Binding strength of mercury (II) to different dissolved organic matter: The roles of DOM properties and sources

• Published in: The Science of the total environment Vol. 807; no. Pt 3; p. 150979
• Main Authors: Wang, Yuqin, Liu, Jiang, Liem-Nguyen, Van, Tian, Shanyi, Zhang, Siqi, Wang, Dingyong, Jiang, Tao
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 10.02.2022
• Subjects: Binding constant; Characterization; Complexation; Dissolved Organic Matter; Equilibrium dialysis ligand exchange; Mercury; Spectrometry, Fluorescence; Characterization; Complexation; Dissolved organic matter; Mercury; Equilibrium dialysis ligand exchange; Binding constant
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2021.150979

Dissolved organic matter (DOM) influences the environmental fate and toxic effects of trace metals such as mercury (Hg). However, because of limits in DOM analytical techniques and lack of sample diversity in past studies, it remains unclear whether the binding strength of DOM complexed with Hg(II) is related to the DOM properties. In this study, different DOM isolates (n = 26) from various sources were used to determine the conditional stability constant (logK) of DOM-Hg complexes using the equilibrium dialysis ligand exchange (EDLE) method. UV–Vis and fluorescence spectrometry were used to evaluate the correlation between logK values and DOM properties, such as chromophoric moieties, aromaticity, and molecular weight. Results demonstrated that the DOM from different sources presented an extensive range of binding strengths to Hg(II), because of their heterogeneous properties. Moreover, DOM chromophores, including aromaticity and molecular weight, are critical indicators of the DOM-Hg affinity in ambient-relevant circumstances. Significantly, higher terrestrial DOM led to greater DOM-Hg affinity. Additionally, this study supports that UV–Vis and fluorescence spectroscopy can be used to estimate DOM composition and its binding strength with Hg(II). Furthermore, the observed relationship between logK and DOM properties provided a possible pathway of explanation for the spatial co-variations between Hg(II) concentrations and DOM characters observed in previous field investigations. [Display omitted] •Binding constant (logK) of DOM-Hg varies according to DOM sources.•Higher fraction of terrestrial DOM leads to a greater binding affinity for Hg(II).•Colored DOM is a critical indicator for the DOM-Hg binding strength.•Optical properties of DOM can be used to predict DOM-Hg affinity.•Aromaticity is crucial factor to explain higher logK of terrestrial-dominant DOM.