Molecular insight into the adsorption and fractionation distinction of algae and humus-derived dissolved organic matter induced by ferrihydrite

Authors: SOU, CHENGYU - University Of Science And Technology Beijing; ZHAO, WENSI - Chinese Research Academy Of Environmental Sciences; LIU, SHASHA - University Of Science And Technology Beijing; FU, RUI - University Of Science And Technology Beijing; REN, YI - University Of Science And Technology Beijing; QIU, YUE - University Of Science And Technology Beijing; ZHANG, YUXIN - University Of Science And Technology Beijing; He, Zhongqi; XING, BAOSHAN - University Of Massachusetts, Amherst; WU, FENGCHANG - Chinese Research Academy Of Environmental Sciences

Submitted to: Chemical Engineering Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/7/2024
Publication Date: 6/15/2024
Citation: Sou, C., Zhao, W., Liu, S., Fu, R., Ren, Y., Qiu, Y., Zhang, Y., He, Z., Xing, B., Wu, F. 2024. Molecular insight into the adsorption and fractionation distinction of algae and humus-derived dissolved organic matter induced by ferrihydrite. Chemical Engineering Journal. 494. Article 152960. https://doi.org/10.1016/j.cej.2024.152960.
DOI: https://doi.org/10.1016/j.cej.2024.152960

Interpretive Summary: Dissolved organic matter (DOM) is a complex mixture of heterogeneity, diversity and continuous variability with a variety of organic components, which ubiquitously present in natural waters. It is one of the largest active carbon pools on Earth and, thus an important component of the global carbon cycle. While the adsorption of allochthonous humic DOM on mineral have been extensively studied, the molecular-level adsorption of freshly produced algae-derived DOM (ADOM) is not fully understood. Here, in this work, the adsorption differences and molecular fractionation mechanisms of two typical types of DOMs (ADOM and SRFA) mediated by ferrihydrite in the ambient concentration range were investigated by optical spectroscopy (UV-Vis and EEM) and FT-ICR-MS. The resulted data suggested that the quantity and quality of settled DOM through ferrihydrite adsorption in water-sediment interface could be altered accompanying with more ADOM released in eutrophic lakes.

Technical Abstract: The mineral-induced adsorption of dissolved organic matter (DOM) occurred ubiquitously and is essential for carbon preservation in aquatic ecosystems. The adsorption of allochthonous humic DOM on mineral have been extensively studied, yet the molecular-level adsorption of freshly produced algae-derived DOM (ADOM) is not fully understood. Here, we investigated the ferrihydrite-induced adsorption of both ADOM and humic DOM using optical spectroscopy and high-resolution mass spectrometry. ADOM showed higher adsorption rate but lower saturation adsorption capacity than humic DOM. Optical spectra and mass spectrometry indicated large molecular weight (> 350 Da), high unsaturated and high oxygen-containing materials were preferentially adsorbed both for ADOM and humic DOM. However, their distinct molecular composition caused predominant adsorption of tannin-like and condensed aromatics in humic DOM and protein substances in ADOM. Moreover, the poor specificity of hydrophobic interaction for aliphatic compounds reduced the selective fractionation of ferrihydrite in ADOM, while the strong complexation of carboxyl and phenolic hydroxyl caused strong molecular fractionation for humic DOM. We thus conclude that ferrihydrite-induced adsorption was highly dependent on DOM origins and specific molecular composition. This suggests the potential changes of the quantity and quality of settled DOM through ferrihydrite adsorption in water-sediment interface accompanying with more ADOM released in eutrophic lakes.