARAFAC, including two humic-like (components 1 and 2), one tyrosine-like (components 3) and one fulvic-like (components 4) component. Both components 3 and 4 showed fluorescence quenching with increasing Cd concentrations, while components 1 and 2 had no evident change in fluorescence intensity. The logK₃ and logK₄ values ranged from 4.41 to 5.29 and 4.71 to 5.54, respectively, with most logK values of component 3 for Cd binding being smaller than that of component 4, thus, indicating that the fulvic acid substances exhibited stronger and more stable interactions with Cd than protein-like components.

Keywords: Cadmium; Dissolved organic matter; Parallel factor analysis; Soil properties; Spectrum characteristics.

MeSH terms

Cadmium / analysis
Dissolved Organic Matter
Forests
Humic Substances / analysis
Metals, Heavy* / analysis
Soil* / chemistry
Spectrometry, Fluorescence
Spectroscopy, Fourier Transform Infrared

Substances

Dissolved Organic Matter
Humic Substances
Metals, Heavy
Soil
Cadmium