Photobleaching affects the carbon sequestration of dissolved black carbon on ferrihydrite: Perspective from molecular fractionation

Leiye Sun; Pingxiao Wu; Tianming Wang; Jiayan Wu; Meiqing Chen; Zhongbo Shang; Zhi Dang; Nengwu Zhu

doi:10.1016/j.scitotenv.2023.168322

Photobleaching affects the carbon sequestration of dissolved black carbon on ferrihydrite: Perspective from molecular fractionation

Sci Total Environ. 2024 Jan 15:908:168322. doi: 10.1016/j.scitotenv.2023.168322. Epub 2023 Nov 7.

Authors

Leiye Sun¹, Pingxiao Wu², Tianming Wang¹, Jiayan Wu¹, Meiqing Chen¹, Zhongbo Shang¹, Zhi Dang³, Nengwu Zhu³

Affiliations

¹ School of Environment and Energy, South China University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 510006, China.
² School of Environment and Energy, South China University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 510006, China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, Guangzhou 510006, China; Guangdong Provincial Key Laboratory of Solid Wastes Pollution Control and Recycling, Guangzhou 510006, China; Guangdong Engineering and Technology Research Center for Environmental Nanomaterials, Guangzhou 510006, China. Electronic address: pppxwu@scut.edu.cn.
³ School of Environment and Energy, South China University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 510006, China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, Guangzhou 510006, China; Guangdong Provincial Key Laboratory of Solid Wastes Pollution Control and Recycling, Guangzhou 510006, China; Guangdong Engineering and Technology Research Center for Environmental Nanomaterials, Guangzhou 510006, China.

PMID: 37939941
DOI: 10.1016/j.scitotenv.2023.168322

Abstract

Photobleaching generally changes the structure and properties of dissolved black carbon (DBC), which further affects distribution of DBC at mineral-water interface. Here, we investigated the effect mechanism by which DBC photobleaching on its sequestration on ferrihydrite (Fh) from perspective of molecular fractionation. Results indicated that continuous sunlight irradiation led to the photolysis of aromatic humic- and fulvic-like components and the carboxylation of the functional structure. DBC could be considerably sequestered on the Fh surface, and photobleached DBC (pDBC) with longer sunlight irradiation durations had lower adsorption capacity on Fh. The photo-absorption and photo-activity ability of residual DBC/pDBCs after adsorption significantly weakened, indicating that the photo-liable components with great photochemical properties were preferentially sequestered on Fh during adsorption fractionation at Fh-water interface. Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) results showed high molecular weight, high O contents and high unsaturation compounds (such as polycyclic aromatics and polyphenols) were preferentially sequestered on Fh through ligand exchange between iron-coordinated hydroxyl and substituted carboxyl/hydroxyl in DBC. Among high unsaturation compounds, aromatic ring structures (C=C) were with greater affinity with Fh surface than CO in carboxyl/ester/quinone. Photobleaching caused the decrease in aromatic ring structures and the increase in CO in carboxyl, which was the key for weakening of sequestration of pDBC on Fh. Our findings prove that the photo-liable components of DBC are more tend to be sequestered on mineral, and promote the understanding of geochemical behavior of DBC in the solid earth interfaces.

Keywords: Carbon sequestration; Dissolved black carbon; Ferrihydrite; Fractionation; Photobleaching.