How do drying-wetting cycles influence availability of heavy metals in sediment? A perspective from DOM molecular composition

• Published in: Water research (Oxford) Vol. 220; p. 118671
• Main Authors: Huang, Mei, Zhou, Mi, Li, Zhongwu, Ding, Xiang, Wen, Jiajun, Jin, Changsheng, Wang, Lei, Xiao, Linhui, Chen, Jia
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 15.07.2022
• Subjects: Dissolved organic matter; Drying-wetting cycle; Heavy metals; lignin; mass spectrometry; Molecular composition; molecular weight; rivers; Sediment; sediments; stoichiometry; water; Dissolved organic matter; Sediment; Drying-wetting cycle; Molecular composition; Heavy metals
• ISSN: 0043-1354; 1879-2448; 1879-2448
• DOI: 10.1016/j.watres.2022.118671

•Drying-wetting cycles help to retain high aromatic and molecular weight DOM.•The proportion of condensed aromatics increased by 7% after drying-wetting cycles.•Availability of Cd had higher sensibility to dry-wet cycles than that of others.•Available Cd decreasing was related to an increase in aromatic and hydrophobic DOM. Investigating the influence mechanism of drying-wetting cycles on the availability and mobility of heavy metals in sediment from the perspective of the molecular composition of dissolved organic matter (DOM) may gain a new understanding, but little current information exists. Here, we used spectral technologies, high-resolution mass spectrometry, and elemental stoichiometry method to trace the change rules of the molecular composition of DOM in the riparian sediment of the river. Results showed that the drying-wetting cycles could benefit the degradation of labile fractions (e.g., proteins, aliphatics, and lipids) of DOM and retain the fractions with high aromaticity and molecular size (e.g., lignin). The decrease in the availability of Cd after drying-wetting alternation processes was highly related to these changes in DOM composition. However, the availability of Zn and Cu remained almost unchanged, which probably resulted from the release and depletion of N and S in sediment-derived DOM under drying-wetting alternation conditions. As for Cr, its exchangeable fraction was unchanged during the drying-wetting alternation process, likely due to its high stability in the sediment. These results have implications on the environmental geochemical cycling of heavy metals in the riparian sediment with frequent drying-wetting alternation. [Display omitted]