Fractionation of water-soluble organic matter (WSOM) with polyvinylpyrrolidone: A study on antimony associated with WSOM in contaminated soils

Abstract

Water-soluble organic matter (WSOM) significantly influences the transport of metals and organic contaminants in soils, yet the interaction specifics with antimony (Sb) remain largely unexplored. Antimony is of particular environmental concern due to its toxic properties and harmful effects on ecosystems and human health. Employing a three-step fractionation method with polyvinylpyrrolidone (PVP), this study aimed to isolate and analyze humic acids (HA), PVP-non adsorbed fulvic acids (FAA), and PVP-adsorbed fulvic acids (FAB) from WSOM in soil spiked with Sb and incubated for 18 months. These fractions underwent chemical analysis for carbon (C), nitrogen (N), total organic carbon (TOC), and Sb, complemented by FTIR and 1H NMR spectroscopic characterization. The study revealed that HA was more aliphatic, with Sb predominantly associating with the fulvic acid (FA) fraction, accounting for 97 % of Sb in extracts. Specifically, the FAA subfraction held substantial portions of total carbon (TC), total nitrogen (TN), total organic carbon (TOC), and Sb. Correlations between Sb concentrations and TN, TC, and TOC were significant. Extraction methods showed NaOH and Na₄P₂O₇ outperformed HCl and deionised water in extracting TC, TN, and TOC, with higher Sb concentrations found in Na₄P₂O₇ and NaOH extracts. This underscores the role of Fe/Al-SOM complexes in Sb soil availability. The results revealed that FAA subfraction accounted for 76 %, 64 % and 94 % of TN, TOC and Sb, respectively. Therefore, this research highlights the FAA fraction's central role, predominantly comprising non-humic substances like amines, in the availability of C, N, and Sb in Sb-impacted soils. The findings offer insights for environmental management and remediation strategies.